From 12a0facff6a8215d73b9a297d4ac44d52ccb5ed8 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 18 Aug 2022 13:32:30 -0700
Subject: [PATCH 01/35] Make publish use internal buffers

---
 source/core_mqtt.c                    | 148 ++++++++++++++++----------
 source/core_mqtt_serializer.c         |  73 +++++++++++++
 source/include/core_mqtt_serializer.h |  28 +++++
 3 files changed, 190 insertions(+), 59 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 4226a7372..981e9f31e 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -232,20 +232,6 @@ static MQTTStatus_t validateSubscribeUnsubscribeParams( const MQTTContext_t * pC
                                                         size_t subscriptionCount,
                                                         uint16_t packetId );
 
-/**
- * @brief Send serialized publish packet using transport send.
- *
- * @brief param[in] pContext Initialized MQTT context.
- * @brief param[in] pPublishInfo MQTT PUBLISH packet parameters.
- * @brief param[in] headerSize Header size of the PUBLISH packet.
- *
- * @return #MQTTSendFailed if transport write failed;
- * #MQTTSuccess otherwise.
- */
-static MQTTStatus_t sendPublish( MQTTContext_t * pContext,
-                                 const MQTTPublishInfo_t * pPublishInfo,
-                                 size_t headerSize );
-
 /**
  * @brief Receives a CONNACK MQTT packet.
  *
@@ -280,6 +266,26 @@ static MQTTStatus_t receiveConnack( const MQTTContext_t * pContext,
 static MQTTStatus_t handleSessionResumption( MQTTContext_t * pContext,
                                              bool sessionPresent );
 
+
+/**
+ * @brief Send the publish packet without copying the topic string and payload in
+ * the buffer.
+ *
+ * @brief param[in] pContext Initialized MQTT context.
+ * @brief param[in] pPublishInfo MQTT PUBLISH packet parameters.
+ * @brief param[in] pMqttHeader the serialized MQTT header with the header byte;
+ * the encoded length of the packet; and the encoded length of the topic string.
+ * @brief param[in] headerSize Size of the serialized PUBLISH header.
+ * @brief param[in] packetId Packet Id of the publish packet.
+ *
+ * @return #MQTTSendFailed if transport send during resend failed;
+ * #MQTTSuccess otherwise.
+ */
+static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
+                                            const MQTTPublishInfo_t * pPublishInfo,
+                                            const uint8_t * pMqttHeader,
+                                            size_t headerSize,
+                                            uint16_t packetId );
 /**
  * @brief Serializes a PUBLISH message.
  *
@@ -1412,56 +1418,69 @@ static MQTTStatus_t validateSubscribeUnsubscribeParams( const MQTTContext_t * pC
 
 /*-----------------------------------------------------------*/
 
-static MQTTStatus_t sendPublish( MQTTContext_t * pContext,
-                                 const MQTTPublishInfo_t * pPublishInfo,
-                                 size_t headerSize )
+static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
+                                            const MQTTPublishInfo_t * pPublishInfo,
+                                            const uint8_t * pMqttHeader,
+                                            size_t headerSize,
+                                            uint16_t packetId )
 {
     MQTTStatus_t status = MQTTSuccess;
-    int32_t bytesSent = 0;
-
-    assert( pContext != NULL );
-    assert( pPublishInfo != NULL );
-    assert( headerSize > 0 );
-    assert( pContext->networkBuffer.pBuffer != NULL );
-    assert( !( pPublishInfo->payloadLength > 0 ) || ( pPublishInfo->pPayload != NULL ) );
+    int32_t bytesSent;
+    uint8_t serializedPacketID[ 2 ];
+    const size_t packetIdLength = 2UL;
 
-    /* Send header first. */
+    /* Send the serialized publish packet header over network. */
     bytesSent = sendPacket( pContext,
-                            pContext->networkBuffer.pBuffer,
+                            pMqttHeader,
                             headerSize );
 
-    if( bytesSent < ( int32_t ) headerSize )
+    if( bytesSent != ( int32_t ) headerSize )
     {
-        LogError( ( "Transport send failed for PUBLISH header." ) );
         status = MQTTSendFailed;
     }
-    else
+
+    if( status == MQTTSuccess )
     {
-        LogDebug( ( "Sent %ld bytes of PUBLISH header.",
-                    ( long int ) bytesSent ) );
+        /* Send the topic string over the network. */
+        bytesSent = sendPacket( pContext,
+                                ( const uint8_t * ) pPublishInfo->pTopicName,
+                                pPublishInfo->topicNameLength );
 
-        /* Send Payload if there is one to send. It is valid for a PUBLISH
-         * Packet to contain a zero length payload.*/
-        if( pPublishInfo->payloadLength > 0U )
+        if( bytesSent != ( ( int32_t ) pPublishInfo->topicNameLength ) )
         {
-            bytesSent = sendPacket( pContext,
-                                    pPublishInfo->pPayload,
-                                    pPublishInfo->payloadLength );
+            status = MQTTSendFailed;
+        }
+    }
 
-            if( bytesSent < ( int32_t ) pPublishInfo->payloadLength )
-            {
-                LogError( ( "Transport send failed for PUBLISH payload." ) );
-                status = MQTTSendFailed;
-            }
-            else
-            {
-                LogDebug( ( "Sent %ld bytes of PUBLISH payload.",
-                            ( long int ) bytesSent ) );
-            }
+    if( ( status == MQTTSuccess ) && ( pPublishInfo->qos > MQTTQoS0 ) )
+    {
+        /* Encode and send the packet ID. */
+        serializedPacketID[ 0 ] = ( ( uint8_t ) ( ( packetId ) >> 8 ) );
+        serializedPacketID[ 1 ] = ( ( uint8_t ) ( ( packetId ) & 0x00ffU ) );
+
+        /* Sends the topic string over the network. */
+        bytesSent = sendPacket( pContext,
+                                serializedPacketID,
+                                packetIdLength );
+
+        if( bytesSent != ( int32_t ) packetIdLength )
+        {
+            status = MQTTSendFailed;
         }
-        else
+    }
+
+    if( ( status == MQTTSuccess ) &&
+        ( pPublishInfo->payloadLength > 0U ) )
+    {
+        /* Send Payload if there is one to send. It is valid for a PUBLISH
+         * Packet to contain a zero length payload.*/
+        bytesSent = sendPacket( pContext,
+                                pPublishInfo->pPayload,
+                                pPublishInfo->payloadLength );
+
+        if( bytesSent != ( ( int32_t ) pPublishInfo->payloadLength ) )
         {
-            LogDebug( ( "PUBLISH payload was not sent. Payload length was zero." ) );
+            status = MQTTSendFailed;
         }
     }
 
@@ -1929,19 +1948,29 @@ MQTTStatus_t MQTT_Publish( MQTTContext_t * pContext,
                            const MQTTPublishInfo_t * pPublishInfo,
                            uint16_t packetId )
 {
-    size_t headerSize = 0UL;
+    size_t headerSize = 0UL, remainingLength = 0UL, packetSize = 0UL;
     MQTTPublishState_t publishStatus = MQTTStateNull;
+    /* 1 header byte + 4 bytes (maximum) required for encoding the length +
+     * 2 bytes for topic string. */
+    uint8_t mqttHeader[ 7 ];
 
     /* Validate arguments. */
     MQTTStatus_t status = validatePublishParams( pContext, pPublishInfo, packetId );
 
     if( status == MQTTSuccess )
     {
-        /* Serialize PUBLISH packet. */
-        status = serializePublish( pContext,
-                                   pPublishInfo,
-                                   packetId,
-                                   &headerSize );
+        /* Get the remaining length and packet size.*/
+        status = MQTT_GetPublishPacketSize( pPublishInfo,
+                                            &remainingLength,
+                                            &packetSize );
+    }
+
+    if( status == MQTTSuccess )
+    {
+        status = MQTT_SerializePublishHeaderWithoutTopic( pPublishInfo,
+                                                          remainingLength,
+                                                          mqttHeader,
+                                                          &headerSize );
     }
 
     if( ( status == MQTTSuccess ) && ( pPublishInfo->qos > MQTTQoS0 ) )
@@ -1962,10 +1991,11 @@ MQTTStatus_t MQTT_Publish( MQTTContext_t * pContext,
 
     if( status == MQTTSuccess )
     {
-        /* Sends the serialized publish packet over network. */
-        status = sendPublish( pContext,
-                              pPublishInfo,
-                              headerSize );
+        status = sendPublishWithoutCopy( pContext,
+                                         pPublishInfo,
+                                         mqttHeader,
+                                         headerSize,
+                                         packetId );
     }
 
     if( ( status == MQTTSuccess ) && ( pPublishInfo->qos > MQTTQoS0 ) )
diff --git a/source/core_mqtt_serializer.c b/source/core_mqtt_serializer.c
index cfc1f00d3..000e6e2a5 100644
--- a/source/core_mqtt_serializer.c
+++ b/source/core_mqtt_serializer.c
@@ -612,6 +612,79 @@ static bool calculatePublishPacketSize( const MQTTPublishInfo_t * pPublishInfo,
 
 /*-----------------------------------------------------------*/
 
+MQTTStatus_t MQTT_SerializePublishHeaderWithoutTopic( const MQTTPublishInfo_t * pPublishInfo,
+                                                      size_t remainingLength,
+                                                      uint8_t * pBuffer,
+                                                      size_t * headerSize )
+{
+    size_t headerLength;
+    uint8_t * pIndex;
+    MQTTStatus_t status = MQTTSuccess;
+
+    /* The first byte of a PUBLISH packet contains the packet type and flags. */
+    uint8_t publishFlags = MQTT_PACKET_TYPE_PUBLISH;
+
+    /* Get the start address of the buffer. */
+    pIndex = pBuffer;
+
+    /* Length of serialized packet = First byte
+     *                               + Length of encoded remaining length
+     *                               + Encoded topic length. */
+    headerLength = 1U + remainingLengthEncodedSize( remainingLength ) + 2U;
+
+    if( pPublishInfo->qos == MQTTQoS1 )
+    {
+        LogDebug( ( "Adding QoS as QoS1 in PUBLISH flags." ) );
+        UINT8_SET_BIT( publishFlags, MQTT_PUBLISH_FLAG_QOS1 );
+    }
+    else if( pPublishInfo->qos == MQTTQoS2 )
+    {
+        LogDebug( ( "Adding QoS as QoS2 in PUBLISH flags." ) );
+        UINT8_SET_BIT( publishFlags, MQTT_PUBLISH_FLAG_QOS2 );
+    }
+    else
+    {
+        /* Empty else MISRA 15.7 */
+    }
+
+    if( pPublishInfo->retain == true )
+    {
+        LogDebug( ( "Adding retain bit in PUBLISH flags." ) );
+        UINT8_SET_BIT( publishFlags, MQTT_PUBLISH_FLAG_RETAIN );
+    }
+
+    if( pPublishInfo->dup == true )
+    {
+        LogDebug( ( "Adding dup bit in PUBLISH flags." ) );
+        UINT8_SET_BIT( publishFlags, MQTT_PUBLISH_FLAG_DUP );
+    }
+
+    *pIndex = publishFlags;
+    pIndex++;
+
+    /* The "Remaining length" is encoded from the second byte. */
+    pIndex = encodeRemainingLength( pIndex, remainingLength );
+
+    /* The first byte of a UTF-8 string is the high byte of the string length. */
+    *pIndex = UINT16_HIGH_BYTE( pPublishInfo->topicNameLength );
+    pIndex++;
+
+    /* The second byte of a UTF-8 string is the low byte of the string length. */
+    *pIndex = UINT16_LOW_BYTE( pPublishInfo->topicNameLength );
+    pIndex++;
+
+    *headerSize = headerLength;
+
+    if( headerLength > 7 )
+    {
+        status = MQTTBadParameter;
+    }
+
+    return status;
+}
+
+/*-----------------------------------------------------------*/
+
 static void serializePublishCommon( const MQTTPublishInfo_t * pPublishInfo,
                                     size_t remainingLength,
                                     uint16_t packetIdentifier,
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index bf3d974f4..2a6c8e9f5 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -738,6 +738,34 @@ MQTTStatus_t MQTT_SerializePublish( const MQTTPublishInfo_t * pPublishInfo,
                                     const MQTTFixedBuffer_t * pFixedBuffer );
 /* @[declare_mqtt_serializepublish] */
 
+/* TODO: Re-write the brief comments below. */
+/**
+ * @brief Serialize an MQTT PUBLISH packet header without the topic string in the
+ * given buffer. This function will add the topic string length to the provided
+ * buffer. This helps reduce an unnecessary copy of the topic string into the
+ * buffer.
+ *
+ * #MQTT_GetPublishPacketSize should be called with @p pPublishInfo before
+ * invoking this function to get the size of the required buffer and
+ * @p remainingLength. The @p remainingLength must be the same as returned by
+ * #MQTT_GetPublishPacketSize. The buffer must be at least as large
+ * as the size returned by #MQTT_GetPublishPacketSize.
+ *
+ * @param[in] pPublishInfo MQTT PUBLISH packet parameters.
+ * @param[in] packetId packet ID generated by #MQTT_GetPacketId.
+ * @param[in] remainingLength Remaining Length provided by #MQTT_GetPublishPacketSize.
+ * @param[out] pFixedBuffer Buffer for packet serialization.
+ * @param[out] pHeaderSize Size of the serialized MQTT PUBLISH header.
+ *
+ * @return #MQTTNoMemory if pFixedBuffer is too small to hold the MQTT packet;
+ * #MQTTBadParameter if invalid parameters are passed;
+ * #MQTTSuccess otherwise.
+ */
+MQTTStatus_t MQTT_SerializePublishHeaderWithoutTopic( const MQTTPublishInfo_t * pPublishInfo,
+                                                      size_t remainingLength,
+                                                      uint8_t * pBuffer,
+                                                      size_t * headerSize );
+
 /**
  * @brief Serialize an MQTT PUBLISH packet header in the given buffer.
  *

From 00f0b5889e15ff7bcdfe349d82e80e2f25e29c0d Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 18 Aug 2022 14:39:09 -0700
Subject: [PATCH 02/35] Fix comment about packet ID

---
 source/core_mqtt.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 981e9f31e..becdba59a 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -1454,11 +1454,11 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
 
     if( ( status == MQTTSuccess ) && ( pPublishInfo->qos > MQTTQoS0 ) )
     {
-        /* Encode and send the packet ID. */
+        /* Encode the packet ID. */
         serializedPacketID[ 0 ] = ( ( uint8_t ) ( ( packetId ) >> 8 ) );
         serializedPacketID[ 1 ] = ( ( uint8_t ) ( ( packetId ) & 0x00ffU ) );
 
-        /* Sends the topic string over the network. */
+        /* Send the packet ID over the network. */
         bytesSent = sendPacket( pContext,
                                 serializedPacketID,
                                 packetIdLength );

From 24a1a3ea72877ad563949a2b487505af31888a86 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 18 Aug 2022 15:52:12 -0700
Subject: [PATCH 03/35] Try a different approach for ping and disconnect

---
 source/core_mqtt.c                    |  19 ++++-
 source/core_mqtt_serializer.c         | 110 --------------------------
 source/include/core_mqtt_serializer.h | 110 ++++++++++++++++++++++++++
 3 files changed, 125 insertions(+), 114 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index becdba59a..bba708b01 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -2034,6 +2034,12 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
     int32_t bytesSent = 0;
     MQTTStatus_t status = MQTTSuccess;
     size_t packetSize = 0U;
+    /* MQTT ping packets are of fixed length. */
+    uint8_t pingreqPacket[ MQTT_PACKET_PINGREQ_SIZE ];
+    MQTTFixedBuffer_t localBuffer;
+
+    localBuffer.pBuffer = pingreqPacket;
+    localBuffer.size = MQTT_PACKET_PINGREQ_SIZE;
 
     if( pContext == NULL )
     {
@@ -2060,14 +2066,14 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
     if( status == MQTTSuccess )
     {
         /* Serialize MQTT PINGREQ. */
-        status = MQTT_SerializePingreq( &( pContext->networkBuffer ) );
+        status = MQTT_SerializePingreq( &localBuffer );
     }
 
     if( status == MQTTSuccess )
     {
         /* Send the serialized PINGREQ packet to transport layer. */
         bytesSent = sendPacket( pContext,
-                                pContext->networkBuffer.pBuffer,
+                                localBuffer.pBuffer,
                                 packetSize );
 
         /* It is an error to not send the entire PINGREQ packet. */
@@ -2155,6 +2161,11 @@ MQTTStatus_t MQTT_Disconnect( MQTTContext_t * pContext )
     size_t packetSize = 0U;
     int32_t bytesSent = 0;
     MQTTStatus_t status = MQTTSuccess;
+    MQTTFixedBuffer_t localBuffer;
+    uint8_t disconnectPacket[ MQTT_DISCONNECT_PACKET_SIZE ];
+
+    localBuffer.pBuffer = disconnectPacket;
+    localBuffer.size = MQTT_DISCONNECT_PACKET_SIZE;
 
     /* Validate arguments. */
     if( pContext == NULL )
@@ -2174,13 +2185,13 @@ MQTTStatus_t MQTT_Disconnect( MQTTContext_t * pContext )
     if( status == MQTTSuccess )
     {
         /* Serialize MQTT DISCONNECT packet. */
-        status = MQTT_SerializeDisconnect( &( pContext->networkBuffer ) );
+        status = MQTT_SerializeDisconnect( &localBuffer );
     }
 
     if( status == MQTTSuccess )
     {
         bytesSent = sendPacket( pContext,
-                                pContext->networkBuffer.pBuffer,
+                                localBuffer.pBuffer,
                                 packetSize );
 
         if( bytesSent < ( int32_t ) packetSize )
diff --git a/source/core_mqtt_serializer.c b/source/core_mqtt_serializer.c
index 000e6e2a5..f228460bd 100644
--- a/source/core_mqtt_serializer.c
+++ b/source/core_mqtt_serializer.c
@@ -30,116 +30,6 @@
 #include "core_mqtt_serializer.h"
 #include "core_mqtt_default_logging.h"
 
-/**
- * @brief MQTT protocol version 3.1.1.
- */
-#define MQTT_VERSION_3_1_1                          ( ( uint8_t ) 4U )
-
-/**
- * @brief Size of the fixed and variable header of a CONNECT packet.
- */
-#define MQTT_PACKET_CONNECT_HEADER_SIZE             ( 10UL )
-
-/* MQTT CONNECT flags. */
-#define MQTT_CONNECT_FLAG_CLEAN                     ( 1 ) /**< @brief Clean session. */
-#define MQTT_CONNECT_FLAG_WILL                      ( 2 ) /**< @brief Will present. */
-#define MQTT_CONNECT_FLAG_WILL_QOS1                 ( 3 ) /**< @brief Will QoS 1. */
-#define MQTT_CONNECT_FLAG_WILL_QOS2                 ( 4 ) /**< @brief Will QoS 2. */
-#define MQTT_CONNECT_FLAG_WILL_RETAIN               ( 5 ) /**< @brief Will retain. */
-#define MQTT_CONNECT_FLAG_PASSWORD                  ( 6 ) /**< @brief Password present. */
-#define MQTT_CONNECT_FLAG_USERNAME                  ( 7 ) /**< @brief User name present. */
-
-/*
- * Positions of each flag in the first byte of an MQTT PUBLISH packet's
- * fixed header.
- */
-#define MQTT_PUBLISH_FLAG_RETAIN                    ( 0 ) /**< @brief MQTT PUBLISH retain flag. */
-#define MQTT_PUBLISH_FLAG_QOS1                      ( 1 ) /**< @brief MQTT PUBLISH QoS1 flag. */
-#define MQTT_PUBLISH_FLAG_QOS2                      ( 2 ) /**< @brief MQTT PUBLISH QoS2 flag. */
-#define MQTT_PUBLISH_FLAG_DUP                       ( 3 ) /**< @brief MQTT PUBLISH duplicate flag. */
-
-/**
- * @brief The size of MQTT DISCONNECT packets, per MQTT spec.
- */
-#define MQTT_DISCONNECT_PACKET_SIZE                 ( 2UL )
-
-/**
- * @brief A PINGREQ packet is always 2 bytes in size, defined by MQTT 3.1.1 spec.
- */
-#define MQTT_PACKET_PINGREQ_SIZE                    ( 2UL )
-
-/**
- * @brief The Remaining Length field of MQTT disconnect packets, per MQTT spec.
- */
-#define MQTT_DISCONNECT_REMAINING_LENGTH            ( ( uint8_t ) 0 )
-
-/*
- * Constants relating to CONNACK packets, defined by MQTT 3.1.1 spec.
- */
-#define MQTT_PACKET_CONNACK_REMAINING_LENGTH        ( ( uint8_t ) 2U )    /**< @brief A CONNACK packet always has a "Remaining length" of 2. */
-#define MQTT_PACKET_CONNACK_SESSION_PRESENT_MASK    ( ( uint8_t ) 0x01U ) /**< @brief The "Session Present" bit is always the lowest bit. */
-
-/*
- * UNSUBACK, PUBACK, PUBREC, PUBREL, and PUBCOMP always have a remaining length
- * of 2.
- */
-#define MQTT_PACKET_SIMPLE_ACK_REMAINING_LENGTH     ( ( uint8_t ) 2 ) /**< @brief PUBACK, PUBREC, PUBREl, PUBCOMP, UNSUBACK Remaining length. */
-#define MQTT_PACKET_PINGRESP_REMAINING_LENGTH       ( 0U )            /**< @brief A PINGRESP packet always has a "Remaining length" of 0. */
-
-/**
- * @brief Per the MQTT 3.1.1 spec, the largest "Remaining Length" of an MQTT
- * packet is this value, 256 MB.
- */
-#define MQTT_MAX_REMAINING_LENGTH                   ( 268435455UL )
-
-/**
- * @brief Set a bit in an 8-bit unsigned integer.
- */
-#define UINT8_SET_BIT( x, position )      ( ( x ) = ( uint8_t ) ( ( x ) | ( 0x01U << ( position ) ) ) )
-
-/**
- * @brief Macro for checking if a bit is set in a 1-byte unsigned int.
- *
- * @param[in] x The unsigned int to check.
- * @param[in] position Which bit to check.
- */
-#define UINT8_CHECK_BIT( x, position )    ( ( ( x ) & ( 0x01U << ( position ) ) ) == ( 0x01U << ( position ) ) )
-
-/**
- * @brief Get the high byte of a 16-bit unsigned integer.
- */
-#define UINT16_HIGH_BYTE( x )             ( ( uint8_t ) ( ( x ) >> 8 ) )
-
-/**
- * @brief Get the low byte of a 16-bit unsigned integer.
- */
-#define UINT16_LOW_BYTE( x )              ( ( uint8_t ) ( ( x ) & 0x00ffU ) )
-
-/**
- * @brief Macro for decoding a 2-byte unsigned int from a sequence of bytes.
- *
- * @param[in] ptr A uint8_t* that points to the high byte.
- */
-#define UINT16_DECODE( ptr )                                \
-    ( uint16_t ) ( ( ( ( uint16_t ) ( *( ptr ) ) ) << 8 ) | \
-                   ( ( uint16_t ) ( *( ( ptr ) + 1 ) ) ) )
-
-/**
- * @brief A value that represents an invalid remaining length.
- *
- * This value is greater than what is allowed by the MQTT specification.
- */
-#define MQTT_REMAINING_LENGTH_INVALID             ( ( size_t ) 268435456 )
-
-/**
- * @brief The minimum remaining length for a QoS 0 PUBLISH.
- *
- * Includes two bytes for topic name length and one byte for topic name.
- */
-#define MQTT_MIN_PUBLISH_REMAINING_LENGTH_QOS0    ( 3U )
-
-/*-----------------------------------------------------------*/
-
 /**
  * @brief MQTT Subscription packet types.
  */
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 2a6c8e9f5..c6088e37e 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -76,6 +76,116 @@
 #define MQTT_PACKET_TYPE_DISCONNECT     ( ( uint8_t ) 0xE0U )  /**< @brief DISCONNECT (client-to-server). */
 /** @} */
 
+/**
+ * @brief MQTT protocol version 3.1.1.
+ */
+#define MQTT_VERSION_3_1_1                          ( ( uint8_t ) 4U )
+
+/**
+ * @brief Size of the fixed and variable header of a CONNECT packet.
+ */
+#define MQTT_PACKET_CONNECT_HEADER_SIZE             ( 10UL )
+
+/* MQTT CONNECT flags. */
+#define MQTT_CONNECT_FLAG_CLEAN                     ( 1 ) /**< @brief Clean session. */
+#define MQTT_CONNECT_FLAG_WILL                      ( 2 ) /**< @brief Will present. */
+#define MQTT_CONNECT_FLAG_WILL_QOS1                 ( 3 ) /**< @brief Will QoS 1. */
+#define MQTT_CONNECT_FLAG_WILL_QOS2                 ( 4 ) /**< @brief Will QoS 2. */
+#define MQTT_CONNECT_FLAG_WILL_RETAIN               ( 5 ) /**< @brief Will retain. */
+#define MQTT_CONNECT_FLAG_PASSWORD                  ( 6 ) /**< @brief Password present. */
+#define MQTT_CONNECT_FLAG_USERNAME                  ( 7 ) /**< @brief User name present. */
+
+/*
+ * Positions of each flag in the first byte of an MQTT PUBLISH packet's
+ * fixed header.
+ */
+#define MQTT_PUBLISH_FLAG_RETAIN                    ( 0 ) /**< @brief MQTT PUBLISH retain flag. */
+#define MQTT_PUBLISH_FLAG_QOS1                      ( 1 ) /**< @brief MQTT PUBLISH QoS1 flag. */
+#define MQTT_PUBLISH_FLAG_QOS2                      ( 2 ) /**< @brief MQTT PUBLISH QoS2 flag. */
+#define MQTT_PUBLISH_FLAG_DUP                       ( 3 ) /**< @brief MQTT PUBLISH duplicate flag. */
+
+/**
+ * @brief The size of MQTT DISCONNECT packets, per MQTT spec.
+ */
+#define MQTT_DISCONNECT_PACKET_SIZE                 ( 2UL )
+
+/**
+ * @brief A PINGREQ packet is always 2 bytes in size, defined by MQTT 3.1.1 spec.
+ */
+#define MQTT_PACKET_PINGREQ_SIZE                    ( 2UL )
+
+/**
+ * @brief The Remaining Length field of MQTT disconnect packets, per MQTT spec.
+ */
+#define MQTT_DISCONNECT_REMAINING_LENGTH            ( ( uint8_t ) 0 )
+
+/*
+ * Constants relating to CONNACK packets, defined by MQTT 3.1.1 spec.
+ */
+#define MQTT_PACKET_CONNACK_REMAINING_LENGTH        ( ( uint8_t ) 2U )    /**< @brief A CONNACK packet always has a "Remaining length" of 2. */
+#define MQTT_PACKET_CONNACK_SESSION_PRESENT_MASK    ( ( uint8_t ) 0x01U ) /**< @brief The "Session Present" bit is always the lowest bit. */
+
+/*
+ * UNSUBACK, PUBACK, PUBREC, PUBREL, and PUBCOMP always have a remaining length
+ * of 2.
+ */
+#define MQTT_PACKET_SIMPLE_ACK_REMAINING_LENGTH     ( ( uint8_t ) 2 ) /**< @brief PUBACK, PUBREC, PUBREl, PUBCOMP, UNSUBACK Remaining length. */
+#define MQTT_PACKET_PINGRESP_REMAINING_LENGTH       ( 0U )            /**< @brief A PINGRESP packet always has a "Remaining length" of 0. */
+
+/**
+ * @brief Per the MQTT 3.1.1 spec, the largest "Remaining Length" of an MQTT
+ * packet is this value, 256 MB.
+ */
+#define MQTT_MAX_REMAINING_LENGTH                   ( 268435455UL )
+
+/**
+ * @brief Set a bit in an 8-bit unsigned integer.
+ */
+#define UINT8_SET_BIT( x, position )      ( ( x ) = ( uint8_t ) ( ( x ) | ( 0x01U << ( position ) ) ) )
+
+/**
+ * @brief Macro for checking if a bit is set in a 1-byte unsigned int.
+ *
+ * @param[in] x The unsigned int to check.
+ * @param[in] position Which bit to check.
+ */
+#define UINT8_CHECK_BIT( x, position )    ( ( ( x ) & ( 0x01U << ( position ) ) ) == ( 0x01U << ( position ) ) )
+
+/**
+ * @brief Get the high byte of a 16-bit unsigned integer.
+ */
+#define UINT16_HIGH_BYTE( x )             ( ( uint8_t ) ( ( x ) >> 8 ) )
+
+/**
+ * @brief Get the low byte of a 16-bit unsigned integer.
+ */
+#define UINT16_LOW_BYTE( x )              ( ( uint8_t ) ( ( x ) & 0x00ffU ) )
+
+/**
+ * @brief Macro for decoding a 2-byte unsigned int from a sequence of bytes.
+ *
+ * @param[in] ptr A uint8_t* that points to the high byte.
+ */
+#define UINT16_DECODE( ptr )                                \
+    ( uint16_t ) ( ( ( ( uint16_t ) ( *( ptr ) ) ) << 8 ) | \
+                   ( ( uint16_t ) ( *( ( ptr ) + 1 ) ) ) )
+
+/**
+ * @brief A value that represents an invalid remaining length.
+ *
+ * This value is greater than what is allowed by the MQTT specification.
+ */
+#define MQTT_REMAINING_LENGTH_INVALID             ( ( size_t ) 268435456 )
+
+/**
+ * @brief The minimum remaining length for a QoS 0 PUBLISH.
+ *
+ * Includes two bytes for topic name length and one byte for topic name.
+ */
+#define MQTT_MIN_PUBLISH_REMAINING_LENGTH_QOS0    ( 3U )
+
+/*-----------------------------------------------------------*/
+
 /**
  * @ingroup mqtt_constants
  * @brief The size of MQTT PUBACK, PUBREC, PUBREL, and PUBCOMP packets, per MQTT spec.

From a40d76837fd9125bc7c5c3b2f7d9e30ee7456a62 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Mon, 22 Aug 2022 13:05:48 -0700
Subject: [PATCH 04/35] Use writev and flush in conjuction with send

---
 source/core_mqtt.c                     | 82 ++++++++++++++++++++------
 source/interface/transport_interface.h | 45 ++++++++++++++
 2 files changed, 109 insertions(+), 18 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index bba708b01..e01b5f1b9 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -1428,23 +1428,48 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
     int32_t bytesSent;
     uint8_t serializedPacketID[ 2 ];
     const size_t packetIdLength = 2UL;
+    bool writeAndFlushAvailable;
+
+    writeAndFlushAvailable = ( ( pContext->transportInterface.write != NULL ) &&
+                             ( pContext->transportInterface.flush != NULL ) );
+
+    /* Encode the packet ID. */
+    serializedPacketID[ 0 ] = ( ( uint8_t ) ( ( packetId ) >> 8 ) );
+    serializedPacketID[ 1 ] = ( ( uint8_t ) ( ( packetId ) & 0x00ffU ) );
 
     /* Send the serialized publish packet header over network. */
-    bytesSent = sendPacket( pContext,
-                            pMqttHeader,
-                            headerSize );
+    if( writeAndFlushAvailable == true )
+    {
+        bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
+                                                        pMqttHeader,
+                                                        headerSize );
+    }
+    else
+    {
+        bytesSent = sendPacket( pContext,
+                                pMqttHeader,
+                                headerSize );
+    }
 
     if( bytesSent != ( int32_t ) headerSize )
     {
         status = MQTTSendFailed;
     }
-
-    if( status == MQTTSuccess )
+    else
     {
         /* Send the topic string over the network. */
-        bytesSent = sendPacket( pContext,
-                                ( const uint8_t * ) pPublishInfo->pTopicName,
-                                pPublishInfo->topicNameLength );
+        if( writeAndFlushAvailable == true )
+        {
+            bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
+                                                            ( const uint8_t* )pPublishInfo->pTopicName,
+                                                            pPublishInfo->topicNameLength );
+        }
+        else
+        {
+            bytesSent = sendPacket( pContext,
+                                    ( const uint8_t * ) pPublishInfo->pTopicName,
+                                    pPublishInfo->topicNameLength );
+        }
 
         if( bytesSent != ( ( int32_t ) pPublishInfo->topicNameLength ) )
         {
@@ -1454,14 +1479,19 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
 
     if( ( status == MQTTSuccess ) && ( pPublishInfo->qos > MQTTQoS0 ) )
     {
-        /* Encode the packet ID. */
-        serializedPacketID[ 0 ] = ( ( uint8_t ) ( ( packetId ) >> 8 ) );
-        serializedPacketID[ 1 ] = ( ( uint8_t ) ( ( packetId ) & 0x00ffU ) );
-
         /* Send the packet ID over the network. */
-        bytesSent = sendPacket( pContext,
-                                serializedPacketID,
-                                packetIdLength );
+        if( writeAndFlushAvailable == true )
+        {
+            bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
+                                                            serializedPacketID,
+                                                            packetIdLength );
+        }
+        else
+        {
+            bytesSent = sendPacket( pContext,
+                                    serializedPacketID,
+                                    packetIdLength );
+        }
 
         if( bytesSent != ( int32_t ) packetIdLength )
         {
@@ -1474,9 +1504,18 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
     {
         /* Send Payload if there is one to send. It is valid for a PUBLISH
          * Packet to contain a zero length payload.*/
-        bytesSent = sendPacket( pContext,
-                                pPublishInfo->pPayload,
-                                pPublishInfo->payloadLength );
+        if( writeAndFlushAvailable == true )
+        {
+            bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
+                                                            pPublishInfo->pPayload,
+                                                            pPublishInfo->payloadLength );
+        }
+        else
+        {
+            bytesSent = sendPacket( pContext,
+                                    pPublishInfo->pPayload,
+                                    pPublishInfo->payloadLength );
+        }
 
         if( bytesSent != ( ( int32_t ) pPublishInfo->payloadLength ) )
         {
@@ -1484,6 +1523,13 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
         }
     }
 
+    if( ( status == MQTTSuccess ) &&
+        ( writeAndFlushAvailable == true ) )
+    {
+        /* Flush the buffers to send the message over the network. */
+        ( void ) pContext->transportInterface.flush( pContext->transportInterface.pNetworkContext );
+    }
+
     return status;
 }
 
diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index e476945c6..3ad52f17a 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -243,6 +243,49 @@ typedef int32_t ( * TransportSend_t )( NetworkContext_t * pNetworkContext,
                                        size_t bytesToSend );
 /* @[define_transportsend] */
 
+/**
+ * @transportcallback
+ * @brief Transport interface for writing data into the IP stack's buffers. This
+ * data will not be sent immediately as the stack will wait for the application to
+ * write more data.
+ *
+ * @param[in] pNetworkContext Implementation-defined network context.
+ * @param[in] pBuffer Buffer containing the bytes to send over the network stack.
+ * @param[in] bytesToWrite Number of bytes to write to the stack's buffers.
+ *
+ * @return The number of bytes written or a negative value to indicate error.
+ *
+ * @note If no data is written to the buffer due to the buffer being full this MUST
+ * return zero as the return value.
+ * A zero return value SHOULD represent that the send operation can be retried
+ * by calling the API function. Zero MUST NOT be returned if a network disconnection
+ * has occurred.
+ */
+/* @[define_transportwrite] */
+typedef int32_t ( * TransportWrite_t )( NetworkContext_t * pNetworkContext,
+                                        const void * pBuffer,
+                                        size_t bytesToWrite );
+/* @[define_transportwrite] */
+
+/**
+ * @transportcallback
+ * @brief Transport interface for sending all the data present in the IP-stacks buffers
+ * added by the call to transport interface write function.
+ *
+ * @param[in] pNetworkContext Implementation-defined network context.
+ *
+ * @return The number of bytes sent or a negative value to indicate error.
+ *
+ * @note If no data is written to the buffer due to the buffer being full this MUST
+ * return zero as the return value.
+ * A zero return value SHOULD represent that the send operation can be retried
+ * by calling the API function. Zero MUST NOT be returned if a network disconnection
+ * has occurred.
+ */
+/* @[define_transportflush] */
+typedef int32_t ( * TransportFlush_t )( NetworkContext_t * pNetworkContext );
+/* @[define_transportflush] */
+
 /**
  * @transportstruct
  * @brief The transport layer interface.
@@ -252,6 +295,8 @@ typedef struct TransportInterface
 {
     TransportRecv_t recv;               /**< Transport receive interface. */
     TransportSend_t send;               /**< Transport send interface. */
+    TransportWrite_t write;             /**< Transport write interface. */
+    TransportFlush_t flush;             /**< Transport flush interface. */
     NetworkContext_t * pNetworkContext; /**< Implementation-defined network context. */
 } TransportInterface_t;
 /* @[define_transportinterface] */

From e1af7cb5095627916091dbf154ab9d93eaffc534 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Tue, 23 Aug 2022 11:59:03 -0700
Subject: [PATCH 05/35] Update the publish method to use vectors

---
 source/core_mqtt.c                     | 242 ++++++++++++++-----------
 source/interface/transport_interface.h |  50 ++---
 2 files changed, 153 insertions(+), 139 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index e01b5f1b9..e1d8ec7c9 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -51,7 +51,7 @@
  *
  * @return Total number of bytes sent, or negative value on network error.
  */
-static int32_t sendPacket( MQTTContext_t * pContext,
+static int32_t sendBuffer( MQTTContext_t * pContext,
                            const uint8_t * pBufferToSend,
                            size_t bytesToSend );
 
@@ -600,14 +600,97 @@ static bool matchTopicFilter( const char * pTopicName,
 
 /*-----------------------------------------------------------*/
 
-static int32_t sendPacket( MQTTContext_t * pContext,
+static int32_t sendMessageVector( MQTTContext_t * pContext,
+                                  TransportOutVector_t * pIoVec,
+                                  size_t ioVecCount )
+{
+    uint32_t timeoutTime;
+    uint32_t bytesToSend = 0U;
+    int32_t bytesSentOrError = 0U;
+    TransportOutVector_t * pIoVectIterator;
+    size_t vectorsToBeSent = ioVecCount;
+
+    assert( pContext != NULL );
+    assert( pIoVec != NULL );
+    assert( pContext->getTime != NULL );
+    /* Send must alwaus be defined */
+    assert( pContext->transportInterface.send );
+
+    timeoutTime = pContext->getTime() + MQTT_SEND_RETRY_TIMEOUT_MS;
+
+    /* Count the total number of bytes to be sent as outlined in the vector. */
+    for( pIoVectIterator = pIoVec; pIoVectIterator < &( pIoVec[ ioVecCount ] ); pIoVectIterator++ )
+    {
+        bytesToSend += pIoVectIterator->iov_len;
+    }
+
+    /* Reset the iterator to point to the first entry in the array. */
+    pIoVectIterator = pIoVec;
+
+    while( ( pContext->getTime() < timeoutTime ) &&
+           ( bytesSentOrError < bytesToSend ) )
+    {
+        int32_t sendResult;
+        uint32_t bytesSentThisVector = 0U;
+
+        if( pContext->transportInterface.writev != NULL )
+        {
+            sendResult = pContext->transportInterface.writev( pContext->transportInterface.pNetworkContext,
+                                                              pIoVectIterator,
+                                                              vectorsToBeSent );
+        }
+        else
+        {
+            sendResult = sendBuffer( pContext,
+                                     pIoVectIterator->iov_base,
+                                     pIoVectIterator->iov_len,
+                                     ( timeoutTime - pContext->getTime() ) );
+        }
+
+        if( sendResult >= 0 )
+        {
+            bytesSentOrError += sendResult;
+            bytesSentThisVector += sendResult;
+        }
+        else
+        {
+            bytesSentOrError = sendResult;
+            break;
+        }
+
+        while( ( bytesSentThisVector >= pIoVectIterator->iov_len ) &&
+               ( pIoVectIterator < &( pIoVec[ ioVecCount ] ) ) )
+        {
+            bytesSentThisVector -= pIoVectIterator->iov_len;
+            pIoVectIterator++;
+
+            /* Update the number of vector which are yet to be sent. */
+            vectorsToBeSent--;
+        }
+
+        /* Some of the bytes from this vector were sent as well, update the length
+         * and the pointer to data in this vector. */
+        if( ( bytesSentThisVector > 0U ) &&
+            ( pIoVectIterator < &( pIoVec[ ioVecCount ] ) ) )
+        {
+            ( ( uint8_t * ) pIoVectIterator->iov_base ) += bytesSentThisVector;
+            pIoVectIterator->iov_len -= bytesSentThisVector;
+        }
+    }
+
+    return bytesSentOrError;
+}
+
+static int32_t sendBuffer( MQTTContext_t * pContext,
                            const uint8_t * pBufferToSend,
-                           size_t bytesToSend )
+                           size_t bytesToSend,
+                           uint32_t timeout )
 {
     const uint8_t * pIndex = pBufferToSend;
     size_t bytesRemaining = bytesToSend;
     int32_t totalBytesSent = 0, bytesSent;
     uint32_t lastSendTimeMs = 0U, timeSinceLastSendMs = 0U;
+    uint32_t timeoutTime;
     bool sendError = false;
 
     assert( pContext != NULL );
@@ -616,9 +699,7 @@ static int32_t sendPacket( MQTTContext_t * pContext,
     assert( pIndex != NULL );
 
     bytesRemaining = bytesToSend;
-
-    /* Record the most recent time of successful transmission. */
-    lastSendTimeMs = pContext->getTime();
+    timeoutTime = pContext->getTime() + timeout;
 
     /* Loop until the entire packet is sent. */
     while( ( bytesRemaining > 0UL ) && ( sendError == false ) )
@@ -970,9 +1051,10 @@ static MQTTStatus_t sendPublishAcks( MQTTContext_t * pContext,
 
         if( status == MQTTSuccess )
         {
-            bytesSent = sendPacket( pContext,
+            bytesSent = sendBuffer( pContext,
                                     pContext->networkBuffer.pBuffer,
-                                    MQTT_PUBLISH_ACK_PACKET_SIZE );
+                                    MQTT_PUBLISH_ACK_PACKET_SIZE,
+                                    MQTT_SEND_RETRY_TIMEOUT_MS );
         }
 
         if( bytesSent == ( int32_t ) MQTT_PUBLISH_ACK_PACKET_SIZE )
@@ -1425,109 +1507,52 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
                                             uint16_t packetId )
 {
     MQTTStatus_t status = MQTTSuccess;
-    int32_t bytesSent;
     uint8_t serializedPacketID[ 2 ];
-    const size_t packetIdLength = 2UL;
-    bool writeAndFlushAvailable;
+    TransportOutVector_t pIoVector[ 4 ];
+    size_t ioVectorLength;
+    size_t totalMessageLength;
+    const size_t packetIDLength = 2U;
 
-    writeAndFlushAvailable = ( ( pContext->transportInterface.write != NULL ) &&
-                             ( pContext->transportInterface.flush != NULL ) );
+    /* The header is sent first. */
+    pIoVector[ 0U ].iov_base = pMqttHeader;
+    pIoVector[ 0U ].iov_len = headerSize;
+    totalMessageLength = headerSize;
 
-    /* Encode the packet ID. */
-    serializedPacketID[ 0 ] = ( ( uint8_t ) ( ( packetId ) >> 8 ) );
-    serializedPacketID[ 1 ] = ( ( uint8_t ) ( ( packetId ) & 0x00ffU ) );
+    /* Then the topic name has to be sent. */
+    pIoVector[ 1U ].iov_base = pPublishInfo->pTopicName;
+    pIoVector[ 1U ].iov_len = pPublishInfo->topicNameLength;
+    totalMessageLength += pPublishInfo->topicNameLength;
 
-    /* Send the serialized publish packet header over network. */
-    if( writeAndFlushAvailable == true )
-    {
-        bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
-                                                        pMqttHeader,
-                                                        headerSize );
-    }
-    else
-    {
-        bytesSent = sendPacket( pContext,
-                                pMqttHeader,
-                                headerSize );
-    }
+    /* The next field's index should be 2 as the first two fields
+     * have been filled in. */
+    ioVectorLength = 2U;
 
-    if( bytesSent != ( int32_t ) headerSize )
-    {
-        status = MQTTSendFailed;
-    }
-    else
+    if( pPublishInfo->qos > MQTTQoS0 )
     {
-        /* Send the topic string over the network. */
-        if( writeAndFlushAvailable == true )
-        {
-            bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
-                                                            ( const uint8_t* )pPublishInfo->pTopicName,
-                                                            pPublishInfo->topicNameLength );
-        }
-        else
-        {
-            bytesSent = sendPacket( pContext,
-                                    ( const uint8_t * ) pPublishInfo->pTopicName,
-                                    pPublishInfo->topicNameLength );
-        }
+        /* Encode the packet ID. */
+        serializedPacketID[ 0 ] = ( ( uint8_t ) ( ( packetId ) >> 8 ) );
+        serializedPacketID[ 1 ] = ( ( uint8_t ) ( ( packetId ) & 0x00ffU ) );
 
-        if( bytesSent != ( ( int32_t ) pPublishInfo->topicNameLength ) )
-        {
-            status = MQTTSendFailed;
-        }
-    }
+        pIoVector[ ioVectorLength ].iov_base = serializedPacketID;
+        pIoVector[ ioVectorLength ].iov_len = packetIDLength;
 
-    if( ( status == MQTTSuccess ) && ( pPublishInfo->qos > MQTTQoS0 ) )
-    {
-        /* Send the packet ID over the network. */
-        if( writeAndFlushAvailable == true )
-        {
-            bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
-                                                            serializedPacketID,
-                                                            packetIdLength );
-        }
-        else
-        {
-            bytesSent = sendPacket( pContext,
-                                    serializedPacketID,
-                                    packetIdLength );
-        }
-
-        if( bytesSent != ( int32_t ) packetIdLength )
-        {
-            status = MQTTSendFailed;
-        }
+        ioVectorLength++;
+        totalMessageLength += packetIDLength;
     }
 
-    if( ( status == MQTTSuccess ) &&
-        ( pPublishInfo->payloadLength > 0U ) )
+    /* Publish packets are allowed to contain no payload. */
+    if( pPublishInfo->payloadLength > 0U )
     {
-        /* Send Payload if there is one to send. It is valid for a PUBLISH
-         * Packet to contain a zero length payload.*/
-        if( writeAndFlushAvailable == true )
-        {
-            bytesSent = pContext->transportInterface.write( pContext->transportInterface.pNetworkContext,
-                                                            pPublishInfo->pPayload,
-                                                            pPublishInfo->payloadLength );
-        }
-        else
-        {
-            bytesSent = sendPacket( pContext,
-                                    pPublishInfo->pPayload,
-                                    pPublishInfo->payloadLength );
-        }
+        pIoVector[ ioVectorLength ].iov_base = pPublishInfo->pPayload;;
+        pIoVector[ ioVectorLength ].iov_len = pPublishInfo->payloadLength;
 
-        if( bytesSent != ( ( int32_t ) pPublishInfo->payloadLength ) )
-        {
-            status = MQTTSendFailed;
-        }
+        ioVectorLength++;
+        totalMessageLength += pPublishInfo->payloadLength;
     }
 
-    if( ( status == MQTTSuccess ) &&
-        ( writeAndFlushAvailable == true ) )
+    if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalMessageLength )
     {
-        /* Flush the buffers to send the message over the network. */
-        ( void ) pContext->transportInterface.flush( pContext->transportInterface.pNetworkContext );
+        status = MQTTSendFailed;
     }
 
     return status;
@@ -1878,9 +1903,10 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
 
     if( status == MQTTSuccess )
     {
-        bytesSent = sendPacket( pContext,
+        bytesSent = sendBuffer( pContext,
                                 pContext->networkBuffer.pBuffer,
-                                packetSize );
+                                packetSize,
+                                MQTT_SEND_RETRY_TIMEOUT_MS );
 
         if( bytesSent < ( int32_t ) packetSize )
         {
@@ -1969,9 +1995,10 @@ MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
     if( status == MQTTSuccess )
     {
         /* Send serialized MQTT SUBSCRIBE packet to transport layer. */
-        bytesSent = sendPacket( pContext,
+        bytesSent = sendBuffer( pContext,
                                 pContext->networkBuffer.pBuffer,
-                                packetSize );
+                                packetSize,
+                                MQTT_SEND_RETRY_TIMEOUT_MS );
 
         if( bytesSent < ( int32_t ) packetSize )
         {
@@ -2118,9 +2145,10 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
     if( status == MQTTSuccess )
     {
         /* Send the serialized PINGREQ packet to transport layer. */
-        bytesSent = sendPacket( pContext,
+        bytesSent = sendBuffer( pContext,
                                 localBuffer.pBuffer,
-                                packetSize );
+                                MQTT_PACKET_PINGREQ_SIZE,
+                                MQTT_SEND_RETRY_TIMEOUT_MS );
 
         /* It is an error to not send the entire PINGREQ packet. */
         if( bytesSent < ( int32_t ) packetSize )
@@ -2181,9 +2209,10 @@ MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
     if( status == MQTTSuccess )
     {
         /* Send serialized MQTT UNSUBSCRIBE packet to transport layer. */
-        bytesSent = sendPacket( pContext,
+        bytesSent = sendBuffer( pContext,
                                 pContext->networkBuffer.pBuffer,
-                                packetSize );
+                                packetSize,
+                                MQTT_SEND_RETRY_TIMEOUT_MS );
 
         if( bytesSent < ( int32_t ) packetSize )
         {
@@ -2236,9 +2265,10 @@ MQTTStatus_t MQTT_Disconnect( MQTTContext_t * pContext )
 
     if( status == MQTTSuccess )
     {
-        bytesSent = sendPacket( pContext,
+        bytesSent = sendBuffer( pContext,
                                 localBuffer.pBuffer,
-                                packetSize );
+                                packetSize,
+                                MQTT_SEND_RETRY_TIMEOUT_MS );
 
         if( bytesSent < ( int32_t ) packetSize )
         {
diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index 3ad52f17a..a891c04a1 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -243,38 +243,21 @@ typedef int32_t ( * TransportSend_t )( NetworkContext_t * pNetworkContext,
                                        size_t bytesToSend );
 /* @[define_transportsend] */
 
-/**
- * @transportcallback
- * @brief Transport interface for writing data into the IP stack's buffers. This
- * data will not be sent immediately as the stack will wait for the application to
- * write more data.
- *
- * @param[in] pNetworkContext Implementation-defined network context.
- * @param[in] pBuffer Buffer containing the bytes to send over the network stack.
- * @param[in] bytesToWrite Number of bytes to write to the stack's buffers.
- *
- * @return The number of bytes written or a negative value to indicate error.
- *
- * @note If no data is written to the buffer due to the buffer being full this MUST
- * return zero as the return value.
- * A zero return value SHOULD represent that the send operation can be retried
- * by calling the API function. Zero MUST NOT be returned if a network disconnection
- * has occurred.
- */
-/* @[define_transportwrite] */
-typedef int32_t ( * TransportWrite_t )( NetworkContext_t * pNetworkContext,
-                                        const void * pBuffer,
-                                        size_t bytesToWrite );
-/* @[define_transportwrite] */
+typedef struct TransportOutVector
+{
+    const void * iov_base;      /* Base address of data */
+    size_t iov_len;             /* Length of data in buffer */
+} TransportOutVector_t;
 
 /**
  * @transportcallback
- * @brief Transport interface for sending all the data present in the IP-stacks buffers
- * added by the call to transport interface write function.
+ * @brief Transport interface function for "vectored" / scatter-gather based writes.
  *
  * @param[in] pNetworkContext Implementation-defined network context.
+ * @param[in] pIoVec An array of TransportIoVector_t structs.
+ * @param[in] ioVecCount Number of TransportIoVector_t in pIoVec.
  *
- * @return The number of bytes sent or a negative value to indicate error.
+ * @return The number of bytes written or a negative value to indicate error.
  *
  * @note If no data is written to the buffer due to the buffer being full this MUST
  * return zero as the return value.
@@ -282,9 +265,11 @@ typedef int32_t ( * TransportWrite_t )( NetworkContext_t * pNetworkContext,
  * by calling the API function. Zero MUST NOT be returned if a network disconnection
  * has occurred.
  */
-/* @[define_transportflush] */
-typedef int32_t ( * TransportFlush_t )( NetworkContext_t * pNetworkContext );
-/* @[define_transportflush] */
+/* @[define_transportwritev] */
+typedef int32_t ( * TransportWritev_t )( NetworkContext_t * pNetworkContext,
+                                         TransportOutVector_t * pIoVec,
+                                         size_t ioVecCount );
+/* @[define_transportwritev] */
 
 /**
  * @transportstruct
@@ -293,10 +278,9 @@ typedef int32_t ( * TransportFlush_t )( NetworkContext_t * pNetworkContext );
 /* @[define_transportinterface] */
 typedef struct TransportInterface
 {
-    TransportRecv_t recv;               /**< Transport receive interface. */
-    TransportSend_t send;               /**< Transport send interface. */
-    TransportWrite_t write;             /**< Transport write interface. */
-    TransportFlush_t flush;             /**< Transport flush interface. */
+    TransportRecv_t recv;               /**< Transport receive function pointer. */
+    TransportSend_t send;               /**< Transport send function pointer. */
+    TransportWritev_t writev;           /**< Transport writev function pointer. */
     NetworkContext_t * pNetworkContext; /**< Implementation-defined network context. */
 } TransportInterface_t;
 /* @[define_transportinterface] */

From d93e6effb376d06b03dda1a7af5b15a173ac3fa3 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Wed, 24 Aug 2022 15:21:18 -0700
Subject: [PATCH 06/35] Add vectored IO to all functions

---
 source/core_mqtt.c                    | 377 +++++++++++++++++++-------
 source/core_mqtt_serializer.c         | 135 +++++----
 source/include/core_mqtt.h            |   6 +-
 source/include/core_mqtt_serializer.h |  13 +
 4 files changed, 390 insertions(+), 141 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index e1d8ec7c9..d2b067d16 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -53,7 +53,13 @@
  */
 static int32_t sendBuffer( MQTTContext_t * pContext,
                            const uint8_t * pBufferToSend,
-                           size_t bytesToSend );
+                           size_t bytesToSend,
+                           uint32_t timeout );
+
+static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
+                                            const MQTTConnectInfo_t * pConnectInfo,
+                                            const MQTTPublishInfo_t * pWillInfo,
+                                            size_t remainingLength );
 
 /**
  * @brief Calculate the interval between two millisecond timestamps, including
@@ -1036,6 +1042,11 @@ static MQTTStatus_t sendPublishAcks( MQTTContext_t * pContext,
     int32_t bytesSent = 0;
     uint8_t packetTypeByte = 0U;
     MQTTPubAckType_t packetType;
+    MQTTFixedBuffer_t localBuffer;
+    uint8_t pubAckPacket[ MQTT_PUBLISH_ACK_PACKET_SIZE ];
+
+    localBuffer.pBuffer = pubAckPacket;
+    localBuffer.size = MQTT_PUBLISH_ACK_PACKET_SIZE;
 
     assert( pContext != NULL );
 
@@ -1045,14 +1056,16 @@ static MQTTStatus_t sendPublishAcks( MQTTContext_t * pContext,
     {
         packetType = getAckFromPacketType( packetTypeByte );
 
-        status = MQTT_SerializeAck( &( pContext->networkBuffer ),
+        status = MQTT_SerializeAck( &localBuffer,
                                     packetTypeByte,
                                     packetId );
 
         if( status == MQTTSuccess )
         {
+            /* Here, we are not using the vector approach for efficiency. There is just one buffer
+             * to be sent which can be achieved with a normal send call. */
             bytesSent = sendBuffer( pContext,
-                                    pContext->networkBuffer.pBuffer,
+                                    localBuffer.pBuffer,
                                     MQTT_PUBLISH_ACK_PACKET_SIZE,
                                     MQTT_SEND_RETRY_TIMEOUT_MS );
         }
@@ -1500,6 +1513,135 @@ static MQTTStatus_t validateSubscribeUnsubscribeParams( const MQTTContext_t * pC
 
 /*-----------------------------------------------------------*/
 
+static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
+                                                        uint8_t string,
+                                                        uint8_t length,
+                                                        TransportOutVector_t * iterator,
+                                                        size_t * updatedLength )
+{
+    size_t packetLength = 0U;
+    const size_t seralizedLengthFieldSize = 2U;
+
+    serailizedLength[ 0 ] = UINT16_HIGH_BYTE( length );
+    serailizedLength[ 1 ] = UINT16_LOW_BYTE( length );
+
+    iterator->iov_base = serailizedLength;
+    iterator->iov_len = seralizedLengthFieldSize;
+    iterator++;
+
+    iterator->iov_base = string;
+    iterator->iov_len = length;
+    iterator++;
+
+    packetLength = length + seralizedLengthFieldSize;
+
+    ( * updatedLength ) = (*updatedLength) + packetLength;
+
+    return iterator;
+}
+
+/*-----------------------------------------------------------*/
+
+static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
+                                              const MQTTSubscribeInfo_t * pSubscription,
+                                              uint16_t packetId,
+                                              size_t remainingLength )
+{
+    MQTTStatus_t status = MQTTSuccess;
+    uint8_t subscribeheader[ 5 ];
+    uint8_t * pIndex;
+    TransportOutVector_t pIoVector[ 4 ];
+    TransportOutVector_t* pIterator;
+    uint8_t serializedTopicFieldLength[ 2 ];
+    size_t totalPacketLength = 0U;
+    /* Subscribe packet always has 4 vector fields. Namely:
+     * Header + Topic Filter length + Topic filter + QoS */
+    const size_t ioVectorLength = 4U;
+
+    pIndex = subscribeheader;
+    pIterator = pIoVector;
+
+    pIndex = MQTT_SerializeSubscribeHeader( remainingLength,
+                                            pIndex,
+                                            packetId );
+
+    /* The header is to be sent first. */
+    pIterator->iov_base = subscribeheader;
+    pIterator->iov_len = ( size_t ) ( pIndex - subscribeheader );
+    pIterator++;
+    totalPacketLength += ( size_t ) ( pIndex - subscribeheader );
+
+    /* The topic filter gets sent next. */
+    pIterator = addEncodedStringToVector( serializedTopicFieldLength,
+                                          pSubscription->pTopicFilter,
+                                          pSubscription->topicFilterLength,
+                                          pIterator,
+                                          &totalPacketLength );
+
+    /* Lastly, the QoS gets sent. */
+    pIterator->iov_base = &( pSubscription->qos );
+    pIterator->iov_len = 1U;
+
+    if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
+    {
+        status = MQTTSendFailed;
+    }
+
+    return status;
+}
+
+/*-----------------------------------------------------------*/
+
+static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
+                                                const MQTTSubscribeInfo_t * pSubscription,
+                                                uint16_t packetId,
+                                                size_t remainingLength )
+{
+    MQTTStatus_t status = MQTTSuccess;
+    uint8_t unsubscribeheader[ 5 ];
+    uint8_t * pIndex;
+    TransportOutVector_t pIoVector[ 4 ];
+    TransportOutVector_t* pIterator;
+    uint8_t serializedTopicFieldLength[ 2 ];
+    size_t totalPacketLength = 0U;
+    /* Subscribe packet always has 4 vector fields. Namely:
+     * Header + Topic Filter length + Topic filter + QoS */
+    const size_t ioVectorLength = 4U;
+
+    pIndex = unsubscribeheader;
+    pIterator = pIoVector;
+
+    pIndex = MQTT_SerializeUnsubscribeHeader( remainingLength,
+                                              pIndex,
+                                              packetId );
+
+    /* The header is to be sent first. */
+    pIterator->iov_base = unsubscribeheader;
+    pIterator->iov_len = ( size_t ) ( pIndex - unsubscribeheader );
+    pIterator++;
+    totalPacketLength += ( size_t ) ( pIndex - unsubscribeheader );
+
+    /* The topic filter gets sent next. */
+    pIterator = addEncodedStringToVector( serializedTopicFieldLength,
+                                          pSubscription->pTopicFilter,
+                                          pSubscription->topicFilterLength,
+                                          pIterator,
+                                          &totalPacketLength );
+
+    /* Lastly, the QoS gets sent. */
+    pIterator->iov_base = &( pSubscription->qos );
+    pIterator->iov_len = 1U;
+
+    if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
+    {
+        status = MQTTSendFailed;
+    }
+
+    return status;
+}
+
+/*-----------------------------------------------------------*/
+
 static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
                                             const MQTTPublishInfo_t * pPublishInfo,
                                             const uint8_t * pMqttHeader,
@@ -1560,6 +1702,117 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
 
 /*-----------------------------------------------------------*/
 
+static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
+                                            const MQTTConnectInfo_t * pConnectInfo,
+                                            const MQTTPublishInfo_t * pWillInfo,
+                                            size_t remainingLength )
+{
+    MQTTStatus_t status = MQTTSuccess;
+    size_t connectPacketSize = 0;
+    TransportOutVector_t* iterator;
+    size_t ioVectorLength = 0U;
+    size_t totalMessageLength = 0U;
+
+    /* Connect packet header can be of maximum 15 bytes. */
+    uint8_t connectPacketHeader[ 15 ];
+    uint8_t* pIndex = connectPacketHeader;
+    TransportOutVector_t pIoVector[ 11 ];
+    uint8_t serializedClientIDLength[ 2 ];
+    uint8_t serializedTopicLength[ 2 ];
+    uint8_t serializedPayloadLength[ 2 ];
+    uint8_t serializedUsernameLength[ 2 ];
+    uint8_t serializedPasswordLength[ 2 ];
+
+    iterator = pIoVector;
+
+    /* Validate arguments. */
+    if( pConnectInfo == NULL )
+    {
+        LogError( ( "Argument cannot be NULL: pConnectInfo=%p, "
+                    "pFixedBuffer=%p.",
+                    ( void * ) pConnectInfo ) );
+        status = MQTTBadParameter;
+    }
+    else if( ( pWillInfo != NULL ) && ( pWillInfo->pTopicName == NULL ) )
+    {
+        LogError( ( "pWillInfo->pTopicName cannot be NULL if Will is present." ) );
+        status = MQTTBadParameter;
+    }
+    else
+    {
+        pIndex = MQTT_SerializeConnectFixedHeader( pIndex,
+                                                   pConnectInfo,
+                                                   pWillInfo,
+                                                   remainingLength );
+
+        assert( ( pIndex - connectPacketHeader ) <= 15 );
+
+        /* The header gets sent first. */
+        iterator->iov_base = connectPacketHeader;
+        iterator->iov_len = ( size_t ) ( pIndex - connectPacketHeader );
+        totalMessageLength += iterator->iov_len; 
+        iterator++;
+        
+
+        /* Serialize the client ID. */
+        iterator = addEncodedStringToVector( serializedClientIDLength,
+                                             pConnectInfo->pClientIdentifier,
+                                             pConnectInfo->clientIdentifierLength,
+                                             iterator,
+                                             &totalMessageLength );
+
+        if( pWillInfo != NULL )
+        {
+            /* Serialize the topic. */
+            iterator = addEncodedStringToVector( serializedTopicLength,
+                                                 pWillInfo->pTopicName,
+                                                 pWillInfo->topicNameLength,
+                                                 iterator,
+                                                 &totalMessageLength );
+
+            /* Serialize the payload. */
+            iterator = addEncodedStringToVector( serializedPayloadLength,
+                                                 pWillInfo->pPayload,
+                                                 pWillInfo->payloadLength,
+                                                 iterator,
+                                                 &totalMessageLength );
+        }
+
+        /* Encode the user name if provided. */
+        if( pConnectInfo->pUserName != NULL )
+        {
+            /* Serialize the user name string. */
+            iterator = addEncodedStringToVector( serializedUsernameLength,
+                                                 pConnectInfo->pUserName,
+                                                 pConnectInfo->userNameLength,
+                                                 iterator,
+                                                 &totalMessageLength );
+        }
+
+        /* Encode the password if provided. */
+        if( pConnectInfo->pPassword != NULL )
+        {
+            /* Serialize the user name string. */
+            iterator = addEncodedStringToVector( serializedPasswordLength,
+                                                 pConnectInfo->pPassword,
+                                                 pConnectInfo->passwordLength,
+                                                 iterator,
+                                                 &totalMessageLength );
+        }
+
+        ioVectorLength = ( size_t ) ( ( iterator - pIoVector ) + 1 );
+
+        if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalMessageLength )
+        {
+            status = MQTTSendFailed;
+        }
+    }
+
+    return status;
+}
+
+/*-----------------------------------------------------------*/
+
 static MQTTStatus_t receiveConnack( const MQTTContext_t * pContext,
                                     uint32_t timeoutMs,
                                     bool cleanSession,
@@ -1895,29 +2148,10 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
 
     if( status == MQTTSuccess )
     {
-        status = MQTT_SerializeConnect( pConnectInfo,
-                                        pWillInfo,
-                                        remainingLength,
-                                        &( pContext->networkBuffer ) );
-    }
-
-    if( status == MQTTSuccess )
-    {
-        bytesSent = sendBuffer( pContext,
-                                pContext->networkBuffer.pBuffer,
-                                packetSize,
-                                MQTT_SEND_RETRY_TIMEOUT_MS );
-
-        if( bytesSent < ( int32_t ) packetSize )
-        {
-            LogError( ( "Transport send failed for CONNECT packet." ) );
-            status = MQTTSendFailed;
-        }
-        else
-        {
-            LogDebug( ( "Sent %ld bytes of CONNECT packet.",
-                        ( long int ) bytesSent ) );
-        }
+        status = sendConnectWithoutCopy( pContext,
+                                         pConnectInfo,
+                                         pWillInfo,
+                                         remainingLength );
     }
 
     /* Read CONNACK from transport layer. */
@@ -1957,8 +2191,7 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
 /*-----------------------------------------------------------*/
 
 MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
-                             const MQTTSubscribeInfo_t * pSubscriptionList,
-                             size_t subscriptionCount,
+                             const MQTTSubscribeInfo_t * pSubscription,
                              uint16_t packetId )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
@@ -1966,15 +2199,15 @@ MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
 
     /* Validate arguments. */
     MQTTStatus_t status = validateSubscribeUnsubscribeParams( pContext,
-                                                              pSubscriptionList,
-                                                              subscriptionCount,
+                                                              pSubscription,
+                                                              1U,
                                                               packetId );
 
     if( status == MQTTSuccess )
     {
         /* Get the remaining length and packet size.*/
-        status = MQTT_GetSubscribePacketSize( pSubscriptionList,
-                                              subscriptionCount,
+        status = MQTT_GetSubscribePacketSize( pSubscription,
+                                              1U,
                                               &remainingLength,
                                               &packetSize );
         LogDebug( ( "SUBSCRIBE packet size is %lu and remaining length is %lu.",
@@ -1984,32 +2217,11 @@ MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
 
     if( status == MQTTSuccess )
     {
-        /* Serialize MQTT SUBSCRIBE packet. */
-        status = MQTT_SerializeSubscribe( pSubscriptionList,
-                                          subscriptionCount,
-                                          packetId,
-                                          remainingLength,
-                                          &( pContext->networkBuffer ) );
-    }
-
-    if( status == MQTTSuccess )
-    {
-        /* Send serialized MQTT SUBSCRIBE packet to transport layer. */
-        bytesSent = sendBuffer( pContext,
-                                pContext->networkBuffer.pBuffer,
-                                packetSize,
-                                MQTT_SEND_RETRY_TIMEOUT_MS );
-
-        if( bytesSent < ( int32_t ) packetSize )
-        {
-            LogError( ( "Transport send failed for SUBSCRIBE packet." ) );
-            status = MQTTSendFailed;
-        }
-        else
-        {
-            LogDebug( ( "Sent %ld bytes of SUBSCRIBE packet.",
-                        ( long int ) bytesSent ) );
-        }
+        /* Send MQTT SUBSCRIBE packet. */
+        status = sendSubscribeWithoutCopy( pContext,
+                                           pSubscription,
+                                           packetId,
+                                           remainingLength );
     }
 
     return status;
@@ -2144,7 +2356,10 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
 
     if( status == MQTTSuccess )
     {
-        /* Send the serialized PINGREQ packet to transport layer. */
+        /* Send the serialized PINGREQ packet to transport layer.
+         * Here, we do not use the vectored IO approach for efficiency as the
+         * Ping packet does not have numerous fields which need to be copied
+         * from the user provided buffers. Thus it can be sent directly. */
         bytesSent = sendBuffer( pContext,
                                 localBuffer.pBuffer,
                                 MQTT_PACKET_PINGREQ_SIZE,
@@ -2171,8 +2386,7 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
 /*-----------------------------------------------------------*/
 
 MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
-                               const MQTTSubscribeInfo_t * pSubscriptionList,
-                               size_t subscriptionCount,
+                               const MQTTSubscribeInfo_t * pSubscription,
                                uint16_t packetId )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
@@ -2180,15 +2394,15 @@ MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
 
     /* Validate arguments. */
     MQTTStatus_t status = validateSubscribeUnsubscribeParams( pContext,
-                                                              pSubscriptionList,
-                                                              subscriptionCount,
+                                                              pSubscription,
+                                                              1U,
                                                               packetId );
 
     if( status == MQTTSuccess )
     {
         /* Get the remaining length and packet size.*/
-        status = MQTT_GetUnsubscribePacketSize( pSubscriptionList,
-                                                subscriptionCount,
+        status = MQTT_GetUnsubscribePacketSize( pSubscription,
+                                                1U,
                                                 &remainingLength,
                                                 &packetSize );
         LogDebug( ( "UNSUBSCRIBE packet size is %lu and remaining length is %lu.",
@@ -2198,32 +2412,10 @@ MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
 
     if( status == MQTTSuccess )
     {
-        /* Serialize MQTT UNSUBSCRIBE packet. */
-        status = MQTT_SerializeUnsubscribe( pSubscriptionList,
-                                            subscriptionCount,
-                                            packetId,
-                                            remainingLength,
-                                            &( pContext->networkBuffer ) );
-    }
-
-    if( status == MQTTSuccess )
-    {
-        /* Send serialized MQTT UNSUBSCRIBE packet to transport layer. */
-        bytesSent = sendBuffer( pContext,
-                                pContext->networkBuffer.pBuffer,
-                                packetSize,
-                                MQTT_SEND_RETRY_TIMEOUT_MS );
-
-        if( bytesSent < ( int32_t ) packetSize )
-        {
-            LogError( ( "Transport send failed for UNSUBSCRIBE packet." ) );
-            status = MQTTSendFailed;
-        }
-        else
-        {
-            LogDebug( ( "Sent %ld bytes of UNSUBSCRIBE packet.",
-                        ( long int ) bytesSent ) );
-        }
+        status = sendUnsubscribeWithoutCopy( pContext,
+                                             pSubscription,
+                                             packetId,
+                                             remainingLength );
     }
 
     return status;
@@ -2265,6 +2457,9 @@ MQTTStatus_t MQTT_Disconnect( MQTTContext_t * pContext )
 
     if( status == MQTTSuccess )
     {
+        /* Here we do not use vectors as the disconnect packet has fixed fields
+         * which do not reside in user provided buffers. Thus, it can be sent
+         * using a simple send call. */
         bytesSent = sendBuffer( pContext,
                                 localBuffer.pBuffer,
                                 packetSize,
diff --git a/source/core_mqtt_serializer.c b/source/core_mqtt_serializer.c
index f228460bd..09b620d70 100644
--- a/source/core_mqtt_serializer.c
+++ b/source/core_mqtt_serializer.c
@@ -1352,37 +1352,30 @@ static MQTTStatus_t deserializePingresp( const MQTTPacketInfo_t * pPingresp )
     return status;
 }
 
-/*-----------------------------------------------------------*/
-
-static void serializeConnectPacket( const MQTTConnectInfo_t * pConnectInfo,
-                                    const MQTTPublishInfo_t * pWillInfo,
-                                    size_t remainingLength,
-                                    const MQTTFixedBuffer_t * pFixedBuffer )
+uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
+                                            const MQTTConnectInfo_t * pConnectInfo,
+                                            const MQTTPublishInfo_t * pWillInfo,
+                                            size_t remainingLength )
 {
+    uint8_t * pIndexLocal = pIndex;
     uint8_t connectFlags = 0U;
-    uint8_t * pIndex = NULL;
-
-    assert( pConnectInfo != NULL );
-    assert( pFixedBuffer != NULL );
-    assert( pFixedBuffer->pBuffer != NULL );
-
-    pIndex = pFixedBuffer->pBuffer;
+    
     /* The first byte in the CONNECT packet is the control packet type. */
-    *pIndex = MQTT_PACKET_TYPE_CONNECT;
-    pIndex++;
+    *pIndexLocal = MQTT_PACKET_TYPE_CONNECT;
+    pIndexLocal++;
 
     /* The remaining length of the CONNECT packet is encoded starting from the
      * second byte. The remaining length does not include the length of the fixed
      * header or the encoding of the remaining length. */
-    pIndex = encodeRemainingLength( pIndex, remainingLength );
+    pIndexLocal = encodeRemainingLength( pIndex, remainingLength );
 
     /* The string "MQTT" is placed at the beginning of the CONNECT packet's variable
      * header. This string is 4 bytes long. */
-    pIndex = encodeString( pIndex, "MQTT", 4 );
+    pIndexLocal = encodeString( pIndex, "MQTT", 4 );
 
     /* The MQTT protocol version is the second field of the variable header. */
-    *pIndex = MQTT_VERSION_3_1_1;
-    pIndex++;
+    *pIndexLocal = MQTT_VERSION_3_1_1;
+    pIndexLocal++;
 
     /* Set the clean session flag if needed. */
     if( pConnectInfo->cleanSession == true )
@@ -1426,13 +1419,37 @@ static void serializeConnectPacket( const MQTTConnectInfo_t * pConnectInfo,
         }
     }
 
-    *pIndex = connectFlags;
-    pIndex++;
+    *pIndexLocal = connectFlags;
+    pIndexLocal++;
 
     /* Write the 2 bytes of the keep alive interval into the CONNECT packet. */
-    *pIndex = UINT16_HIGH_BYTE( pConnectInfo->keepAliveSeconds );
-    *( pIndex + 1 ) = UINT16_LOW_BYTE( pConnectInfo->keepAliveSeconds );
-    pIndex += 2;
+    *pIndexLocal = UINT16_HIGH_BYTE( pConnectInfo->keepAliveSeconds );
+    *( pIndexLocal + 1 ) = UINT16_LOW_BYTE( pConnectInfo->keepAliveSeconds );
+    pIndexLocal += 2;
+
+    return pIndexLocal;
+}
+/*-----------------------------------------------------------*/
+
+static void serializeConnectPacket( const MQTTConnectInfo_t * pConnectInfo,
+                                    const MQTTPublishInfo_t * pWillInfo,
+                                    size_t remainingLength,
+                                    const MQTTFixedBuffer_t * pFixedBuffer )
+{
+    uint8_t connectFlags = 0U;
+    uint8_t * pIndex = NULL;
+
+    assert( pConnectInfo != NULL );
+    assert( pFixedBuffer != NULL );
+    assert( pFixedBuffer->pBuffer != NULL );
+
+    pIndex = pFixedBuffer->pBuffer;
+    
+    /* Serialize the header. */
+    pIndex = MQTT_SerializeConnectFixedHeader( pIndex,
+                                               pConnectInfo,
+                                               pWillInfo,
+                                               remainingLength );
 
     /* Write the client identifier into the CONNECT packet. */
     pIndex = encodeString( pIndex,
@@ -1669,6 +1686,50 @@ MQTTStatus_t MQTT_GetSubscribePacketSize( const MQTTSubscribeInfo_t * pSubscript
 
 /*-----------------------------------------------------------*/
 
+uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength,
+                                         uint8_t * pIndex,
+                                         uint16_t packetId )
+{
+    uint8_t * pIterator = pIndex;
+
+    /* The first byte in SUBSCRIBE is the packet type. */
+    *pIterator = MQTT_PACKET_TYPE_SUBSCRIBE;
+    pIterator++;
+
+    /* Encode the "Remaining length" starting from the second byte. */
+    pIterator = encodeRemainingLength( pIterator, remainingLength );
+
+    /* Place the packet identifier into the SUBSCRIBE packet. */
+    *pIterator = UINT16_HIGH_BYTE( packetId );
+    *( pIterator + 1 ) = UINT16_LOW_BYTE( packetId );
+    pIterator += 2;
+
+    return pIterator;
+}
+
+/*-----------------------------------------------------------*/
+
+uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength,
+                                           uint8_t * pIndex,
+                                           uint16_t packetId )
+{
+    uint8_t * pIterator = pIndex;
+
+    /* The first byte in UNSUBSCRIBE is the packet type. */
+    *pIterator = MQTT_PACKET_TYPE_UNSUBSCRIBE;
+    pIterator++;
+
+    /* Encode the "Remaining length" starting from the second byte. */
+    pIterator = encodeRemainingLength( pIterator, remainingLength );
+
+    /* Place the packet identifier into the SUBSCRIBE packet. */
+    *pIterator = UINT16_HIGH_BYTE( packetId );
+    *( pIterator + 1 ) = UINT16_LOW_BYTE( packetId );
+    pIterator += 2;
+
+    return pIterator;
+}
+
 MQTTStatus_t MQTT_SerializeSubscribe( const MQTTSubscribeInfo_t * pSubscriptionList,
                                       size_t subscriptionCount,
                                       uint16_t packetId,
@@ -1690,17 +1751,9 @@ MQTTStatus_t MQTT_SerializeSubscribe( const MQTTSubscribeInfo_t * pSubscriptionL
     {
         pIndex = pFixedBuffer->pBuffer;
 
-        /* The first byte in SUBSCRIBE is the packet type. */
-        *pIndex = MQTT_PACKET_TYPE_SUBSCRIBE;
-        pIndex++;
-
-        /* Encode the "Remaining length" starting from the second byte. */
-        pIndex = encodeRemainingLength( pIndex, remainingLength );
-
-        /* Place the packet identifier into the SUBSCRIBE packet. */
-        *pIndex = UINT16_HIGH_BYTE( packetId );
-        *( pIndex + 1 ) = UINT16_LOW_BYTE( packetId );
-        pIndex += 2;
+        pIndex = MQTT_SerializeSubscribeHeader( remainingLength,
+                                                pIndex,
+                                                packetId );
 
         /* Serialize each subscription topic filter and QoS. */
         for( i = 0; i < subscriptionCount; i++ )
@@ -1783,17 +1836,7 @@ MQTTStatus_t MQTT_SerializeUnsubscribe( const MQTTSubscribeInfo_t * pSubscriptio
         /* Get the start of the buffer to the iterator variable. */
         pIndex = pFixedBuffer->pBuffer;
 
-        /* The first byte in UNSUBSCRIBE is the packet type. */
-        *pIndex = MQTT_PACKET_TYPE_UNSUBSCRIBE;
-        pIndex++;
-
-        /* Encode the "Remaining length" starting from the second byte. */
-        pIndex = encodeRemainingLength( pIndex, remainingLength );
-
-        /* Place the packet identifier into the UNSUBSCRIBE packet. */
-        *pIndex = UINT16_HIGH_BYTE( packetId );
-        *( pIndex + 1 ) = UINT16_LOW_BYTE( packetId );
-        pIndex += 2;
+        pIndex = MQTT_SerializeUnsubscribeHeader( remainingLength, pIndex, packetId );
 
         /* Serialize each subscription topic filter. */
         for( i = 0; i < subscriptionCount; i++ )
diff --git a/source/include/core_mqtt.h b/source/include/core_mqtt.h
index 4feca99c5..361e3cf36 100644
--- a/source/include/core_mqtt.h
+++ b/source/include/core_mqtt.h
@@ -475,8 +475,7 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
  */
 /* @[declare_mqtt_subscribe] */
 MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
-                             const MQTTSubscribeInfo_t * pSubscriptionList,
-                             size_t subscriptionCount,
+                             const MQTTSubscribeInfo_t * pSubscription,
                              uint16_t packetId );
 /* @[declare_mqtt_subscribe] */
 
@@ -591,8 +590,7 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
  */
 /* @[declare_mqtt_unsubscribe] */
 MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
-                               const MQTTSubscribeInfo_t * pSubscriptionList,
-                               size_t subscriptionCount,
+                               const MQTTSubscribeInfo_t * pSubscription,
                                uint16_t packetId );
 /* @[declare_mqtt_unsubscribe] */
 
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index c6088e37e..644f30c7d 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -1315,6 +1315,19 @@ MQTTStatus_t MQTT_GetIncomingPacketTypeAndLength( TransportRecv_t readFunc,
                                                   MQTTPacketInfo_t * pIncomingPacket );
 /* @[declare_mqtt_getincomingpackettypeandlength] */
 
+uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
+                                            const MQTTConnectInfo_t * pConnectInfo,
+                                            const MQTTPublishInfo_t * pWillInfo,
+                                            size_t remainingLength );
+
+uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength,
+                                         uint8_t * pIndex,
+                                         uint16_t packetId );
+
+uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength,
+                                           uint8_t * pIndex,
+                                           uint16_t packetId );
+
 /* *INDENT-OFF* */
 #ifdef __cplusplus
     }

From d01829b472370994eb44bdfe9274187c0128bdd4 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Wed, 24 Aug 2022 22:54:42 +0000
Subject: [PATCH 07/35] Fix formatting

---
 source/core_mqtt.c            | 20 ++++++++++++--------
 source/core_mqtt_serializer.c |  4 ++--
 2 files changed, 14 insertions(+), 10 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index d2b067d16..3b8bda0b3 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -292,6 +292,7 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
                                             const uint8_t * pMqttHeader,
                                             size_t headerSize,
                                             uint16_t packetId );
+
 /**
  * @brief Serializes a PUBLISH message.
  *
@@ -1535,7 +1536,7 @@ static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength
 
     packetLength = length + seralizedLengthFieldSize;
 
-    ( * updatedLength ) = (*updatedLength) + packetLength;
+    ( *updatedLength ) = ( *updatedLength ) + packetLength;
 
     return iterator;
 }
@@ -1551,9 +1552,10 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
     uint8_t subscribeheader[ 5 ];
     uint8_t * pIndex;
     TransportOutVector_t pIoVector[ 4 ];
-    TransportOutVector_t* pIterator;
+    TransportOutVector_t * pIterator;
     uint8_t serializedTopicFieldLength[ 2 ];
     size_t totalPacketLength = 0U;
+
     /* Subscribe packet always has 4 vector fields. Namely:
      * Header + Topic Filter length + Topic filter + QoS */
     const size_t ioVectorLength = 4U;
@@ -1601,9 +1603,10 @@ static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
     uint8_t unsubscribeheader[ 5 ];
     uint8_t * pIndex;
     TransportOutVector_t pIoVector[ 4 ];
-    TransportOutVector_t* pIterator;
+    TransportOutVector_t * pIterator;
     uint8_t serializedTopicFieldLength[ 2 ];
     size_t totalPacketLength = 0U;
+
     /* Subscribe packet always has 4 vector fields. Namely:
      * Header + Topic Filter length + Topic filter + QoS */
     const size_t ioVectorLength = 4U;
@@ -1685,7 +1688,7 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
     /* Publish packets are allowed to contain no payload. */
     if( pPublishInfo->payloadLength > 0U )
     {
-        pIoVector[ ioVectorLength ].iov_base = pPublishInfo->pPayload;;
+        pIoVector[ ioVectorLength ].iov_base = pPublishInfo->pPayload;
         pIoVector[ ioVectorLength ].iov_len = pPublishInfo->payloadLength;
 
         ioVectorLength++;
@@ -1709,13 +1712,13 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
 {
     MQTTStatus_t status = MQTTSuccess;
     size_t connectPacketSize = 0;
-    TransportOutVector_t* iterator;
+    TransportOutVector_t * iterator;
     size_t ioVectorLength = 0U;
     size_t totalMessageLength = 0U;
 
     /* Connect packet header can be of maximum 15 bytes. */
     uint8_t connectPacketHeader[ 15 ];
-    uint8_t* pIndex = connectPacketHeader;
+    uint8_t * pIndex = connectPacketHeader;
     TransportOutVector_t pIoVector[ 11 ];
     uint8_t serializedClientIDLength[ 2 ];
     uint8_t serializedTopicLength[ 2 ];
@@ -1750,9 +1753,9 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
         /* The header gets sent first. */
         iterator->iov_base = connectPacketHeader;
         iterator->iov_len = ( size_t ) ( pIndex - connectPacketHeader );
-        totalMessageLength += iterator->iov_len; 
+        totalMessageLength += iterator->iov_len;
         iterator++;
-        
+
 
         /* Serialize the client ID. */
         iterator = addEncodedStringToVector( serializedClientIDLength,
@@ -2235,6 +2238,7 @@ MQTTStatus_t MQTT_Publish( MQTTContext_t * pContext,
 {
     size_t headerSize = 0UL, remainingLength = 0UL, packetSize = 0UL;
     MQTTPublishState_t publishStatus = MQTTStateNull;
+
     /* 1 header byte + 4 bytes (maximum) required for encoding the length +
      * 2 bytes for topic string. */
     uint8_t mqttHeader[ 7 ];
diff --git a/source/core_mqtt_serializer.c b/source/core_mqtt_serializer.c
index 09b620d70..f132069dd 100644
--- a/source/core_mqtt_serializer.c
+++ b/source/core_mqtt_serializer.c
@@ -1359,7 +1359,7 @@ uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
 {
     uint8_t * pIndexLocal = pIndex;
     uint8_t connectFlags = 0U;
-    
+
     /* The first byte in the CONNECT packet is the control packet type. */
     *pIndexLocal = MQTT_PACKET_TYPE_CONNECT;
     pIndexLocal++;
@@ -1444,7 +1444,7 @@ static void serializeConnectPacket( const MQTTConnectInfo_t * pConnectInfo,
     assert( pFixedBuffer->pBuffer != NULL );
 
     pIndex = pFixedBuffer->pBuffer;
-    
+
     /* Serialize the header. */
     pIndex = MQTT_SerializeConnectFixedHeader( pIndex,
                                                pConnectInfo,

From f3812f2b11a1595c23eac06abd4f0a107b4a913a Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Wed, 24 Aug 2022 23:14:09 +0000
Subject: [PATCH 08/35] Reduce complexity score

---
 source/core_mqtt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 3b8bda0b3..5040c6d66 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -1715,6 +1715,7 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
     TransportOutVector_t * iterator;
     size_t ioVectorLength = 0U;
     size_t totalMessageLength = 0U;
+    int32_t bytesSentOrError;
 
     /* Connect packet header can be of maximum 15 bytes. */
     uint8_t connectPacketHeader[ 15 ];
@@ -1805,7 +1806,9 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
 
         ioVectorLength = ( size_t ) ( ( iterator - pIoVector ) + 1 );
 
-        if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalMessageLength )
+        bytesSentOrError = sendMessageVector( pContext, pIoVector, ioVectorLength );
+
+        if( bytesSentOrError != ( int32_t ) totalMessageLength )
         {
             status = MQTTSendFailed;
         }

From 78623b84734a4b43a572e63551327b378624179f Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Wed, 24 Aug 2022 23:58:26 +0000
Subject: [PATCH 09/35] Fix spell check and complexity score

---
 lexicon.txt                            |   5 ++
 source/core_mqtt.c                     | 100 +++++++++++++++----------
 source/interface/transport_interface.h |   4 +-
 3 files changed, 67 insertions(+), 42 deletions(-)

diff --git a/lexicon.txt b/lexicon.txt
index f3e782b6b..818ba164c 100644
--- a/lexicon.txt
+++ b/lexicon.txt
@@ -112,7 +112,9 @@ initializeconnectinfo
 initializesubscribeinfo
 initializewillinfo
 int
+io
 iot
+ioveccount
 isn
 iso
 keepaliveintervalsec
@@ -238,11 +240,13 @@ pingreqs
 pingreqsendtimems
 pingresp
 pingresps
+piovec
 pismatch
 plaintext
 pmatch
 pmessage
 pmqttcontext
+pmqttheader
 pnameindex
 pnetworkbuffer
 pnetworkcontext
@@ -400,6 +404,7 @@ validatesubscribeunsubscribeparams
 validator
 waitingforpingresp
 willinfo
+writev
 xa
 xb
 xc
diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 5040c6d66..84f82a824 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -620,7 +620,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
     assert( pContext != NULL );
     assert( pIoVec != NULL );
     assert( pContext->getTime != NULL );
-    /* Send must alwaus be defined */
+    /* Send must always be defined */
     assert( pContext->transportInterface.send );
 
     timeoutTime = pContext->getTime() + MQTT_SEND_RETRY_TIMEOUT_MS;
@@ -1705,6 +1705,57 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
 
 /*-----------------------------------------------------------*/
 
+static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
+                                   const MQTTPublishInfo_t * pWillInfo,
+                                   size_t * totalMessageLength,
+                                   TransportOutVector_t * iterator,
+                                   uint8_t serializedTopicLength[ 2 ],
+                                   uint8_t serializedPayloadLength[ 2 ],
+                                   uint8_t serializedUsernameLength[ 2 ],
+                                   uint8_t serializedPasswordLength[ 2 ] )
+{
+    if( pWillInfo != NULL )
+    {
+        /* Serialize the topic. */
+        iterator = addEncodedStringToVector( serializedTopicLength,
+                                             pWillInfo->pTopicName,
+                                             pWillInfo->topicNameLength,
+                                             iterator,
+                                             &totalMessageLength );
+
+        /* Serialize the payload. */
+        iterator = addEncodedStringToVector( serializedPayloadLength,
+                                             pWillInfo->pPayload,
+                                             pWillInfo->payloadLength,
+                                             iterator,
+                                             &totalMessageLength );
+    }
+
+    /* Encode the user name if provided. */
+    if( pConnectInfo->pUserName != NULL )
+    {
+        /* Serialize the user name string. */
+        iterator = addEncodedStringToVector( serializedUsernameLength,
+                                             pConnectInfo->pUserName,
+                                             pConnectInfo->userNameLength,
+                                             iterator,
+                                             &totalMessageLength );
+    }
+
+    /* Encode the password if provided. */
+    if( pConnectInfo->pPassword != NULL )
+    {
+        /* Serialize the user name string. */
+        iterator = addEncodedStringToVector( serializedPasswordLength,
+                                             pConnectInfo->pPassword,
+                                             pConnectInfo->passwordLength,
+                                             iterator,
+                                             &totalMessageLength );
+    }
+}
+
+/*-----------------------------------------------------------*/
+
 static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                             const MQTTConnectInfo_t * pConnectInfo,
                                             const MQTTPublishInfo_t * pWillInfo,
@@ -1757,7 +1808,6 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
         totalMessageLength += iterator->iov_len;
         iterator++;
 
-
         /* Serialize the client ID. */
         iterator = addEncodedStringToVector( serializedClientIDLength,
                                              pConnectInfo->pClientIdentifier,
@@ -1765,44 +1815,14 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                              iterator,
                                              &totalMessageLength );
 
-        if( pWillInfo != NULL )
-        {
-            /* Serialize the topic. */
-            iterator = addEncodedStringToVector( serializedTopicLength,
-                                                 pWillInfo->pTopicName,
-                                                 pWillInfo->topicNameLength,
-                                                 iterator,
-                                                 &totalMessageLength );
-
-            /* Serialize the payload. */
-            iterator = addEncodedStringToVector( serializedPayloadLength,
-                                                 pWillInfo->pPayload,
-                                                 pWillInfo->payloadLength,
-                                                 iterator,
-                                                 &totalMessageLength );
-        }
-
-        /* Encode the user name if provided. */
-        if( pConnectInfo->pUserName != NULL )
-        {
-            /* Serialize the user name string. */
-            iterator = addEncodedStringToVector( serializedUsernameLength,
-                                                 pConnectInfo->pUserName,
-                                                 pConnectInfo->userNameLength,
-                                                 iterator,
-                                                 &totalMessageLength );
-        }
-
-        /* Encode the password if provided. */
-        if( pConnectInfo->pPassword != NULL )
-        {
-            /* Serialize the user name string. */
-            iterator = addEncodedStringToVector( serializedPasswordLength,
-                                                 pConnectInfo->pPassword,
-                                                 pConnectInfo->passwordLength,
-                                                 iterator,
-                                                 &totalMessageLength );
-        }
+        addWillAndConnectInfo( pWillInfo,
+                               pConnectInfo,
+                               &totalMessageLength,
+                               iterator,
+                               serializedTopicLength,
+                               serializedPayloadLength,
+                               serializedUsernameLength,
+                               serializedPasswordLength );
 
         ioVectorLength = ( size_t ) ( ( iterator - pIoVector ) + 1 );
 
diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index a891c04a1..c7b6de6df 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -245,8 +245,8 @@ typedef int32_t ( * TransportSend_t )( NetworkContext_t * pNetworkContext,
 
 typedef struct TransportOutVector
 {
-    const void * iov_base;      /* Base address of data */
-    size_t iov_len;             /* Length of data in buffer */
+    const void * iov_base; /* Base address of data */
+    size_t iov_len;        /* Length of data in buffer */
 } TransportOutVector_t;
 
 /**

From 92886c58f4ae9f41c78a75199bc80cd94338fb62 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 00:02:55 +0000
Subject: [PATCH 10/35] Fix breaking build

---
 source/core_mqtt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 84f82a824..9a2b89aba 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -680,7 +680,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
         if( ( bytesSentThisVector > 0U ) &&
             ( pIoVectIterator < &( pIoVec[ ioVecCount ] ) ) )
         {
-            ( ( uint8_t * ) pIoVectIterator->iov_base ) += bytesSentThisVector;
+            ( * ( ( uint8_t * ) pIoVectIterator->iov_base ) ) += bytesSentThisVector;
             pIoVectIterator->iov_len -= bytesSentThisVector;
         }
     }

From 21e7180e666c0081e7ba425533b26c1cbfd833ed Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 06:27:47 +0000
Subject: [PATCH 11/35] Add doxygen comments

---
 source/core_mqtt.c                     | 123 ++++++++++++++++++++++++-
 source/include/core_mqtt.h             |  28 +++---
 source/interface/transport_interface.h |   3 +
 3 files changed, 138 insertions(+), 16 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 9a2b89aba..405b3ffb0 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -56,11 +56,132 @@ static int32_t sendBuffer( MQTTContext_t * pContext,
                            size_t bytesToSend,
                            uint32_t timeout );
 
+/**
+ * @brief Sends MQTT connect without copying the users data into any buffer.
+ *
+ * @brief param[in] pContext Initialized MQTT context.
+ * @brief param[in] pConnectInfo MQTT CONNECT packet information.
+ * @brief param[in] pWillInfo Last Will and Testament. Pass NULL if Last Will and
+ * Testament is not used.
+ * @brief param[in] remainingLength the length of the connect packet.
+ *
+ * @note This operation may call the transport send function
+ * repeatedly to send bytes over the network until either:
+ * 1. The requested number of bytes @a remainingLength have been sent.
+ *                    OR
+ * 2. No byte cannot be sent over the network for the MQTT_SEND_RETRY_TIMEOUT_MS
+ * duration.
+ *                    OR
+ * 3. There is an error in sending data over the network.
+ *
+ * @return #MQTTSendFailed or #MQTTSuccess. 
+ */
 static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                             const MQTTConnectInfo_t * pConnectInfo,
                                             const MQTTPublishInfo_t * pWillInfo,
                                             size_t remainingLength );
 
+/**
+ * @brief Sends the vector array passed through the parameters over the network.
+ *
+ * @note The preference is given to 'write' function if it is present in the
+ * transport interface. Otherwise, a send call is made repeatedly to achieve the
+ * result.
+ *
+ * @param[in] pContext Initialized MQTT context.
+ * @param[in] pIoVec The vecotr array to be sent.
+ * @param[in] ioVecCount The number of elements in the array.
+ *
+ * @return The total number of bytes sent or the error code as received from the
+ * transport interface.
+ */
+static int32_t sendMessageVector( MQTTContext_t * pContext,
+                                  TransportOutVector_t * pIoVec,
+                                  size_t ioVecCount );
+
+/**
+ * @brief Add a string and its length after serializing it in a manner outlined by
+ * the MQTT specification.
+ *
+ * @param[in] serailizedLength Array of two bytes to which the vecotr will point.
+ * The array must remain in scope until the message has been sent.
+ * @param[in] string The string to be serialized.
+ * @param[in] length The length of the string to be serialized.
+ * @param[in] iterator The iterator pointing to the first element in the
+ * transport interface IO array.
+ * @param[out] updatedLength This parameter will be added to with the number of
+ * bytes added to the vector.
+ *
+ * @return The updated pointer to the vector array.
+ */
+static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
+                                                        uint8_t * string,
+                                                        uint8_t length,
+                                                        TransportOutVector_t * iterator,
+                                                        size_t * updatedLength );
+
+/**
+ * @brief Add the will and testament information along with the connection information
+ * to the given vector.
+ *
+ * @param[in] pConnectInfo Connection information of MQTT.
+ * @param[in] pWillInfo The last will and testament information.
+ * @param[out] totalMessageLength This parameter will be added to with the number of
+ * bytes added to the vector.
+ * @param[in] iterator The iterator pointing to the first element in the
+ * transport interface IO array.
+ * @param[out] serializedTopicLength This array will be updated with the topic field
+ * length in serialized MQTT format.
+ * @param[out] serializedPayloadLength This array will be updated with the payload
+ * field length in serialized MQTT format.
+ * @param[out] serializedUsernameLength This array will be updated with the user name
+ * field length in serialized MQTT format.
+ * @param[out] serializedPasswordLength This array will be updated with the password
+ * field length in serialized MQTT format.
+ * 
+ * @note All the arrays must stay in scope until the message contained in the vector has
+ * been sent.
+ */
+static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
+                                   const MQTTPublishInfo_t * pWillInfo,
+                                   size_t * totalMessageLength,
+                                   TransportOutVector_t * iterator,
+                                   uint8_t serializedTopicLength[ 2 ],
+                                   uint8_t serializedPayloadLength[ 2 ],
+                                   uint8_t serializedUsernameLength[ 2 ],
+                                   uint8_t serializedPasswordLength[ 2 ] );
+
+/**
+ * @brief Send MQTT SUBSCRIBE message without copying the user data into a buffer and
+ * directly sending it.
+ *
+ * @param[in] pContext Initialized MQTT context.
+ * @param[in] pSubscription MQTT subscription info.
+ * @param[in] packetId The packet ID of the subscribe packet
+ * @param[in] remainingLength The remaining length of the subscribe packet.
+ *
+ * @return #MQTTSuccess or #MQTTSendFailed.
+ */
+static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
+                                              const MQTTSubscribeInfo_t * pSubscription,
+                                              uint16_t packetId,
+                                              size_t remainingLength );
+
+/**
+ * @brief Send MQTT UNSUBSCRIBE message without copying the user data into a buffer and
+ * directly sending it.
+ *
+ * @param[in] pContext Initialized MQTT context.
+ * @param[in] pSubscription MQTT subscription info.
+ * @param[in] packetId The packet ID of the unsubscribe packet.
+ * @param[in] remainingLength The remaining length of the unsubscribe packet.
+ *
+ * @return #MQTTSuccess or #MQTTSendFailed.
+ */
+static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
+                                                const MQTTSubscribeInfo_t * pSubscription,
+                                                uint16_t packetId,
+                                                size_t remainingLength );
 /**
  * @brief Calculate the interval between two millisecond timestamps, including
  * when the later value has overflowed.
@@ -1515,7 +1636,7 @@ static MQTTStatus_t validateSubscribeUnsubscribeParams( const MQTTContext_t * pC
 /*-----------------------------------------------------------*/
 
 static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
-                                                        uint8_t string,
+                                                        uint8_t * string,
                                                         uint8_t length,
                                                         TransportOutVector_t * iterator,
                                                         size_t * updatedLength )
diff --git a/source/include/core_mqtt.h b/source/include/core_mqtt.h
index 361e3cf36..2b611f56f 100644
--- a/source/include/core_mqtt.h
+++ b/source/include/core_mqtt.h
@@ -425,12 +425,10 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
 /* @[declare_mqtt_connect] */
 
 /**
- * @brief Sends MQTT SUBSCRIBE for the given list of topic filters to
- * the broker.
+ * @brief Sends MQTT SUBSCRIBE for the given topic filter to the broker.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pSubscriptionList List of MQTT subscription info.
- * @param[in] subscriptionCount The number of elements in pSubscriptionList.
+ * @param[in] pSubscription MQTT subscription info.
  * @param[in] packetId Packet ID generated by #MQTT_GetPacketId.
  *
  * @return #MQTTNoMemory if the #MQTTContext_t.networkBuffer is too small to
@@ -451,25 +449,25 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
  * // This is assumed to be a list of filters we want to subscribe to.
  * const char * filters[ NUMBER_OF_SUBSCRIPTIONS ];
  *
- * // Set each subscription.
+ * // Subscribe to each subscription filter.
  * for( int i = 0; i < NUMBER_OF_SUBSCRIPTIONS; i++ )
  * {
  *      subscriptionList[ i ].qos = MQTTQoS0;
  *      // Each subscription needs a topic filter.
  *      subscriptionList[ i ].pTopicFilter = filters[ i ];
  *      subscriptionList[ i ].topicFilterLength = strlen( filters[ i ] );
- * }
- *
- * // Obtain a new packet id for the subscription.
- * packetId = MQTT_GetPacketId( pContext );
+ * 
+ *      // Obtain a new packet id for the subscription.
+ *      packetId = MQTT_GetPacketId( pContext );
  *
- * status = MQTT_Subscribe( pContext, &subscriptionList[ 0 ], NUMBER_OF_SUBSCRIPTIONS, packetId );
+ *      status = MQTT_Subscribe( pContext, &subscriptionList[ i ], packetId );
  *
- * if( status == MQTTSuccess )
- * {
- *      // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the SUBACK.
- *      // If the broker accepts the subscription we can now receive publishes
- *      // on the requested topics.
+ *      if( status == MQTTSuccess )
+ *      {
+ *           // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the SUBACK.
+ *           // If the broker accepts the subscription we can now receive publishes
+ *           // on the requested topics.
+ *      }
  * }
  * @endcode
  */
diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index c7b6de6df..25bd88091 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -243,6 +243,9 @@ typedef int32_t ( * TransportSend_t )( NetworkContext_t * pNetworkContext,
                                        size_t bytesToSend );
 /* @[define_transportsend] */
 
+/**
+ * @brief Transport vector structure for sending multiple messages.
+ */
 typedef struct TransportOutVector
 {
     const void * iov_base; /* Base address of data */

From 399803f91b4a51cf0b554724fa1f0dc9c7d64022 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 06:47:49 +0000
Subject: [PATCH 12/35] Fix doxygen part 2

---
 source/include/core_mqtt.h            | 24 ++++++------
 source/include/core_mqtt_serializer.h | 54 +++++++++++++++++++++++++--
 2 files changed, 62 insertions(+), 16 deletions(-)

diff --git a/source/include/core_mqtt.h b/source/include/core_mqtt.h
index 2b611f56f..8a035b21d 100644
--- a/source/include/core_mqtt.h
+++ b/source/include/core_mqtt.h
@@ -539,12 +539,10 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
 /* @[declare_mqtt_ping] */
 
 /**
- * @brief Sends MQTT UNSUBSCRIBE for the given list of topic filters to
- * the broker.
+ * @brief Sends MQTT UNSUBSCRIBE for the topic filter to the broker.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pSubscriptionList List of MQTT subscription info.
- * @param[in] subscriptionCount The number of elements in pSubscriptionList.
+ * @param[in] pSubscription MQTT subscription info.
  * @param[in] packetId packet ID generated by #MQTT_GetPacketId.
  *
  * @return #MQTTNoMemory if the #MQTTContext_t.networkBuffer is too small to
@@ -572,17 +570,17 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
  *      unsubscribeList[ i ].topicFilterLength = strlen( filters[ i ] );
  *
  *      // The QoS field of MQTT_SubscribeInfo_t is unused for unsubscribing.
- * }
- *
- * // Obtain a new packet id for the unsubscribe request.
- * packetId = MQTT_GetPacketId( pContext );
+ * 
+ *      // Obtain a new packet id for the unsubscribe request.
+ *      packetId = MQTT_GetPacketId( pContext );
  *
- * status = MQTT_Unsubscribe( pContext, &unsubscribeList[ 0 ], NUMBER_OF_SUBSCRIPTIONS, packetId );
+ *      status = MQTT_Unsubscribe( pContext, &unsubscribeList[ i ], packetId );
  *
- * if( status == MQTTSuccess )
- * {
- *      // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the UNSUBACK.
- *      // After this the broker should no longer send publishes for these topics.
+ *      if( status == MQTTSuccess )
+ *      {
+ *           // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the UNSUBACK.
+ *           // After this the broker should no longer send publishes for these topics.
+ *      }
  * }
  * @endcode
  */
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 644f30c7d..7341a7ba5 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -862,10 +862,9 @@ MQTTStatus_t MQTT_SerializePublish( const MQTTPublishInfo_t * pPublishInfo,
  * as the size returned by #MQTT_GetPublishPacketSize.
  *
  * @param[in] pPublishInfo MQTT PUBLISH packet parameters.
- * @param[in] packetId packet ID generated by #MQTT_GetPacketId.
  * @param[in] remainingLength Remaining Length provided by #MQTT_GetPublishPacketSize.
- * @param[out] pFixedBuffer Buffer for packet serialization.
- * @param[out] pHeaderSize Size of the serialized MQTT PUBLISH header.
+ * @param[out] pBuffer Buffer for packet serialization.
+ * @param[out] headerSize Size of the serialized MQTT PUBLISH header.
  *
  * @return #MQTTNoMemory if pFixedBuffer is too small to hold the MQTT packet;
  * #MQTTBadParameter if invalid parameters are passed;
@@ -1315,15 +1314,64 @@ MQTTStatus_t MQTT_GetIncomingPacketTypeAndLength( TransportRecv_t readFunc,
                                                   MQTTPacketInfo_t * pIncomingPacket );
 /* @[declare_mqtt_getincomingpackettypeandlength] */
 
+/**
+ * @brief Serialize the fixed part of the connect packet header.
+ *
+ * @param[out] pIndex Pointer to the buffer where the header is to
+ * be serialized.
+ * @param[in] pConnectInfo The connect information.
+ * @param[in] pWillInfo The last will and testament information.
+ * @param[in] remainingLength The remaining length of the packet to be
+ * serialized.
+ *
+ * @return A pointer to the end of the encoded string.
+ */
+
+/**
+ * @cond DOXYGEN_IGNORE
+ * Doxygen should ignore this definition, this function is private.
+ */
 uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
                                             const MQTTConnectInfo_t * pConnectInfo,
                                             const MQTTPublishInfo_t * pWillInfo,
                                             size_t remainingLength );
 
+/**
+ * @brief Serialize the fixed part of the subscribe packet header.
+ *
+ * @param[in] remainingLength The remaining length of the packet to be
+ * serialized.
+ * @param[in] pIndex Pointer to the buffer where the header is to
+ * be serialized.
+ * @param[in] packetId The packet ID to be serialized.
+ *
+ * @return A pointer to the end of the encoded string.
+ */
+
+/**
+ * @cond DOXYGEN_IGNORE
+ * Doxygen should ignore this definition, this function is private.
+ */
 uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength,
                                          uint8_t * pIndex,
                                          uint16_t packetId );
 
+/**
+ * @brief Serialize the fixed part of the unsubscribe packet header.
+ *
+ * @param[in] remainingLength The remaining length of the packet to be
+ * serialized.
+ * @param[in] pIndex Pointer to the buffer where the header is to
+ * be serialized.
+ * @param[in] packetId The packet ID to be serialized.
+ *
+ * @return A pointer to the end of the encoded string.
+ */
+
+/**
+ * @cond DOXYGEN_IGNORE
+ * Doxygen should ignore this definition, this function is private.
+ */
 uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength,
                                            uint8_t * pIndex,
                                            uint16_t packetId );

From 2caf1966dd325be45b32e31f1573a52824e7877b Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 06:51:31 +0000
Subject: [PATCH 13/35] Doxygen fix part 3

---
 source/include/core_mqtt_serializer.h  |  3 +++
 source/interface/transport_interface.h | 11 +++++++++--
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 7341a7ba5..e36255013 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -1335,6 +1335,7 @@ uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
                                             const MQTTConnectInfo_t * pConnectInfo,
                                             const MQTTPublishInfo_t * pWillInfo,
                                             size_t remainingLength );
+/** @endcond */
 
 /**
  * @brief Serialize the fixed part of the subscribe packet header.
@@ -1355,6 +1356,7 @@ uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
 uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength,
                                          uint8_t * pIndex,
                                          uint16_t packetId );
+/** @endcond */
 
 /**
  * @brief Serialize the fixed part of the unsubscribe packet header.
@@ -1375,6 +1377,7 @@ uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength,
 uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength,
                                            uint8_t * pIndex,
                                            uint16_t packetId );
+/** @endcond */
 
 /* *INDENT-OFF* */
 #ifdef __cplusplus
diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index 25bd88091..a884e7ee2 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -248,8 +248,15 @@ typedef int32_t ( * TransportSend_t )( NetworkContext_t * pNetworkContext,
  */
 typedef struct TransportOutVector
 {
-    const void * iov_base; /* Base address of data */
-    size_t iov_len;        /* Length of data in buffer */
+    /**
+     * @brief Base address of data.
+     */
+    const void * iov_base;
+
+    /**
+     * @brief Length of data in buffer.
+     */
+    size_t iov_len;
 } TransportOutVector_t;
 
 /**

From cb533e5e3ed05957e6582cf08e78cf17d84b04dc Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 07:04:18 +0000
Subject: [PATCH 14/35] Fix doxygen part 4

---
 source/include/core_mqtt_serializer.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index e36255013..5887f3bba 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -1315,6 +1315,7 @@ MQTTStatus_t MQTT_GetIncomingPacketTypeAndLength( TransportRecv_t readFunc,
 /* @[declare_mqtt_getincomingpackettypeandlength] */
 
 /**
+ * @fn uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex, const MQTTConnectInfo_t * pConnectInfo, const MQTTPublishInfo_t * pWillInfo, size_t remainingLength );
  * @brief Serialize the fixed part of the connect packet header.
  *
  * @param[out] pIndex Pointer to the buffer where the header is to
@@ -1338,6 +1339,7 @@ uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex,
 /** @endcond */
 
 /**
+ * @fn  uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength, uint8_t * pIndex, uint16_t packetId );
  * @brief Serialize the fixed part of the subscribe packet header.
  *
  * @param[in] remainingLength The remaining length of the packet to be
@@ -1359,6 +1361,7 @@ uint8_t * MQTT_SerializeSubscribeHeader( size_t remainingLength,
 /** @endcond */
 
 /**
+ * @fn uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength, uint8_t * pIndex, uint16_t packetId );
  * @brief Serialize the fixed part of the unsubscribe packet header.
  *
  * @param[in] remainingLength The remaining length of the packet to be

From c16927c84f88fbd9f404588156bfe1860f3f71b9 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 07:19:33 +0000
Subject: [PATCH 15/35] Fix some checks

---
 lexicon.txt                           |  9 +++++++++
 source/core_mqtt.c                    | 11 ++++++-----
 source/include/core_mqtt.h            |  4 ++--
 source/include/core_mqtt_serializer.h | 11 +----------
 4 files changed, 18 insertions(+), 17 deletions(-)

diff --git a/lexicon.txt b/lexicon.txt
index 818ba164c..1718dc35a 100644
--- a/lexicon.txt
+++ b/lexicon.txt
@@ -235,6 +235,7 @@ pfilterindex
 pfixedbuffer
 pheadersize
 pincomingpacket
+pindex
 pingreq
 pingreqs
 pingreqsendtimems
@@ -281,6 +282,7 @@ psuback
 psubackpacket
 psubscribeinfo
 psubscribes
+psubscription
 psubscriptionlist
 ptopic
 ptopicfilter
@@ -332,6 +334,11 @@ serializeack
 serializeconnect
 serializeconnectpacket
 serializedisconnect
+serailizedlength
+serializedpasswordlength
+serializedpayloadlength
+serializedtopiclength
+serializedusernamelength
 serializepayload
 serializepingreq
 serializepublish
@@ -378,6 +385,7 @@ tlssend
 toolchain
 topicfilterlength
 topicnamelength
+totalmessagelength
 tr
 transportcallback
 transportinterface
@@ -394,6 +402,7 @@ uint
 un
 unsuback
 unsubscribelist
+updatedlength
 updatestateack
 updatestatepublish
 updatestatestatus
diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 405b3ffb0..3240f4cdc 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -74,7 +74,7 @@ static int32_t sendBuffer( MQTTContext_t * pContext,
  *                    OR
  * 3. There is an error in sending data over the network.
  *
- * @return #MQTTSendFailed or #MQTTSuccess. 
+ * @return #MQTTSendFailed or #MQTTSuccess.
  */
 static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                             const MQTTConnectInfo_t * pConnectInfo,
@@ -89,7 +89,7 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
  * result.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pIoVec The vecotr array to be sent.
+ * @param[in] pIoVec The vector array to be sent.
  * @param[in] ioVecCount The number of elements in the array.
  *
  * @return The total number of bytes sent or the error code as received from the
@@ -103,7 +103,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
  * @brief Add a string and its length after serializing it in a manner outlined by
  * the MQTT specification.
  *
- * @param[in] serailizedLength Array of two bytes to which the vecotr will point.
+ * @param[in] serailizedLength Array of two bytes to which the vector will point.
  * The array must remain in scope until the message has been sent.
  * @param[in] string The string to be serialized.
  * @param[in] length The length of the string to be serialized.
@@ -138,7 +138,7 @@ static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength
  * field length in serialized MQTT format.
  * @param[out] serializedPasswordLength This array will be updated with the password
  * field length in serialized MQTT format.
- * 
+ *
  * @note All the arrays must stay in scope until the message contained in the vector has
  * been sent.
  */
@@ -182,6 +182,7 @@ static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
                                                 const MQTTSubscribeInfo_t * pSubscription,
                                                 uint16_t packetId,
                                                 size_t remainingLength );
+
 /**
  * @brief Calculate the interval between two millisecond timestamps, including
  * when the later value has overflowed.
@@ -801,7 +802,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
         if( ( bytesSentThisVector > 0U ) &&
             ( pIoVectIterator < &( pIoVec[ ioVecCount ] ) ) )
         {
-            ( * ( ( uint8_t * ) pIoVectIterator->iov_base ) ) += bytesSentThisVector;
+            ( *( ( uint8_t * ) pIoVectIterator->iov_base ) ) += bytesSentThisVector;
             pIoVectIterator->iov_len -= bytesSentThisVector;
         }
     }
diff --git a/source/include/core_mqtt.h b/source/include/core_mqtt.h
index 8a035b21d..5b5de6d8f 100644
--- a/source/include/core_mqtt.h
+++ b/source/include/core_mqtt.h
@@ -456,7 +456,7 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
  *      // Each subscription needs a topic filter.
  *      subscriptionList[ i ].pTopicFilter = filters[ i ];
  *      subscriptionList[ i ].topicFilterLength = strlen( filters[ i ] );
- * 
+ *
  *      // Obtain a new packet id for the subscription.
  *      packetId = MQTT_GetPacketId( pContext );
  *
@@ -570,7 +570,7 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
  *      unsubscribeList[ i ].topicFilterLength = strlen( filters[ i ] );
  *
  *      // The QoS field of MQTT_SubscribeInfo_t is unused for unsubscribing.
- * 
+ *
  *      // Obtain a new packet id for the unsubscribe request.
  *      packetId = MQTT_GetPacketId( pContext );
  *
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 5887f3bba..3240c2594 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -848,27 +848,18 @@ MQTTStatus_t MQTT_SerializePublish( const MQTTPublishInfo_t * pPublishInfo,
                                     const MQTTFixedBuffer_t * pFixedBuffer );
 /* @[declare_mqtt_serializepublish] */
 
-/* TODO: Re-write the brief comments below. */
 /**
  * @brief Serialize an MQTT PUBLISH packet header without the topic string in the
  * given buffer. This function will add the topic string length to the provided
  * buffer. This helps reduce an unnecessary copy of the topic string into the
  * buffer.
  *
- * #MQTT_GetPublishPacketSize should be called with @p pPublishInfo before
- * invoking this function to get the size of the required buffer and
- * @p remainingLength. The @p remainingLength must be the same as returned by
- * #MQTT_GetPublishPacketSize. The buffer must be at least as large
- * as the size returned by #MQTT_GetPublishPacketSize.
- *
  * @param[in] pPublishInfo MQTT PUBLISH packet parameters.
  * @param[in] remainingLength Remaining Length provided by #MQTT_GetPublishPacketSize.
  * @param[out] pBuffer Buffer for packet serialization.
  * @param[out] headerSize Size of the serialized MQTT PUBLISH header.
  *
- * @return #MQTTNoMemory if pFixedBuffer is too small to hold the MQTT packet;
- * #MQTTBadParameter if invalid parameters are passed;
- * #MQTTSuccess otherwise.
+ * @return #MQTTSuccess if the serialization is successful. Otherwise, #MQTTBadParameter.
  */
 MQTTStatus_t MQTT_SerializePublishHeaderWithoutTopic( const MQTTPublishInfo_t * pPublishInfo,
                                                       size_t remainingLength,

From effd5d4a6bf1992b9d4c919460bf040ad3a15733 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 07:23:11 +0000
Subject: [PATCH 16/35] Fix memory tables

---
 docs/doxygen/include/size_table.md | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/docs/doxygen/include/size_table.md b/docs/doxygen/include/size_table.md
index 9f085682c..3f5d85312 100644
--- a/docs/doxygen/include/size_table.md
+++ b/docs/doxygen/include/size_table.md
@@ -9,8 +9,8 @@
     </tr>
     <tr>
         <td>core_mqtt.c</td>
+        <td><center>3.5K</center></td>
         <td><center>3.1K</center></td>
-        <td><center>2.7K</center></td>
     </tr>
     <tr>
         <td>core_mqtt_state.c</td>
@@ -19,12 +19,12 @@
     </tr>
     <tr>
         <td>core_mqtt_serializer.c</td>
-        <td><center>2.5K</center></td>
-        <td><center>2.0K</center></td>
+        <td><center>2.7K</center></td>
+        <td><center>2.1K</center></td>
     </tr>
     <tr>
         <td><b>Total estimates</b></td>
-        <td><b><center>7.0K</center></b></td>
-        <td><b><center>5.8K</center></b></td>
+        <td><b><center>7.6K</center></b></td>
+        <td><b><center>6.3K</center></b></td>
     </tr>
 </table>

From c1018fbc7677d34a0daa7f5c7895afdb19944aae Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 07:30:04 +0000
Subject: [PATCH 17/35] Fix some small errors

---
 source/core_mqtt.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 3240f4cdc..3e274072d 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -115,7 +115,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
  * @return The updated pointer to the vector array.
  */
 static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
-                                                        uint8_t * string,
+                                                        const uint8_t * string,
                                                         uint8_t length,
                                                         TransportOutVector_t * iterator,
                                                         size_t * updatedLength );
@@ -144,7 +144,7 @@ static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength
  */
 static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
                                    const MQTTPublishInfo_t * pWillInfo,
-                                   size_t * totalMessageLength,
+                                   size_t * pTotalMessageLength,
                                    TransportOutVector_t * iterator,
                                    uint8_t serializedTopicLength[ 2 ],
                                    uint8_t serializedPayloadLength[ 2 ],
@@ -757,7 +757,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
     pIoVectIterator = pIoVec;
 
     while( ( pContext->getTime() < timeoutTime ) &&
-           ( bytesSentOrError < bytesToSend ) )
+           ( bytesSentOrError < ( int32_t ) bytesToSend ) )
     {
         int32_t sendResult;
         uint32_t bytesSentThisVector = 0U;
@@ -1637,7 +1637,7 @@ static MQTTStatus_t validateSubscribeUnsubscribeParams( const MQTTContext_t * pC
 /*-----------------------------------------------------------*/
 
 static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
-                                                        uint8_t * string,
+                                                        const uint8_t * string,
                                                         uint8_t length,
                                                         TransportOutVector_t * iterator,
                                                         size_t * updatedLength )
@@ -1829,7 +1829,7 @@ static MQTTStatus_t sendPublishWithoutCopy( MQTTContext_t * pContext,
 
 static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
                                    const MQTTPublishInfo_t * pWillInfo,
-                                   size_t * totalMessageLength,
+                                   size_t * pTotalMessageLength,
                                    TransportOutVector_t * iterator,
                                    uint8_t serializedTopicLength[ 2 ],
                                    uint8_t serializedPayloadLength[ 2 ],
@@ -1843,14 +1843,14 @@ static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
                                              pWillInfo->pTopicName,
                                              pWillInfo->topicNameLength,
                                              iterator,
-                                             &totalMessageLength );
+                                             pTotalMessageLength );
 
         /* Serialize the payload. */
         iterator = addEncodedStringToVector( serializedPayloadLength,
                                              pWillInfo->pPayload,
                                              pWillInfo->payloadLength,
                                              iterator,
-                                             &totalMessageLength );
+                                             pTotalMessageLength );
     }
 
     /* Encode the user name if provided. */
@@ -1861,7 +1861,7 @@ static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
                                              pConnectInfo->pUserName,
                                              pConnectInfo->userNameLength,
                                              iterator,
-                                             &totalMessageLength );
+                                             pTotalMessageLength );
     }
 
     /* Encode the password if provided. */
@@ -1872,7 +1872,7 @@ static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
                                              pConnectInfo->pPassword,
                                              pConnectInfo->passwordLength,
                                              iterator,
-                                             &totalMessageLength );
+                                             pTotalMessageLength );
     }
 }
 

From e4bffa0ff1dd5e4a75148cea98e4cad9bed510e6 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 11:03:29 -0700
Subject: [PATCH 18/35] Fix compiler warnings and breaking CI checks from
 previous commit

---
 docs/doxygen/include/size_table.md    | 10 +++++-----
 source/core_mqtt.c                    | 20 ++++++++------------
 source/core_mqtt_serializer.c         |  1 -
 source/include/core_mqtt_serializer.h |  7 +++----
 4 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/docs/doxygen/include/size_table.md b/docs/doxygen/include/size_table.md
index 08f88b5fa..cd80abff5 100644
--- a/docs/doxygen/include/size_table.md
+++ b/docs/doxygen/include/size_table.md
@@ -9,7 +9,7 @@
     </tr>
     <tr>
         <td>core_mqtt.c</td>
-        <td><center>3.5K</center></td>
+        <td><center>3.6K</center></td>
         <td><center>3.1K</center></td>
     </tr>
     <tr>
@@ -19,12 +19,12 @@
     </tr>
     <tr>
         <td>core_mqtt_serializer.c</td>
-        <td><center>2.7K</center></td>
-        <td><center>2.1K</center></td>
+        <td><center>2.8K</center></td>
+        <td><center>2.2K</center></td>
     </tr>
     <tr>
         <td><b>Total estimates</b></td>
-        <td><b><center>7.6K</center></b></td>
-        <td><b><center>6.3K</center></b></td>
+        <td><b><center>7.9K</center></b></td>
+        <td><b><center>6.4K</center></b></td>
     </tr>
 </table>
diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 778e4be3b..9f5711207 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -115,8 +115,8 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
  * @return The updated pointer to the vector array.
  */
 static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
-                                                        const uint8_t * string,
-                                                        uint8_t length,
+                                                        const char * const string,
+                                                        uint16_t length,
                                                         TransportOutVector_t * iterator,
                                                         size_t * updatedLength );
 
@@ -126,7 +126,7 @@ static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength
  *
  * @param[in] pConnectInfo Connection information of MQTT.
  * @param[in] pWillInfo The last will and testament information.
- * @param[out] totalMessageLength This parameter will be added to with the number of
+ * @param[out] pTotalMessageLength This parameter will be added to with the number of
  * bytes added to the vector.
  * @param[in] iterator The iterator pointing to the first element in the
  * transport interface IO array.
@@ -1757,8 +1757,8 @@ static MQTTStatus_t validateSubscribeUnsubscribeParams( const MQTTContext_t * pC
 /*-----------------------------------------------------------*/
 
 static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength[ 2 ],
-                                                        const uint8_t * string,
-                                                        uint8_t length,
+                                                        const char * const string,
+                                                        uint16_t length,
                                                         TransportOutVector_t * iterator,
                                                         size_t * updatedLength )
 {
@@ -1968,7 +1968,7 @@ static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
         /* Serialize the payload. */
         iterator = addEncodedStringToVector( serializedPayloadLength,
                                              pWillInfo->pPayload,
-                                             pWillInfo->payloadLength,
+                                             ( uint16_t ) pWillInfo->payloadLength,
                                              iterator,
                                              pTotalMessageLength );
     }
@@ -2004,7 +2004,6 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                             size_t remainingLength )
 {
     MQTTStatus_t status = MQTTSuccess;
-    size_t connectPacketSize = 0;
     TransportOutVector_t * iterator;
     size_t ioVectorLength = 0U;
     size_t totalMessageLength = 0U;
@@ -2057,8 +2056,8 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                              iterator,
                                              &totalMessageLength );
 
-        addWillAndConnectInfo( pWillInfo,
-                               pConnectInfo,
+        addWillAndConnectInfo( pConnectInfo,
+                               pWillInfo,
                                &totalMessageLength,
                                iterator,
                                serializedTopicLength,
@@ -2399,7 +2398,6 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
                            bool * pSessionPresent )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
-    int32_t bytesSent;
     MQTTStatus_t status = MQTTSuccess;
     MQTTPacketInfo_t incomingPacket = { 0 };
 
@@ -2476,7 +2474,6 @@ MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
                              uint16_t packetId )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
-    int32_t bytesSent = 0;
 
     /* Validate arguments. */
     MQTTStatus_t status = validateSubscribeUnsubscribeParams( pContext,
@@ -2672,7 +2669,6 @@ MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
                                uint16_t packetId )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
-    int32_t bytesSent = 0;
 
     /* Validate arguments. */
     MQTTStatus_t status = validateSubscribeUnsubscribeParams( pContext,
diff --git a/source/core_mqtt_serializer.c b/source/core_mqtt_serializer.c
index 7189492cb..b553c1931 100644
--- a/source/core_mqtt_serializer.c
+++ b/source/core_mqtt_serializer.c
@@ -1522,7 +1522,6 @@ static void serializeConnectPacket( const MQTTConnectInfo_t * pConnectInfo,
                                     size_t remainingLength,
                                     const MQTTFixedBuffer_t * pFixedBuffer )
 {
-    uint8_t connectFlags = 0U;
     uint8_t * pIndex = NULL;
 
     assert( pConnectInfo != NULL );
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index f874dcfd2..587463112 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -1387,14 +1387,13 @@ uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength,
  * #MQTTPacketInfo_t is not valid until this routine has been invoked.
  *
  * @param[in] pBuffer The buffer holding the raw data to be processed
- * @param[in] pIndex Pointer to the index within the buffer to marking the end of raw data
- *            available.
- * @param[in] pIncomingPacket Structure used to hold the fields of the
+ * @param[in] pIndex Pointer to the index within the buffer to marking the end
+ *            of raw data available.
+ * @param[out] pIncomingPacket Structure used to hold the fields of the
  *            incoming packet.
  *
  * @return #MQTTSuccess on successful extraction of type and length,
  * #MQTTBadParameter if @p pIncomingPacket is invalid,
- * #MQTTRecvFailed on transport receive failure,
  * #MQTTBadResponse if an invalid packet is read, and
  * #MQTTNoDataAvailable if there is nothing to read.
  */

From 5fe0678eaf98fd974bde46d78db0dbf552e1b8d6 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 11:10:59 -0700
Subject: [PATCH 19/35] Fix spell check and doxygen

---
 lexicon.txt                           |  1 +
 source/include/core_mqtt_serializer.h | 46 ++++++++++++++-------------
 2 files changed, 25 insertions(+), 22 deletions(-)

diff --git a/lexicon.txt b/lexicon.txt
index 7a9a70492..3877e2127 100644
--- a/lexicon.txt
+++ b/lexicon.txt
@@ -288,6 +288,7 @@ psubscriptionlist
 ptopic
 ptopicfilter
 ptopicname
+ptotalmessagelength
 ptr
 ptransport
 ptransportinterface
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 587463112..73e7148b2 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -1311,6 +1311,30 @@ MQTTStatus_t MQTT_GetIncomingPacketTypeAndLength( TransportRecv_t readFunc,
                                                   MQTTPacketInfo_t * pIncomingPacket );
 /* @[declare_mqtt_getincomingpackettypeandlength] */
 
+/*
+ * @brief Extract the MQTT packet type and length from incoming packet.
+ *
+ * This function must be called for every incoming packet to retrieve the
+ * #MQTTPacketInfo_t.type and #MQTTPacketInfo_t.remainingLength. A
+ * #MQTTPacketInfo_t is not valid until this routine has been invoked.
+ *
+ * @param[in] pBuffer The buffer holding the raw data to be processed
+ * @param[in] pIndex Pointer to the index within the buffer to marking the end
+ *            of raw data available.
+ * @param[out] pIncomingPacket Structure used to hold the fields of the
+ *            incoming packet.
+ *
+ * @return #MQTTSuccess on successful extraction of type and length,
+ * #MQTTBadParameter if @p pIncomingPacket is invalid,
+ * #MQTTBadResponse if an invalid packet is read, and
+ * #MQTTNoDataAvailable if there is nothing to read.
+ */
+ /* @[declare_mqtt_processincomingpackettypeandlength] */
+MQTTStatus_t MQTT_ProcessIncomingPacketTypeAndLength( uint8_t * pBuffer,
+                                                      size_t * pIndex,
+                                                      MQTTPacketInfo_t * pIncomingPacket );
+/* @[declare_mqtt_processincomingpackettypeandlength] */
+
 /**
  * @fn uint8_t * MQTT_SerializeConnectFixedHeader( uint8_t * pIndex, const MQTTConnectInfo_t * pConnectInfo, const MQTTPublishInfo_t * pWillInfo, size_t remainingLength );
  * @brief Serialize the fixed part of the connect packet header.
@@ -1379,28 +1403,6 @@ uint8_t * MQTT_SerializeUnsubscribeHeader( size_t remainingLength,
                                            uint16_t packetId );
 /** @endcond */
 
-/*
- * @brief Extract the MQTT packet type and length from incoming packet.
- *
- * This function must be called for every incoming packet to retrieve the
- * #MQTTPacketInfo_t.type and #MQTTPacketInfo_t.remainingLength. A
- * #MQTTPacketInfo_t is not valid until this routine has been invoked.
- *
- * @param[in] pBuffer The buffer holding the raw data to be processed
- * @param[in] pIndex Pointer to the index within the buffer to marking the end
- *            of raw data available.
- * @param[out] pIncomingPacket Structure used to hold the fields of the
- *            incoming packet.
- *
- * @return #MQTTSuccess on successful extraction of type and length,
- * #MQTTBadParameter if @p pIncomingPacket is invalid,
- * #MQTTBadResponse if an invalid packet is read, and
- * #MQTTNoDataAvailable if there is nothing to read.
- */
-MQTTStatus_t MQTT_ProcessIncomingPacketTypeAndLength( uint8_t * pBuffer,
-                                                      size_t * pIndex,
-                                                      MQTTPacketInfo_t * pIncomingPacket );
-
 /* *INDENT-OFF* */
 #ifdef __cplusplus
     }

From e4cfbadb413d21cf5a50c3f970a17b858b9ed781 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 18:46:17 +0000
Subject: [PATCH 20/35] Fix a couple of CBMC proofs

---
 source/core_mqtt.c                                    |  4 ++--
 source/include/core_mqtt_serializer.h                 |  2 +-
 .../proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c    | 10 +++-------
 test/cbmc/proofs/MQTT_Subscribe/Makefile              | 11 +++++++----
 .../MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c       | 10 +++-------
 test/cbmc/proofs/MQTT_Unsubscribe/Makefile            |  7 +++++--
 test/cbmc/sources/mqtt_cbmc_state.c                   |  1 +
 7 files changed, 22 insertions(+), 23 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 9f5711207..c4b154d80 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -1791,7 +1791,7 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
                                               size_t remainingLength )
 {
     MQTTStatus_t status = MQTTSuccess;
-    uint8_t subscribeheader[ 5 ];
+    uint8_t subscribeheader[ 7 ];
     uint8_t * pIndex;
     TransportOutVector_t pIoVector[ 4 ];
     TransportOutVector_t * pIterator;
@@ -1842,7 +1842,7 @@ static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
                                                 size_t remainingLength )
 {
     MQTTStatus_t status = MQTTSuccess;
-    uint8_t unsubscribeheader[ 5 ];
+    uint8_t unsubscribeheader[ 7 ];
     uint8_t * pIndex;
     TransportOutVector_t pIoVector[ 4 ];
     TransportOutVector_t * pIterator;
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 73e7148b2..002b44d3e 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -1311,7 +1311,7 @@ MQTTStatus_t MQTT_GetIncomingPacketTypeAndLength( TransportRecv_t readFunc,
                                                   MQTTPacketInfo_t * pIncomingPacket );
 /* @[declare_mqtt_getincomingpackettypeandlength] */
 
-/*
+/**
  * @brief Extract the MQTT packet type and length from incoming packet.
  *
  * This function must be called for every incoming packet to retrieve the
diff --git a/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c b/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c
index d6bf4a374..2084be6cb 100644
--- a/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c
+++ b/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c
@@ -37,12 +37,8 @@ void harness()
     pContext = allocateMqttContext( NULL );
     __CPROVER_assume( isValidMqttContext( pContext ) );
 
-    /* Please see the default bound description on SUBSCRIPTION_COUNT_MAX in
-     * mqtt_cbmc_state.c for more information. */
-    __CPROVER_assume( subscriptionCount < SUBSCRIPTION_COUNT_MAX );
+    pSubscriptionList = allocateMqttSubscriptionList( NULL, 1U );
+    __CPROVER_assume( isValidMqttSubscriptionList( pSubscriptionList, 1U ) );
 
-    pSubscriptionList = allocateMqttSubscriptionList( NULL, subscriptionCount );
-    __CPROVER_assume( isValidMqttSubscriptionList( pSubscriptionList, subscriptionCount ) );
-
-    MQTT_Subscribe( pContext, pSubscriptionList, subscriptionCount, packetId );
+    MQTT_Subscribe( pContext, pSubscriptionList, packetId );
 }
diff --git a/test/cbmc/proofs/MQTT_Subscribe/Makefile b/test/cbmc/proofs/MQTT_Subscribe/Makefile
index c6d2f9140..53fbc3ce3 100644
--- a/test/cbmc/proofs/MQTT_Subscribe/Makefile
+++ b/test/cbmc/proofs/MQTT_Subscribe/Makefile
@@ -30,22 +30,25 @@ MAX_NETWORK_SEND_TRIES=3
 # mqtt_cbmc_state.c for more information on this bound. This is set to 2
 # currently to have the proof run quickly.
 SUBSCRIPTION_COUNT_MAX=2
+SUBSCRIBE_PACKET_VECTORS = 5
 
 DEFINES += -DMAX_NETWORK_SEND_TRIES=$(MAX_NETWORK_SEND_TRIES)
 DEFINES += -DSUBSCRIPTION_COUNT_MAX=$(SUBSCRIPTION_COUNT_MAX)
 INCLUDES +=
 
 REMOVE_FUNCTION_BODY +=
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 UNWINDSET += allocateMqttSubscriptionList.0:$(SUBSCRIPTION_COUNT_MAX)
-UNWINDSET += isValidMqttSubscriptionList.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_calculateSubscriptionPacketSize.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += MQTT_SerializeSubscribe.0:$(SUBSCRIPTION_COUNT_MAX)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${SUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${SUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${SUBSCRIBE_PACKET_VECTORS}
 # The encodeRemainingLength loop is unwound 5 times because encodeRemainingLength()
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
diff --git a/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c b/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c
index dc595df92..0fe1be53c 100644
--- a/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c
+++ b/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c
@@ -37,12 +37,8 @@ void harness()
     pContext = allocateMqttContext( NULL );
     __CPROVER_assume( isValidMqttContext( pContext ) );
 
-    /* Please see the default bound description on SUBSCRIPTION_COUNT_MAX in
-     * mqtt_cbmc_state.c for more information. */
-    __CPROVER_assume( subscriptionCount < SUBSCRIPTION_COUNT_MAX );
+    pSubscriptionList = allocateMqttSubscriptionList( NULL, 1U );
+    __CPROVER_assume( isValidMqttSubscriptionList( pSubscriptionList, 1U ) );
 
-    pSubscriptionList = allocateMqttSubscriptionList( NULL, subscriptionCount );
-    __CPROVER_assume( isValidMqttSubscriptionList( pSubscriptionList, subscriptionCount ) );
-
-    MQTT_Unsubscribe( pContext, pSubscriptionList, subscriptionCount, packetId );
+    MQTT_Unsubscribe( pContext, pSubscriptionList, packetId );
 }
diff --git a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
index 468468c20..b944a90af 100644
--- a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
+++ b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
@@ -30,6 +30,7 @@ MAX_NETWORK_SEND_TRIES=3
 # mqtt_cbmc_state.c for more information on this bound. This is set to 2
 # currently to have the proof run quickly.
 SUBSCRIPTION_COUNT_MAX=2
+UNSUBSCRIBE_PACKET_VECTORS = 5
 
 DEFINES += -DMAX_NETWORK_SEND_TRIES=$(MAX_NETWORK_SEND_TRIES)
 DEFINES += -DSUBSCRIPTION_COUNT_MAX=$(SUBSCRIPTION_COUNT_MAX)
@@ -41,11 +42,13 @@ REMOVE_FUNCTION_BODY +=
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 UNWINDSET += allocateMqttSubscriptionList.0:$(SUBSCRIPTION_COUNT_MAX)
-UNWINDSET += isValidMqttSubscriptionList.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_calculateSubscriptionPacketSize.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += MQTT_SerializeUnsubscribe.0:$(SUBSCRIPTION_COUNT_MAX)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${SUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${SUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${SUBSCRIBE_PACKET_VECTORS}
 # The encodeRemainingLength loop is unwound 5 times because encodeRemainingLength()
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
diff --git a/test/cbmc/sources/mqtt_cbmc_state.c b/test/cbmc/sources/mqtt_cbmc_state.c
index 026b363b2..3bb2676ad 100644
--- a/test/cbmc/sources/mqtt_cbmc_state.c
+++ b/test/cbmc/sources/mqtt_cbmc_state.c
@@ -199,6 +199,7 @@ MQTTContext_t * allocateMqttContext( MQTTContext_t * pContext )
          * function in core_mqtt.h. */
         pTransportInterface->recv = NetworkInterfaceReceiveStub;
         pTransportInterface->send = NetworkInterfaceSendStub;
+        pTransportInterface->writev = NULL;
     }
 
     pNetworkBuffer = allocateMqttFixedBuffer( NULL );

From ab7fb14aa258eaae28a10bc0ce69fb528961a933 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 19:10:30 +0000
Subject: [PATCH 21/35] Fix ping and publish proofs

---
 test/cbmc/proofs/MQTT_Ping/Makefile    | 2 +-
 test/cbmc/proofs/MQTT_Publish/Makefile | 7 ++++++-
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/test/cbmc/proofs/MQTT_Ping/Makefile b/test/cbmc/proofs/MQTT_Ping/Makefile
index edcee27bf..c0024f4fa 100644
--- a/test/cbmc/proofs/MQTT_Ping/Makefile
+++ b/test/cbmc/proofs/MQTT_Ping/Makefile
@@ -34,7 +34,7 @@ INCLUDES +=
 # occurs. Please see NetworkInterfaceReceiveStub in
 # test/cbmc/stubs/network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c
diff --git a/test/cbmc/proofs/MQTT_Publish/Makefile b/test/cbmc/proofs/MQTT_Publish/Makefile
index 64486a5e1..fd3a62ed6 100644
--- a/test/cbmc/proofs/MQTT_Publish/Makefile
+++ b/test/cbmc/proofs/MQTT_Publish/Makefile
@@ -29,6 +29,8 @@ MAX_NETWORK_SEND_TRIES=3
 # Please see test/cbmc/include/core_mqtt_config.h for more
 # information.
 MQTT_STATE_ARRAY_MAX_COUNT=11
+PUBLISH_PACKET_VECTORS = 5
+
 DEFINES += -DMAX_NETWORK_SEND_TRIES=$(MAX_NETWORK_SEND_TRIES)
 INCLUDES +=
 
@@ -39,7 +41,7 @@ REMOVE_FUNCTION_BODY +=
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 # These loops will run for the maximum number of publishes pending acknowledgement.
 # This is set in test/cbmc/include/core_mqtt_config.h.
 UNWINDSET += __CPROVER_file_local_core_mqtt_state_c_addRecord.0:$(MQTT_STATE_ARRAY_MAX_COUNT)
@@ -48,6 +50,9 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_state_c_findInRecord.0:$(MQTT_STATE_
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_encodeRemainingLength.0:5
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${PUBLISH_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${PUBLISH_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${PUBLISH_PACKET_VECTORS}
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c

From 239bb3bd425739eed7386138c4f914c7a3b0d868 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 20:35:14 +0000
Subject: [PATCH 22/35] Update the function name

---
 test/cbmc/proofs/MQTT_Connect/Makefile     | 6 +++---
 test/cbmc/proofs/MQTT_Disconnect/Makefile  | 6 +++---
 test/cbmc/proofs/MQTT_Ping/Makefile        | 4 ++--
 test/cbmc/proofs/MQTT_ProcessLoop/Makefile | 6 +++---
 test/cbmc/proofs/MQTT_Publish/Makefile     | 4 ++--
 test/cbmc/proofs/MQTT_ReceiveLoop/Makefile | 6 +++---
 test/cbmc/proofs/MQTT_Unsubscribe/Makefile | 4 ++--
 7 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/test/cbmc/proofs/MQTT_Connect/Makefile b/test/cbmc/proofs/MQTT_Connect/Makefile
index 66e0df047..638467309 100644
--- a/test/cbmc/proofs/MQTT_Connect/Makefile
+++ b/test/cbmc/proofs/MQTT_Connect/Makefile
@@ -60,12 +60,12 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_c_recvExact.0:$(MAX_NETWORK_RECV_TRI
 # If the user passed in timeout is zero, then the loop will run until the
 # MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT is reached.
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_receiveConnack.0:$(MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT)
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 # The loops are unwound 5 times because these functions divides a size_t
 # variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
diff --git a/test/cbmc/proofs/MQTT_Disconnect/Makefile b/test/cbmc/proofs/MQTT_Disconnect/Makefile
index a63b90b09..351ad5b60 100644
--- a/test/cbmc/proofs/MQTT_Disconnect/Makefile
+++ b/test/cbmc/proofs/MQTT_Disconnect/Makefile
@@ -30,12 +30,12 @@ DEFINES += -DMAX_NETWORK_SEND_TRIES=$(MAX_NETWORK_SEND_TRIES)
 INCLUDES +=
 
 REMOVE_FUNCTION_BODY +=
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c
diff --git a/test/cbmc/proofs/MQTT_Ping/Makefile b/test/cbmc/proofs/MQTT_Ping/Makefile
index c0024f4fa..ea36f2c74 100644
--- a/test/cbmc/proofs/MQTT_Ping/Makefile
+++ b/test/cbmc/proofs/MQTT_Ping/Makefile
@@ -29,8 +29,8 @@ MAX_NETWORK_SEND_TRIES=3
 DEFINES += -DMAX_NETWORK_SEND_TRIES=$(MAX_NETWORK_SEND_TRIES)
 INCLUDES +=
 
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # test/cbmc/stubs/network_interface_stubs.c for more
 # information.
diff --git a/test/cbmc/proofs/MQTT_ProcessLoop/Makefile b/test/cbmc/proofs/MQTT_ProcessLoop/Makefile
index bfb14f7e4..b1f72d17d 100644
--- a/test/cbmc/proofs/MQTT_ProcessLoop/Makefile
+++ b/test/cbmc/proofs/MQTT_ProcessLoop/Makefile
@@ -52,12 +52,12 @@ REMOVE_FUNCTION_BODY += memmove # Use stub
 
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_discardStoredPacket.0:$(MAX_NETWORK_RECV_TRIES)
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_recvExact.0:$(MAX_NETWORK_RECV_TRIES)
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 # The getRemainingLength loop is unwound 5 times because getRemainingLength()
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
diff --git a/test/cbmc/proofs/MQTT_Publish/Makefile b/test/cbmc/proofs/MQTT_Publish/Makefile
index fd3a62ed6..ddbf5042c 100644
--- a/test/cbmc/proofs/MQTT_Publish/Makefile
+++ b/test/cbmc/proofs/MQTT_Publish/Makefile
@@ -36,8 +36,8 @@ INCLUDES +=
 
 REMOVE_FUNCTION_BODY +=
 REMOVE_FUNCTION_BODY +=
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
diff --git a/test/cbmc/proofs/MQTT_ReceiveLoop/Makefile b/test/cbmc/proofs/MQTT_ReceiveLoop/Makefile
index d8778405d..0a161df95 100644
--- a/test/cbmc/proofs/MQTT_ReceiveLoop/Makefile
+++ b/test/cbmc/proofs/MQTT_ReceiveLoop/Makefile
@@ -34,12 +34,12 @@ REMOVE_FUNCTION_BODY += memmove # Use stub
 # The loops below are unwound once more than the exclusive timeout bound.
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_discardStoredPacket.0:$(MAX_NETWORK_RECV_TRIES)
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_recvExact.0:$(MAX_NETWORK_RECV_TRIES)
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendPacket.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 # The getRemainingLength loop is unwound 5 times because getRemainingLength()
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
diff --git a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
index b944a90af..7832f8db4 100644
--- a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
+++ b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
@@ -37,8 +37,8 @@ DEFINES += -DSUBSCRIPTION_COUNT_MAX=$(SUBSCRIPTION_COUNT_MAX)
 INCLUDES +=
 
 REMOVE_FUNCTION_BODY +=
-# Unlike recvExact, sendPacket is not bounded by the timeout. The loop in
-# sendPacket will continue until all the bytes are sent or a network error
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
 # occurs. Please see NetworkInterfaceReceiveStub in
 # libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
 # information.

From 3fdcf82b054c4a1d546488719f2d2daf2901a532 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 22:10:26 +0000
Subject: [PATCH 23/35] Fix more CBMC proofs

---
 source/core_mqtt.c                         | 12 ++++--------
 test/cbmc/proofs/MQTT_Connect/Makefile     |  4 ++++
 test/cbmc/proofs/MQTT_Unsubscribe/Makefile |  6 +++---
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index c4b154d80..5f7daaa99 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -1844,14 +1844,14 @@ static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
     MQTTStatus_t status = MQTTSuccess;
     uint8_t unsubscribeheader[ 7 ];
     uint8_t * pIndex;
-    TransportOutVector_t pIoVector[ 4 ];
+    TransportOutVector_t pIoVector[ 3 ];
     TransportOutVector_t * pIterator;
     uint8_t serializedTopicFieldLength[ 2 ];
     size_t totalPacketLength = 0U;
 
-    /* Subscribe packet always has 4 vector fields. Namely:
-     * Header + Topic Filter length + Topic filter + QoS */
-    const size_t ioVectorLength = 4U;
+    /* Unsubscribe packet always has 3 vector fields. Namely:
+     * Header + Topic Filter length + Topic filter */
+    const size_t ioVectorLength = 3U;
 
     pIndex = unsubscribeheader;
     pIterator = pIoVector;
@@ -1873,10 +1873,6 @@ static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
                                           pIterator,
                                           &totalPacketLength );
 
-    /* Lastly, the QoS gets sent. */
-    pIterator->iov_base = &( pSubscription->qos );
-    pIterator->iov_len = 1U;
-
     if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
     {
         status = MQTTSendFailed;
diff --git a/test/cbmc/proofs/MQTT_Connect/Makefile b/test/cbmc/proofs/MQTT_Connect/Makefile
index 638467309..de2bb21f9 100644
--- a/test/cbmc/proofs/MQTT_Connect/Makefile
+++ b/test/cbmc/proofs/MQTT_Connect/Makefile
@@ -40,6 +40,7 @@ MAX_NETWORK_RECV_TRIES=4
 # information on these defines.
 MQTT_STATE_ARRAY_MAX_COUNT=11
 MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT=3
+CONNECT_PACKET_VECTORS = 12
 DEFINES += -DMQTT_RECEIVE_TIMEOUT=$(MQTT_RECEIVE_TIMEOUT)
 DEFINES += -DMAX_NETWORK_SEND_TRIES=$(MAX_NETWORK_SEND_TRIES)
 DEFINES += -DMAX_NETWORK_RECV_TRIES=$(MAX_NETWORK_RECV_TRIES)
@@ -75,6 +76,9 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_getRemainingLength.0:5
 # acknowledgements plus one. This value is set in
 # test/cbmc/include/core_mqtt_config.h.
 UNWINDSET += __CPROVER_file_local_core_mqtt_state_c_stateSelect.0:$(MQTT_STATE_ARRAY_MAX_COUNT)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${CONNECT_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${CONNECT_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${CONNECT_PACKET_VECTORS}
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c
diff --git a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
index 7832f8db4..941740681 100644
--- a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
+++ b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
@@ -46,9 +46,9 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TR
 UNWINDSET += allocateMqttSubscriptionList.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_calculateSubscriptionPacketSize.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += MQTT_SerializeUnsubscribe.0:$(SUBSCRIPTION_COUNT_MAX)
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${SUBSCRIBE_PACKET_VECTORS}
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${SUBSCRIBE_PACKET_VECTORS}
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${SUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${UNSUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${UNSUBSCRIBE_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${UNSUBSCRIBE_PACKET_VECTORS}
 # The encodeRemainingLength loop is unwound 5 times because encodeRemainingLength()
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...

From c5ece552344a0168b3d9e7838a0c80e38e927367 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 23:02:20 +0000
Subject: [PATCH 24/35] Fix MQTT Connect proof

---
 source/core_mqtt.c                                   |  4 ++--
 test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c |  1 +
 test/cbmc/proofs/MQTT_Connect/Makefile               | 11 ++---------
 3 files changed, 5 insertions(+), 11 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 5f7daaa99..e4840fa11 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -796,8 +796,8 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
             break;
         }
 
-        while( ( bytesSentThisVector >= pIoVectIterator->iov_len ) &&
-               ( pIoVectIterator < &( pIoVec[ ioVecCount ] ) ) )
+        while( ( pIoVectIterator < &( pIoVec[ ioVecCount ] ) ) &&
+               ( bytesSentThisVector >= pIoVectIterator->iov_len ) )
         {
             bytesSentThisVector -= pIoVectIterator->iov_len;
             pIoVectIterator++;
diff --git a/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c b/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
index 12873a787..0db69feb4 100644
--- a/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
+++ b/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
@@ -37,6 +37,7 @@ void harness()
 
     pContext = allocateMqttContext( NULL );
     __CPROVER_assume( isValidMqttContext( pContext ) );
+    __CPROVER_assume( pContext->networkBuffer.pBuffer != NULL );
 
     pConnectInfo = allocateMqttConnectInfo( NULL );
     __CPROVER_assume( isValidMqttConnectInfo( pConnectInfo ) );
diff --git a/test/cbmc/proofs/MQTT_Connect/Makefile b/test/cbmc/proofs/MQTT_Connect/Makefile
index de2bb21f9..1082e2e98 100644
--- a/test/cbmc/proofs/MQTT_Connect/Makefile
+++ b/test/cbmc/proofs/MQTT_Connect/Makefile
@@ -53,6 +53,8 @@ REMOVE_FUNCTION_BODY += MQTT_ProcessLoop
 REMOVE_FUNCTION_BODY += MQTT_ReceiveLoop
 REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_handleIncomingPublish
 REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_handleKeepAlive
+REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_sendMessageVector
+REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_sendBuffer
 
 # The loop below is unwound once more than the timeout. The loop below uses
 # the user passed in timeout to break the loop.
@@ -61,12 +63,6 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_c_recvExact.0:$(MAX_NETWORK_RECV_TRI
 # If the user passed in timeout is zero, then the loop will run until the
 # MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT is reached.
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_receiveConnack.0:$(MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT)
-# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
-# sendBuffer will continue until all the bytes are sent or a network error
-# occurs. Please see NetworkInterfaceReceiveStub in
-# libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
-# information.
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 # The loops are unwound 5 times because these functions divides a size_t
 # variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
@@ -76,9 +72,6 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_getRemainingLength.0:5
 # acknowledgements plus one. This value is set in
 # test/cbmc/include/core_mqtt_config.h.
 UNWINDSET += __CPROVER_file_local_core_mqtt_state_c_stateSelect.0:$(MQTT_STATE_ARRAY_MAX_COUNT)
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${CONNECT_PACKET_VECTORS}
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${CONNECT_PACKET_VECTORS}
-UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${CONNECT_PACKET_VECTORS}
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c

From 1b3992a91090b05700507b653f332f8193ec5c17 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Thu, 25 Aug 2022 23:31:18 +0000
Subject: [PATCH 25/35] Add unwinding loops

---
 test/cbmc/proofs/MQTT_Connect/Makefile | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/test/cbmc/proofs/MQTT_Connect/Makefile b/test/cbmc/proofs/MQTT_Connect/Makefile
index 1082e2e98..9a0153277 100644
--- a/test/cbmc/proofs/MQTT_Connect/Makefile
+++ b/test/cbmc/proofs/MQTT_Connect/Makefile
@@ -63,6 +63,12 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_c_recvExact.0:$(MAX_NETWORK_RECV_TRI
 # If the user passed in timeout is zero, then the loop will run until the
 # MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT is reached.
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_receiveConnack.0:$(MQTT_MAX_CONNACK_RECEIVE_RETRY_COUNT)
+# Unlike recvExact, sendBuffer is not bounded by the timeout. The loop in
+# sendBuffer will continue until all the bytes are sent or a network error
+# occurs. Please see NetworkInterfaceReceiveStub in
+# libraries\standard\mqtt\cbmc\stubs\network_interface_stubs.c for more
+# information.
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 # The loops are unwound 5 times because these functions divides a size_t
 # variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
@@ -72,6 +78,9 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_getRemainingLength.0:5
 # acknowledgements plus one. This value is set in
 # test/cbmc/include/core_mqtt_config.h.
 UNWINDSET += __CPROVER_file_local_core_mqtt_state_c_stateSelect.0:$(MQTT_STATE_ARRAY_MAX_COUNT)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${CONNECT_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${CONNECT_PACKET_VECTORS}
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${CONNECT_PACKET_VECTORS}
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c

From d22ec5854f337e1cc35cfd60bb64d4842dc7cad6 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Fri, 26 Aug 2022 06:42:07 +0000
Subject: [PATCH 26/35] Fix last CBMC proof

---
 source/core_mqtt.c                            |  4 ++-
 .../MQTT_Connect/MQTT_Connect_harness.c       | 26 +++++++++++++++++++
 test/cbmc/proofs/MQTT_Connect/Makefile        |  4 +--
 3 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index e4840fa11..5c2286c92 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -745,6 +745,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
     uint32_t timeoutTime;
     uint32_t bytesToSend = 0U;
     int32_t bytesSentOrError = 0U;
+    uint64_t temp = 0;
     TransportOutVector_t * pIoVectIterator;
     size_t vectorsToBeSent = ioVecCount;
 
@@ -759,6 +760,7 @@ static int32_t sendMessageVector( MQTTContext_t * pContext,
     /* Count the total number of bytes to be sent as outlined in the vector. */
     for( pIoVectIterator = pIoVec; pIoVectIterator < &( pIoVec[ ioVecCount ] ); pIoVectIterator++ )
     {
+        temp += pIoVectIterator->iov_len;
         bytesToSend += pIoVectIterator->iov_len;
     }
 
@@ -2061,7 +2063,7 @@ static MQTTStatus_t sendConnectWithoutCopy( MQTTContext_t * pContext,
                                serializedUsernameLength,
                                serializedPasswordLength );
 
-        ioVectorLength = ( size_t ) ( ( iterator - pIoVector ) + 1 );
+        ioVectorLength = ( size_t ) ( iterator - pIoVector );
 
         bytesSentOrError = sendMessageVector( pContext, pIoVector, ioVectorLength );
 
diff --git a/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c b/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
index 0db69feb4..ddf290f4b 100644
--- a/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
+++ b/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
@@ -33,17 +33,43 @@ void harness()
     MQTTConnectInfo_t * pConnectInfo;
     MQTTPublishInfo_t * pWillInfo;
     uint32_t timeoutMs;
+    size_t totalMessageLength = 0U;
     bool * pSessionPresent;
 
     pContext = allocateMqttContext( NULL );
     __CPROVER_assume( isValidMqttContext( pContext ) );
+    __CPROVER_assume( pContext != NULL );
     __CPROVER_assume( pContext->networkBuffer.pBuffer != NULL );
 
     pConnectInfo = allocateMqttConnectInfo( NULL );
     __CPROVER_assume( isValidMqttConnectInfo( pConnectInfo ) );
 
+    if( pConnectInfo != NULL )
+    {
+        /* 128^4 is the length imposed by the MQTT spec. */
+        __CPROVER_assume( pConnectInfo->passwordLength < 268435456 );
+        __CPROVER_assume( pConnectInfo->userNameLength < 268435456 );
+        __CPROVER_assume( pConnectInfo->clientIdentifierLength < 268435456 );
+
+        totalMessageLength += pConnectInfo->passwordLength;
+        totalMessageLength += pConnectInfo->userNameLength;
+        totalMessageLength += pConnectInfo->clientIdentifierLength;
+    }
+
     pWillInfo = allocateMqttPublishInfo( NULL );
     __CPROVER_assume( isValidMqttPublishInfo( pWillInfo ) );
+    if( pWillInfo != NULL )
+    {
+        /* 128^4 is the length imposed by the MQTT spec. */
+        __CPROVER_assume( pWillInfo->topicNameLength < 268435456 );
+        __CPROVER_assume( pWillInfo->payloadLength < 268435456 );
+
+        totalMessageLength += pWillInfo->topicNameLength;
+        totalMessageLength += pWillInfo->payloadLength;
+    }
+
+    /* 128^4 is the length imposed by the MQTT spec. */
+    __CPROVER_assume( totalMessageLength <= 268435456 );
 
     pSessionPresent = malloc( sizeof( bool ) );
 
diff --git a/test/cbmc/proofs/MQTT_Connect/Makefile b/test/cbmc/proofs/MQTT_Connect/Makefile
index 9a0153277..13ae71f3e 100644
--- a/test/cbmc/proofs/MQTT_Connect/Makefile
+++ b/test/cbmc/proofs/MQTT_Connect/Makefile
@@ -53,8 +53,8 @@ REMOVE_FUNCTION_BODY += MQTT_ProcessLoop
 REMOVE_FUNCTION_BODY += MQTT_ReceiveLoop
 REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_handleIncomingPublish
 REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_handleKeepAlive
-REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_sendMessageVector
-REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_sendBuffer
+#REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_sendMessageVector
+#REMOVE_FUNCTION_BODY += __CPROVER_file_local_core_mqtt_c_sendBuffer
 
 # The loop below is unwound once more than the timeout. The loop below uses
 # the user passed in timeout to break the loop.

From 2ea953aec1f3b9cf6ae1cfc0957fe3d3b71af3e1 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Fri, 26 Aug 2022 06:59:25 +0000
Subject: [PATCH 27/35] Fix formatting

---
 test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c b/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
index ddf290f4b..c4bcd3493 100644
--- a/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
+++ b/test/cbmc/proofs/MQTT_Connect/MQTT_Connect_harness.c
@@ -58,6 +58,7 @@ void harness()
 
     pWillInfo = allocateMqttPublishInfo( NULL );
     __CPROVER_assume( isValidMqttPublishInfo( pWillInfo ) );
+
     if( pWillInfo != NULL )
     {
         /* 128^4 is the length imposed by the MQTT spec. */

From 624cd41a25cfabe3b06437138fe0497ec29fffab Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Fri, 26 Aug 2022 17:15:39 -0700
Subject: [PATCH 28/35] Update the Subscribe and Unsubscribe functions

---
 source/core_mqtt.c         | 154 ++++++++++++++++++++++++++-----------
 source/include/core_mqtt.h |  54 +++++++------
 2 files changed, 138 insertions(+), 70 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 5c2286c92..9eacf5318 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -31,6 +31,7 @@
 #include "core_mqtt_state.h"
 #include "core_mqtt_default_logging.h"
 
+#define MQTT_SUB_UNSUB_MAX_VECTORS             ( 4U )
 /*-----------------------------------------------------------*/
 
 /**
@@ -163,7 +164,8 @@ static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
  * @return #MQTTSuccess or #MQTTSendFailed.
  */
 static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
-                                              const MQTTSubscribeInfo_t * pSubscription,
+                                              const MQTTSubscribeInfo_t * pSubscriptionList,
+                                              size_t subscriptionCount,
                                               uint16_t packetId,
                                               size_t remainingLength );
 
@@ -179,7 +181,8 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
  * @return #MQTTSuccess or #MQTTSendFailed.
  */
 static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
-                                                const MQTTSubscribeInfo_t * pSubscription,
+                                                const MQTTSubscribeInfo_t * pSubscriptionList,
+                                                size_t subscriptionCount,
                                                 uint16_t packetId,
                                                 size_t remainingLength );
 
@@ -1788,21 +1791,26 @@ static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength
 /*-----------------------------------------------------------*/
 
 static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
-                                              const MQTTSubscribeInfo_t * pSubscription,
+                                              const MQTTSubscribeInfo_t * pSubscriptionList,
+                                              size_t subscriptionCount,
                                               uint16_t packetId,
                                               size_t remainingLength )
 {
     MQTTStatus_t status = MQTTSuccess;
     uint8_t subscribeheader[ 7 ];
     uint8_t * pIndex;
-    TransportOutVector_t pIoVector[ 4 ];
+    TransportOutVector_t pIoVector[ MQTT_SUB_UNSUB_MAX_VECTORS ];
     TransportOutVector_t * pIterator;
     uint8_t serializedTopicFieldLength[ 2 ];
     size_t totalPacketLength = 0U;
+    size_t ioVectorLength = 0U;
+    size_t subscriptionsSent = 0U;
+    /* For subscribe, only three vector slots are required per topic string. */
+    const size_t subscriptionStringVectorSlots = 3U;
 
-    /* Subscribe packet always has 4 vector fields. Namely:
-     * Header + Topic Filter length + Topic filter + QoS */
-    const size_t ioVectorLength = 4U;
+    /* The vector array should be at least three element long as the topic
+     * string needs these many vector elements to be stored. */
+    assert( MQTT_SUB_UNSUB_MAX_VECTORS >= subscriptionStringVectorSlots );
 
     pIndex = subscribeheader;
     pIterator = pIoVector;
@@ -1815,22 +1823,45 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
     pIterator->iov_base = subscribeheader;
     pIterator->iov_len = ( size_t ) ( pIndex - subscribeheader );
     pIterator++;
+    ioVectorLength++;
     totalPacketLength += ( size_t ) ( pIndex - subscribeheader );
 
-    /* The topic filter gets sent next. */
-    pIterator = addEncodedStringToVector( serializedTopicFieldLength,
-                                          pSubscription->pTopicFilter,
-                                          pSubscription->topicFilterLength,
-                                          pIterator,
-                                          &totalPacketLength );
+    while( ( status == MQTTSuccess ) && ( subscriptionsSent < subscriptionCount ) )
+    {
+        /* Check whether the subscription topic (with QoS) will fit in the
+         * given vector. */
+        while( ( ioVectorLength <= ( MQTT_SUB_UNSUB_MAX_VECTORS - subscriptionStringVectorSlots ) ) &&
+               ( subscriptionsSent < subscriptionCount ) )
+        {
+            /* The topic filter gets sent next. */
+            pIterator = addEncodedStringToVector( serializedTopicFieldLength,
+                                                  pSubscriptionList[ subscriptionsSent ].pTopicFilter,
+                                                  pSubscriptionList[ subscriptionsSent ].topicFilterLength,
+                                                  pIterator,
+                                                  &totalPacketLength );
 
-    /* Lastly, the QoS gets sent. */
-    pIterator->iov_base = &( pSubscription->qos );
-    pIterator->iov_len = 1U;
+            /* Lastly, the QoS gets sent. */
+            pIterator->iov_base = &( pSubscriptionList[ subscriptionsSent ].qos);
+            pIterator->iov_len = 1U;
 
-    if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
-    {
-        status = MQTTSendFailed;
+            /* Two slots get used by the topic string length and topic string. And
+             * one slot gets used by the quality of service. */
+            ioVectorLength += subscriptionStringVectorSlots;
+
+            subscriptionsSent++;
+        }
+
+        if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
+        {
+            status = MQTTSendFailed;
+        }
+
+        /* Update the iterator for the next potential loop iteration. */
+        pIterator = pIoVector;
+        /* Reset the vector length for the next potential loop iteration. */
+        ioVectorLength = 0U;
+        /* Reset the packet length for the next potential loop iteration. */
+        totalPacketLength = 0U;
     }
 
     return status;
@@ -1839,21 +1870,26 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
 /*-----------------------------------------------------------*/
 
 static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
-                                                const MQTTSubscribeInfo_t * pSubscription,
+                                                const MQTTSubscribeInfo_t * pSubscriptionList,
+                                                size_t subscriptionCount,
                                                 uint16_t packetId,
                                                 size_t remainingLength )
 {
     MQTTStatus_t status = MQTTSuccess;
     uint8_t unsubscribeheader[ 7 ];
     uint8_t * pIndex;
-    TransportOutVector_t pIoVector[ 3 ];
+    TransportOutVector_t pIoVector[ MQTT_SUB_UNSUB_MAX_VECTORS ];
     TransportOutVector_t * pIterator;
     uint8_t serializedTopicFieldLength[ 2 ];
     size_t totalPacketLength = 0U;
+    size_t unsubscriptionsSent = 0U;
+    size_t ioVectorLength = 0U;
+    /* For unsubscribe, only two vector slots are required per topic string. */
+    const size_t subscriptionStringVectorSlots = 2U;
 
-    /* Unsubscribe packet always has 3 vector fields. Namely:
-     * Header + Topic Filter length + Topic filter */
-    const size_t ioVectorLength = 3U;
+    /* The vector array should be at least three element long as the topic
+     * string needs these many vector elements to be stored. */
+    assert( MQTT_SUB_UNSUB_MAX_VECTORS >= subscriptionStringVectorSlots );
 
     pIndex = unsubscribeheader;
     pIterator = pIoVector;
@@ -1865,19 +1901,41 @@ static MQTTStatus_t sendUnsubscribeWithoutCopy( MQTTContext_t * pContext,
     /* The header is to be sent first. */
     pIterator->iov_base = unsubscribeheader;
     pIterator->iov_len = ( size_t ) ( pIndex - unsubscribeheader );
-    pIterator++;
     totalPacketLength += ( size_t ) ( pIndex - unsubscribeheader );
+    pIterator++;
+    ioVectorLength++;
 
-    /* The topic filter gets sent next. */
-    pIterator = addEncodedStringToVector( serializedTopicFieldLength,
-                                          pSubscription->pTopicFilter,
-                                          pSubscription->topicFilterLength,
-                                          pIterator,
-                                          &totalPacketLength );
-
-    if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
+    while( ( status == MQTTSuccess ) && ( unsubscriptionsSent < subscriptionCount ) )
     {
-        status = MQTTSendFailed;
+        /* Check whether the subscription topic will fit in the given vector. */
+        while( ( ioVectorLength <= ( MQTT_SUB_UNSUB_MAX_VECTORS - subscriptionStringVectorSlots ) ) &&
+               ( unsubscriptionsSent < subscriptionCount ) )
+        {
+            /* The topic filter gets sent next. */
+            pIterator = addEncodedStringToVector( serializedTopicFieldLength,
+                                                  pSubscriptionList[ unsubscriptionsSent ].pTopicFilter,
+                                                  pSubscriptionList[ unsubscriptionsSent ].topicFilterLength,
+                                                  pIterator,
+                                                  &totalPacketLength );
+
+            /* Two slots get used by the topic string length and topic string. And
+             * one slot gets used by the quality of service. */
+            ioVectorLength += subscriptionStringVectorSlots;
+
+            unsubscriptionsSent++;
+        }
+
+        if( sendMessageVector( pContext, pIoVector, ioVectorLength ) != ( int32_t ) totalPacketLength )
+        {
+            status = MQTTSendFailed;
+        }
+
+        /* Update the iterator for the next potential loop iteration. */
+        pIterator = pIoVector;
+        /* Reset the vector length for the next potential loop iteration. */
+        ioVectorLength = 0U;
+        /* Reset the packet length for the next potential loop iteration. */
+        totalPacketLength = 0U;
     }
 
     return status;
@@ -2468,22 +2526,23 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
 /*-----------------------------------------------------------*/
 
 MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
-                             const MQTTSubscribeInfo_t * pSubscription,
+                             const MQTTSubscribeInfo_t * pSubscriptionList,
+                             size_t subscriptionCount,
                              uint16_t packetId )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
 
     /* Validate arguments. */
     MQTTStatus_t status = validateSubscribeUnsubscribeParams( pContext,
-                                                              pSubscription,
-                                                              1U,
+                                                              pSubscriptionList,
+                                                              subscriptionCount,
                                                               packetId );
 
     if( status == MQTTSuccess )
     {
         /* Get the remaining length and packet size.*/
-        status = MQTT_GetSubscribePacketSize( pSubscription,
-                                              1U,
+        status = MQTT_GetSubscribePacketSize( pSubscriptionList,
+                                              subscriptionCount,
                                               &remainingLength,
                                               &packetSize );
         LogDebug( ( "SUBSCRIBE packet size is %lu and remaining length is %lu.",
@@ -2495,7 +2554,8 @@ MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
     {
         /* Send MQTT SUBSCRIBE packet. */
         status = sendSubscribeWithoutCopy( pContext,
-                                           pSubscription,
+                                           pSubscriptionList,
+                                           subscriptionCount,
                                            packetId,
                                            remainingLength );
     }
@@ -2663,22 +2723,23 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
 /*-----------------------------------------------------------*/
 
 MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
-                               const MQTTSubscribeInfo_t * pSubscription,
+                               const MQTTSubscribeInfo_t * pSubscriptionList,
+                               size_t subscriptionCount,
                                uint16_t packetId )
 {
     size_t remainingLength = 0UL, packetSize = 0UL;
 
     /* Validate arguments. */
     MQTTStatus_t status = validateSubscribeUnsubscribeParams( pContext,
-                                                              pSubscription,
-                                                              1U,
+                                                              pSubscriptionList,
+                                                              subscriptionCount,
                                                               packetId );
 
     if( status == MQTTSuccess )
     {
         /* Get the remaining length and packet size.*/
-        status = MQTT_GetUnsubscribePacketSize( pSubscription,
-                                                1U,
+        status = MQTT_GetUnsubscribePacketSize( pSubscriptionList,
+                                                subscriptionCount,
                                                 &remainingLength,
                                                 &packetSize );
         LogDebug( ( "UNSUBSCRIBE packet size is %lu and remaining length is %lu.",
@@ -2689,7 +2750,8 @@ MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
     if( status == MQTTSuccess )
     {
         status = sendUnsubscribeWithoutCopy( pContext,
-                                             pSubscription,
+                                             pSubscriptionList,
+                                             subscriptionCount,
                                              packetId,
                                              remainingLength );
     }
diff --git a/source/include/core_mqtt.h b/source/include/core_mqtt.h
index 97b2248ae..d13f75c0d 100644
--- a/source/include/core_mqtt.h
+++ b/source/include/core_mqtt.h
@@ -430,10 +430,12 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
 /* @[declare_mqtt_connect] */
 
 /**
- * @brief Sends MQTT SUBSCRIBE for the given topic filter to the broker.
+ * @brief Sends MQTT SUBSCRIBE for the given list of topic filters to
+ * the broker.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pSubscription MQTT subscription info.
+ * @param[in] pSubscriptionList List of MQTT subscription info.
+ * @param[in] subscriptionCount The number of elements in pSubscriptionList.
  * @param[in] packetId Packet ID generated by #MQTT_GetPacketId.
  *
  * @return #MQTTNoMemory if the #MQTTContext_t.networkBuffer is too small to
@@ -454,31 +456,32 @@ MQTTStatus_t MQTT_Connect( MQTTContext_t * pContext,
  * // This is assumed to be a list of filters we want to subscribe to.
  * const char * filters[ NUMBER_OF_SUBSCRIPTIONS ];
  *
- * // Subscribe to each subscription filter.
+ * // Set each subscription.
  * for( int i = 0; i < NUMBER_OF_SUBSCRIPTIONS; i++ )
  * {
  *      subscriptionList[ i ].qos = MQTTQoS0;
  *      // Each subscription needs a topic filter.
  *      subscriptionList[ i ].pTopicFilter = filters[ i ];
  *      subscriptionList[ i ].topicFilterLength = strlen( filters[ i ] );
+ * }
  *
- *      // Obtain a new packet id for the subscription.
- *      packetId = MQTT_GetPacketId( pContext );
+ * // Obtain a new packet id for the subscription.
+ * packetId = MQTT_GetPacketId( pContext );
  *
- *      status = MQTT_Subscribe( pContext, &subscriptionList[ i ], packetId );
+ * status = MQTT_Subscribe( pContext, &subscriptionList[ 0 ], NUMBER_OF_SUBSCRIPTIONS, packetId );
  *
- *      if( status == MQTTSuccess )
- *      {
- *           // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the SUBACK.
- *           // If the broker accepts the subscription we can now receive publishes
- *           // on the requested topics.
- *      }
+ * if( status == MQTTSuccess )
+ * {
+ *      // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the SUBACK.
+ *      // If the broker accepts the subscription we can now receive publishes
+ *      // on the requested topics.
  * }
  * @endcode
  */
 /* @[declare_mqtt_subscribe] */
 MQTTStatus_t MQTT_Subscribe( MQTTContext_t * pContext,
-                             const MQTTSubscribeInfo_t * pSubscription,
+                             const MQTTSubscribeInfo_t * pSubscriptionList,
+                             size_t subscriptionCount,
                              uint16_t packetId );
 /* @[declare_mqtt_subscribe] */
 
@@ -559,10 +562,12 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
 /* @[declare_mqtt_ping] */
 
 /**
- * @brief Sends MQTT UNSUBSCRIBE for the topic filter to the broker.
+ * @brief Sends MQTT UNSUBSCRIBE for the given list of topic filters to
+ * the broker.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pSubscription MQTT subscription info.
+ * @param[in] pSubscriptionList List of MQTT subscription info.
+ * @param[in] subscriptionCount The number of elements in pSubscriptionList.
  * @param[in] packetId packet ID generated by #MQTT_GetPacketId.
  *
  * @return #MQTTNoMemory if the #MQTTContext_t.networkBuffer is too small to
@@ -590,23 +595,24 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext );
  *      unsubscribeList[ i ].topicFilterLength = strlen( filters[ i ] );
  *
  *      // The QoS field of MQTT_SubscribeInfo_t is unused for unsubscribing.
+ * }
  *
- *      // Obtain a new packet id for the unsubscribe request.
- *      packetId = MQTT_GetPacketId( pContext );
+ * // Obtain a new packet id for the unsubscribe request.
+ * packetId = MQTT_GetPacketId( pContext );
  *
- *      status = MQTT_Unsubscribe( pContext, &unsubscribeList[ i ], packetId );
+ * status = MQTT_Unsubscribe( pContext, &unsubscribeList[ 0 ], NUMBER_OF_SUBSCRIPTIONS, packetId );
  *
- *      if( status == MQTTSuccess )
- *      {
- *           // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the UNSUBACK.
- *           // After this the broker should no longer send publishes for these topics.
- *      }
+ * if( status == MQTTSuccess )
+ * {
+ *      // We must now call MQTT_ReceiveLoop() or MQTT_ProcessLoop() to receive the UNSUBACK.
+ *      // After this the broker should no longer send publishes for these topics.
  * }
  * @endcode
  */
 /* @[declare_mqtt_unsubscribe] */
 MQTTStatus_t MQTT_Unsubscribe( MQTTContext_t * pContext,
-                               const MQTTSubscribeInfo_t * pSubscription,
+                               const MQTTSubscribeInfo_t * pSubscriptionList,
+                               size_t subscriptionCount,
                                uint16_t packetId );
 /* @[declare_mqtt_unsubscribe] */
 

From f96b742746347571e6bd621b7562fac4b1354719 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Sat, 27 Aug 2022 00:42:15 +0000
Subject: [PATCH 29/35] Fix formatting and doxygen checks

---
 source/core_mqtt.c         | 9 +++++----
 source/include/core_mqtt.h | 8 +++++++-
 2 files changed, 12 insertions(+), 5 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 9eacf5318..d461cf357 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -31,7 +31,6 @@
 #include "core_mqtt_state.h"
 #include "core_mqtt_default_logging.h"
 
-#define MQTT_SUB_UNSUB_MAX_VECTORS             ( 4U )
 /*-----------------------------------------------------------*/
 
 /**
@@ -157,7 +156,8 @@ static void addWillAndConnectInfo( const MQTTConnectInfo_t * pConnectInfo,
  * directly sending it.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pSubscription MQTT subscription info.
+ * @param[in] pSubscriptionList List of MQTT subscription info.
+ * @param[in] subscriptionCount The count of elements in the list.
  * @param[in] packetId The packet ID of the subscribe packet
  * @param[in] remainingLength The remaining length of the subscribe packet.
  *
@@ -174,7 +174,8 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
  * directly sending it.
  *
  * @param[in] pContext Initialized MQTT context.
- * @param[in] pSubscription MQTT subscription info.
+ * @param[in] pSubscriptionList MQTT subscription info.
+ * @param[in] subscriptionCount The count of elements in the list.
  * @param[in] packetId The packet ID of the unsubscribe packet.
  * @param[in] remainingLength The remaining length of the unsubscribe packet.
  *
@@ -1841,7 +1842,7 @@ static MQTTStatus_t sendSubscribeWithoutCopy( MQTTContext_t * pContext,
                                                   &totalPacketLength );
 
             /* Lastly, the QoS gets sent. */
-            pIterator->iov_base = &( pSubscriptionList[ subscriptionsSent ].qos);
+            pIterator->iov_base = &( pSubscriptionList[ subscriptionsSent ].qos );
             pIterator->iov_len = 1U;
 
             /* Two slots get used by the topic string length and topic string. And
diff --git a/source/include/core_mqtt.h b/source/include/core_mqtt.h
index d13f75c0d..09b0e4c18 100644
--- a/source/include/core_mqtt.h
+++ b/source/include/core_mqtt.h
@@ -58,13 +58,19 @@
 #define MQTT_LIBRARY_VERSION    "v1.2.0"
 /** @endcond */
 
+/**
+ * @ingroup mqtt_constants
+ * @brief Maximum number of vectors in subscribe and unsubscribe packet.
+ */
+#define MQTT_SUB_UNSUB_MAX_VECTORS    ( 4U )
+
 /**
  * @ingroup mqtt_constants
  * @brief Invalid packet identifier.
  *
  * Zero is an invalid packet identifier as per MQTT v3.1.1 spec.
  */
-#define MQTT_PACKET_ID_INVALID    ( ( uint16_t ) 0U )
+#define MQTT_PACKET_ID_INVALID        ( ( uint16_t ) 0U )
 
 /* Structures defined in this file. */
 struct MQTTPubAckInfo;

From ea3bd8a040428b54d5543a346cec0575037fd00b Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Sat, 27 Aug 2022 01:05:42 +0000
Subject: [PATCH 30/35] Fix broken CBMC proofs

---
 test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c    | 6 +++++-
 test/cbmc/proofs/MQTT_Subscribe/Makefile                    | 3 ++-
 .../cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c | 6 +++++-
 test/cbmc/proofs/MQTT_Unsubscribe/Makefile                  | 2 ++
 4 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c b/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c
index 2084be6cb..d3a0b2323 100644
--- a/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c
+++ b/test/cbmc/proofs/MQTT_Subscribe/MQTT_Subscribe_harness.c
@@ -37,8 +37,12 @@ void harness()
     pContext = allocateMqttContext( NULL );
     __CPROVER_assume( isValidMqttContext( pContext ) );
 
+    /* Please see the default bound description on SUBSCRIPTION_COUNT_MAX in
+     * mqtt_cbmc_state.c for more information. */
+    __CPROVER_assume( subscriptionCount < SUBSCRIPTION_COUNT_MAX );
+
     pSubscriptionList = allocateMqttSubscriptionList( NULL, 1U );
     __CPROVER_assume( isValidMqttSubscriptionList( pSubscriptionList, 1U ) );
 
-    MQTT_Subscribe( pContext, pSubscriptionList, packetId );
+    MQTT_Subscribe( pContext, pSubscriptionList, subscriptionCount, packetId );
 }
diff --git a/test/cbmc/proofs/MQTT_Subscribe/Makefile b/test/cbmc/proofs/MQTT_Subscribe/Makefile
index 53fbc3ce3..55b7afb4a 100644
--- a/test/cbmc/proofs/MQTT_Subscribe/Makefile
+++ b/test/cbmc/proofs/MQTT_Subscribe/Makefile
@@ -45,7 +45,6 @@ REMOVE_FUNCTION_BODY +=
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendBuffer.0:$(MAX_NETWORK_SEND_TRIES)
 UNWINDSET += allocateMqttSubscriptionList.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_calculateSubscriptionPacketSize.0:$(SUBSCRIPTION_COUNT_MAX)
-UNWINDSET += MQTT_SerializeSubscribe.0:$(SUBSCRIPTION_COUNT_MAX)
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.0:${SUBSCRIBE_PACKET_VECTORS}
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.1:${SUBSCRIBE_PACKET_VECTORS}
 UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${SUBSCRIBE_PACKET_VECTORS}
@@ -53,6 +52,8 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${SUBSCRIBE_PA
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_encodeRemainingLength.0:5
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendSubscribeWithoutCopy.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendSubscribeWithoutCopy.1:$(MAX_NETWORK_SEND_TRIES)
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c
diff --git a/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c b/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c
index 0fe1be53c..6a7f5671c 100644
--- a/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c
+++ b/test/cbmc/proofs/MQTT_Unsubscribe/MQTT_Unsubscribe_harness.c
@@ -37,8 +37,12 @@ void harness()
     pContext = allocateMqttContext( NULL );
     __CPROVER_assume( isValidMqttContext( pContext ) );
 
+    /* Please see the default bound description on SUBSCRIPTION_COUNT_MAX in
+     * mqtt_cbmc_state.c for more information. */
+    __CPROVER_assume( subscriptionCount < SUBSCRIPTION_COUNT_MAX );
+
     pSubscriptionList = allocateMqttSubscriptionList( NULL, 1U );
     __CPROVER_assume( isValidMqttSubscriptionList( pSubscriptionList, 1U ) );
 
-    MQTT_Unsubscribe( pContext, pSubscriptionList, packetId );
+    MQTT_Unsubscribe( pContext, pSubscriptionList, subscriptionCount, packetId );
 }
diff --git a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
index 941740681..5a3613fde 100644
--- a/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
+++ b/test/cbmc/proofs/MQTT_Unsubscribe/Makefile
@@ -53,6 +53,8 @@ UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendMessageVector.2:${UNSUBSCRIBE_
 # divides a size_t variable by 128 until it reaches zero to stop the loop.
 # log128(SIZE_MAX) = 4.571...
 UNWINDSET += __CPROVER_file_local_core_mqtt_serializer_c_encodeRemainingLength.0:5
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendUnsubscribeWithoutCopy.0:$(MAX_NETWORK_SEND_TRIES)
+UNWINDSET += __CPROVER_file_local_core_mqtt_c_sendUnsubscribeWithoutCopy.1:$(MAX_NETWORK_SEND_TRIES)
 
 PROOF_SOURCES += $(PROOFDIR)/$(HARNESS_FILE).c
 PROOF_SOURCES += $(SRCDIR)/test/cbmc/sources/mqtt_cbmc_state.c

From 78c6728ea30dd1972b263bc23ca2a60de7c698b7 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Sat, 27 Aug 2022 01:15:27 +0000
Subject: [PATCH 31/35] Fix memory statistic table

---
 docs/doxygen/include/size_table.md | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/docs/doxygen/include/size_table.md b/docs/doxygen/include/size_table.md
index cd80abff5..5997a82b7 100644
--- a/docs/doxygen/include/size_table.md
+++ b/docs/doxygen/include/size_table.md
@@ -9,8 +9,8 @@
     </tr>
     <tr>
         <td>core_mqtt.c</td>
-        <td><center>3.6K</center></td>
-        <td><center>3.1K</center></td>
+        <td><center>3.8K</center></td>
+        <td><center>3.2K</center></td>
     </tr>
     <tr>
         <td>core_mqtt_state.c</td>
@@ -24,7 +24,7 @@
     </tr>
     <tr>
         <td><b>Total estimates</b></td>
-        <td><b><center>7.9K</center></b></td>
-        <td><b><center>6.4K</center></b></td>
+        <td><b><center>8.1K</center></b></td>
+        <td><b><center>6.5K</center></b></td>
     </tr>
 </table>

From aa13564b52b63c3546217875d1a89003fba15e93 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Mon, 29 Aug 2022 13:24:11 -0700
Subject: [PATCH 32/35] Revert changes from serializer source

---
 source/core_mqtt.c                    |  14 ++--
 source/core_mqtt_serializer.c         | 111 ++++++++++++++++++++++++++
 source/include/core_mqtt_serializer.h | 110 -------------------------
 3 files changed, 118 insertions(+), 117 deletions(-)

diff --git a/source/core_mqtt.c b/source/core_mqtt.c
index 9eacf5318..74db3001b 100644
--- a/source/core_mqtt.c
+++ b/source/core_mqtt.c
@@ -1770,8 +1770,8 @@ static TransportOutVector_t * addEncodedStringToVector( uint8_t serailizedLength
     size_t packetLength = 0U;
     const size_t seralizedLengthFieldSize = 2U;
 
-    serailizedLength[ 0 ] = UINT16_HIGH_BYTE( length );
-    serailizedLength[ 1 ] = UINT16_LOW_BYTE( length );
+    serailizedLength[ 0 ] = ( ( uint8_t ) ( ( length ) >> 8 ) );
+    serailizedLength[ 1 ] = ( ( uint8_t ) ( ( length ) & 0x00ffU ) );
 
     iterator->iov_base = serailizedLength;
     iterator->iov_len = seralizedLengthFieldSize;
@@ -2657,11 +2657,11 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
     MQTTStatus_t status = MQTTSuccess;
     size_t packetSize = 0U;
     /* MQTT ping packets are of fixed length. */
-    uint8_t pingreqPacket[ MQTT_PACKET_PINGREQ_SIZE ];
+    uint8_t pingreqPacket[ 2U ];
     MQTTFixedBuffer_t localBuffer;
 
     localBuffer.pBuffer = pingreqPacket;
-    localBuffer.size = MQTT_PACKET_PINGREQ_SIZE;
+    localBuffer.size = 2U;
 
     if( pContext == NULL )
     {
@@ -2699,7 +2699,7 @@ MQTTStatus_t MQTT_Ping( MQTTContext_t * pContext )
          * from the user provided buffers. Thus it can be sent directly. */
         bytesSent = sendBuffer( pContext,
                                 localBuffer.pBuffer,
-                                MQTT_PACKET_PINGREQ_SIZE,
+                                2U,
                                 MQTT_SEND_RETRY_TIMEOUT_MS );
 
         /* It is an error to not send the entire PINGREQ packet. */
@@ -2767,10 +2767,10 @@ MQTTStatus_t MQTT_Disconnect( MQTTContext_t * pContext )
     int32_t bytesSent = 0;
     MQTTStatus_t status = MQTTSuccess;
     MQTTFixedBuffer_t localBuffer;
-    uint8_t disconnectPacket[ MQTT_DISCONNECT_PACKET_SIZE ];
+    uint8_t disconnectPacket[ 2U ];
 
     localBuffer.pBuffer = disconnectPacket;
-    localBuffer.size = MQTT_DISCONNECT_PACKET_SIZE;
+    localBuffer.size = 2U;
 
     /* Validate arguments. */
     if( pContext == NULL )
diff --git a/source/core_mqtt_serializer.c b/source/core_mqtt_serializer.c
index b553c1931..e2db56668 100644
--- a/source/core_mqtt_serializer.c
+++ b/source/core_mqtt_serializer.c
@@ -30,6 +30,117 @@
 #include "core_mqtt_serializer.h"
 #include "core_mqtt_default_logging.h"
 
+/**
+ * @brief MQTT protocol version 3.1.1.
+ */
+#define MQTT_VERSION_3_1_1                          ( ( uint8_t ) 4U )
+
+/**
+ * @brief Size of the fixed and variable header of a CONNECT packet.
+ */
+#define MQTT_PACKET_CONNECT_HEADER_SIZE             ( 10UL )
+
+/* MQTT CONNECT flags. */
+#define MQTT_CONNECT_FLAG_CLEAN                     ( 1 ) /**< @brief Clean session. */
+#define MQTT_CONNECT_FLAG_WILL                      ( 2 ) /**< @brief Will present. */
+#define MQTT_CONNECT_FLAG_WILL_QOS1                 ( 3 ) /**< @brief Will QoS 1. */
+#define MQTT_CONNECT_FLAG_WILL_QOS2                 ( 4 ) /**< @brief Will QoS 2. */
+#define MQTT_CONNECT_FLAG_WILL_RETAIN               ( 5 ) /**< @brief Will retain. */
+#define MQTT_CONNECT_FLAG_PASSWORD                  ( 6 ) /**< @brief Password present. */
+#define MQTT_CONNECT_FLAG_USERNAME                  ( 7 ) /**< @brief User name present. */
+
+/*
+ * Positions of each flag in the first byte of an MQTT PUBLISH packet's
+ * fixed header.
+ */
+#define MQTT_PUBLISH_FLAG_RETAIN                    ( 0 ) /**< @brief MQTT PUBLISH retain flag. */
+#define MQTT_PUBLISH_FLAG_QOS1                      ( 1 ) /**< @brief MQTT PUBLISH QoS1 flag. */
+#define MQTT_PUBLISH_FLAG_QOS2                      ( 2 ) /**< @brief MQTT PUBLISH QoS2 flag. */
+#define MQTT_PUBLISH_FLAG_DUP                       ( 3 ) /**< @brief MQTT PUBLISH duplicate flag. */
+
+/**
+ * @brief The size of MQTT DISCONNECT packets, per MQTT spec.
+ */
+#define MQTT_DISCONNECT_PACKET_SIZE                 ( 2UL )
+
+/**
+ * @brief A PINGREQ packet is always 2 bytes in size, defined by MQTT 3.1.1 spec.
+ */
+#define MQTT_PACKET_PINGREQ_SIZE                    ( 2UL )
+
+/**
+ * @brief The Remaining Length field of MQTT disconnect packets, per MQTT spec.
+ */
+#define MQTT_DISCONNECT_REMAINING_LENGTH            ( ( uint8_t ) 0 )
+
+/*
+ * Constants relating to CONNACK packets, defined by MQTT 3.1.1 spec.
+ */
+#define MQTT_PACKET_CONNACK_REMAINING_LENGTH        ( ( uint8_t ) 2U )    /**< @brief A CONNACK packet always has a "Remaining length" of 2. */
+#define MQTT_PACKET_CONNACK_SESSION_PRESENT_MASK    ( ( uint8_t ) 0x01U ) /**< @brief The "Session Present" bit is always the lowest bit. */
+
+/*
+ * UNSUBACK, PUBACK, PUBREC, PUBREL, and PUBCOMP always have a remaining length
+ * of 2.
+ */
+#define MQTT_PACKET_SIMPLE_ACK_REMAINING_LENGTH     ( ( uint8_t ) 2 ) /**< @brief PUBACK, PUBREC, PUBREl, PUBCOMP, UNSUBACK Remaining length. */
+#define MQTT_PACKET_PINGRESP_REMAINING_LENGTH       ( 0U )            /**< @brief A PINGRESP packet always has a "Remaining length" of 0. */
+
+/**
+ * @brief Per the MQTT 3.1.1 spec, the largest "Remaining Length" of an MQTT
+ * packet is this value, 256 MB.
+ */
+#define MQTT_MAX_REMAINING_LENGTH                   ( 268435455UL )
+
+/**
+ * @brief Set a bit in an 8-bit unsigned integer.
+ */
+#define UINT8_SET_BIT( x, position )      ( ( x ) = ( uint8_t ) ( ( x ) | ( 0x01U << ( position ) ) ) )
+
+/**
+ * @brief Macro for checking if a bit is set in a 1-byte unsigned int.
+ *
+ * @param[in] x The unsigned int to check.
+ * @param[in] position Which bit to check.
+ */
+#define UINT8_CHECK_BIT( x, position )    ( ( ( x ) & ( 0x01U << ( position ) ) ) == ( 0x01U << ( position ) ) )
+
+/**
+ * @brief Get the high byte of a 16-bit unsigned integer.
+ */
+#define UINT16_HIGH_BYTE( x )             ( ( uint8_t ) ( ( x ) >> 8 ) )
+
+/**
+ * @brief Get the low byte of a 16-bit unsigned integer.
+ */
+#define UINT16_LOW_BYTE( x )              ( ( uint8_t ) ( ( x ) & 0x00ffU ) )
+
+/**
+ * @brief Macro for decoding a 2-byte unsigned int from a sequence of bytes.
+ *
+ * @param[in] ptr A uint8_t* that points to the high byte.
+ */
+#define UINT16_DECODE( ptr )                                \
+    ( uint16_t ) ( ( ( ( uint16_t ) ( *( ptr ) ) ) << 8 ) | \
+                   ( ( uint16_t ) ( *( ( ptr ) + 1 ) ) ) )
+
+/**
+ * @brief A value that represents an invalid remaining length.
+ *
+ * This value is greater than what is allowed by the MQTT specification.
+ */
+#define MQTT_REMAINING_LENGTH_INVALID             ( ( size_t ) 268435456 )
+
+/**
+ * @brief The minimum remaining length for a QoS 0 PUBLISH.
+ *
+ * Includes two bytes for topic name length and one byte for topic name.
+ */
+#define MQTT_MIN_PUBLISH_REMAINING_LENGTH_QOS0    ( 3U )
+
+/*-----------------------------------------------------------*/
+
+
 /**
  * @brief MQTT Subscription packet types.
  */
diff --git a/source/include/core_mqtt_serializer.h b/source/include/core_mqtt_serializer.h
index 002b44d3e..de849eeea 100644
--- a/source/include/core_mqtt_serializer.h
+++ b/source/include/core_mqtt_serializer.h
@@ -76,116 +76,6 @@
 #define MQTT_PACKET_TYPE_DISCONNECT     ( ( uint8_t ) 0xE0U )  /**< @brief DISCONNECT (client-to-server). */
 /** @} */
 
-/**
- * @brief MQTT protocol version 3.1.1.
- */
-#define MQTT_VERSION_3_1_1                          ( ( uint8_t ) 4U )
-
-/**
- * @brief Size of the fixed and variable header of a CONNECT packet.
- */
-#define MQTT_PACKET_CONNECT_HEADER_SIZE             ( 10UL )
-
-/* MQTT CONNECT flags. */
-#define MQTT_CONNECT_FLAG_CLEAN                     ( 1 ) /**< @brief Clean session. */
-#define MQTT_CONNECT_FLAG_WILL                      ( 2 ) /**< @brief Will present. */
-#define MQTT_CONNECT_FLAG_WILL_QOS1                 ( 3 ) /**< @brief Will QoS 1. */
-#define MQTT_CONNECT_FLAG_WILL_QOS2                 ( 4 ) /**< @brief Will QoS 2. */
-#define MQTT_CONNECT_FLAG_WILL_RETAIN               ( 5 ) /**< @brief Will retain. */
-#define MQTT_CONNECT_FLAG_PASSWORD                  ( 6 ) /**< @brief Password present. */
-#define MQTT_CONNECT_FLAG_USERNAME                  ( 7 ) /**< @brief User name present. */
-
-/*
- * Positions of each flag in the first byte of an MQTT PUBLISH packet's
- * fixed header.
- */
-#define MQTT_PUBLISH_FLAG_RETAIN                    ( 0 ) /**< @brief MQTT PUBLISH retain flag. */
-#define MQTT_PUBLISH_FLAG_QOS1                      ( 1 ) /**< @brief MQTT PUBLISH QoS1 flag. */
-#define MQTT_PUBLISH_FLAG_QOS2                      ( 2 ) /**< @brief MQTT PUBLISH QoS2 flag. */
-#define MQTT_PUBLISH_FLAG_DUP                       ( 3 ) /**< @brief MQTT PUBLISH duplicate flag. */
-
-/**
- * @brief The size of MQTT DISCONNECT packets, per MQTT spec.
- */
-#define MQTT_DISCONNECT_PACKET_SIZE                 ( 2UL )
-
-/**
- * @brief A PINGREQ packet is always 2 bytes in size, defined by MQTT 3.1.1 spec.
- */
-#define MQTT_PACKET_PINGREQ_SIZE                    ( 2UL )
-
-/**
- * @brief The Remaining Length field of MQTT disconnect packets, per MQTT spec.
- */
-#define MQTT_DISCONNECT_REMAINING_LENGTH            ( ( uint8_t ) 0 )
-
-/*
- * Constants relating to CONNACK packets, defined by MQTT 3.1.1 spec.
- */
-#define MQTT_PACKET_CONNACK_REMAINING_LENGTH        ( ( uint8_t ) 2U )    /**< @brief A CONNACK packet always has a "Remaining length" of 2. */
-#define MQTT_PACKET_CONNACK_SESSION_PRESENT_MASK    ( ( uint8_t ) 0x01U ) /**< @brief The "Session Present" bit is always the lowest bit. */
-
-/*
- * UNSUBACK, PUBACK, PUBREC, PUBREL, and PUBCOMP always have a remaining length
- * of 2.
- */
-#define MQTT_PACKET_SIMPLE_ACK_REMAINING_LENGTH     ( ( uint8_t ) 2 ) /**< @brief PUBACK, PUBREC, PUBREl, PUBCOMP, UNSUBACK Remaining length. */
-#define MQTT_PACKET_PINGRESP_REMAINING_LENGTH       ( 0U )            /**< @brief A PINGRESP packet always has a "Remaining length" of 0. */
-
-/**
- * @brief Per the MQTT 3.1.1 spec, the largest "Remaining Length" of an MQTT
- * packet is this value, 256 MB.
- */
-#define MQTT_MAX_REMAINING_LENGTH                   ( 268435455UL )
-
-/**
- * @brief Set a bit in an 8-bit unsigned integer.
- */
-#define UINT8_SET_BIT( x, position )      ( ( x ) = ( uint8_t ) ( ( x ) | ( 0x01U << ( position ) ) ) )
-
-/**
- * @brief Macro for checking if a bit is set in a 1-byte unsigned int.
- *
- * @param[in] x The unsigned int to check.
- * @param[in] position Which bit to check.
- */
-#define UINT8_CHECK_BIT( x, position )    ( ( ( x ) & ( 0x01U << ( position ) ) ) == ( 0x01U << ( position ) ) )
-
-/**
- * @brief Get the high byte of a 16-bit unsigned integer.
- */
-#define UINT16_HIGH_BYTE( x )             ( ( uint8_t ) ( ( x ) >> 8 ) )
-
-/**
- * @brief Get the low byte of a 16-bit unsigned integer.
- */
-#define UINT16_LOW_BYTE( x )              ( ( uint8_t ) ( ( x ) & 0x00ffU ) )
-
-/**
- * @brief Macro for decoding a 2-byte unsigned int from a sequence of bytes.
- *
- * @param[in] ptr A uint8_t* that points to the high byte.
- */
-#define UINT16_DECODE( ptr )                                \
-    ( uint16_t ) ( ( ( ( uint16_t ) ( *( ptr ) ) ) << 8 ) | \
-                   ( ( uint16_t ) ( *( ( ptr ) + 1 ) ) ) )
-
-/**
- * @brief A value that represents an invalid remaining length.
- *
- * This value is greater than what is allowed by the MQTT specification.
- */
-#define MQTT_REMAINING_LENGTH_INVALID             ( ( size_t ) 268435456 )
-
-/**
- * @brief The minimum remaining length for a QoS 0 PUBLISH.
- *
- * Includes two bytes for topic name length and one byte for topic name.
- */
-#define MQTT_MIN_PUBLISH_REMAINING_LENGTH_QOS0    ( 3U )
-
-/*-----------------------------------------------------------*/
-
 /**
  * @ingroup mqtt_constants
  * @brief The size of MQTT PUBACK, PUBREC, PUBREL, and PUBCOMP packets, per MQTT spec.

From 8b678c59374d4a4b627c047afac8efe829dd92dd Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Mon, 29 Aug 2022 14:02:04 -0700
Subject: [PATCH 33/35] update comments to clarify write requirements

---
 source/interface/transport_interface.h | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index a884e7ee2..3ec1556da 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -261,7 +261,13 @@ typedef struct TransportOutVector
 
 /**
  * @transportcallback
- * @brief Transport interface function for "vectored" / scatter-gather based writes.
+ * @brief Transport interface function for "vectored" / scatter-gather based
+ * writes. This function is expected to iterate over the list of vectors pIoVec
+ * having ioVecCount entries containing portions of one MQTT message at a maximum.
+ * If the proper functionality is available, then the data in the list should be
+ * copied to the underlying TCP buffer before flushing the buffer. Implementing it
+ * in this fashion  will lead to sending of fewer TCP packets for all the values
+ * in the list.
  *
  * @param[in] pNetworkContext Implementation-defined network context.
  * @param[in] pIoVec An array of TransportIoVector_t structs.
@@ -271,7 +277,7 @@ typedef struct TransportOutVector
  *
  * @note If no data is written to the buffer due to the buffer being full this MUST
  * return zero as the return value.
- * A zero return value SHOULD represent that the send operation can be retried
+ * A zero return value SHOULD represent that the write operation can be retried
  * by calling the API function. Zero MUST NOT be returned if a network disconnection
  * has occurred.
  */

From 732172e18d89a743d89d98bc55626179ed8cb7e4 Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Mon, 29 Aug 2022 14:35:25 -0700
Subject: [PATCH 34/35] Add a note for write function pointer

---
 source/interface/transport_interface.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/source/interface/transport_interface.h b/source/interface/transport_interface.h
index 3ec1556da..d97495bde 100644
--- a/source/interface/transport_interface.h
+++ b/source/interface/transport_interface.h
@@ -269,6 +269,10 @@ typedef struct TransportOutVector
  * in this fashion  will lead to sending of fewer TCP packets for all the values
  * in the list.
  *
+ * @note If the proper write functionality is not present for a given device/IP-stack,
+ * then there is no strict requirement to implement write. Only the send and recv
+ * interfaces must be defined for the application to work properly.
+ *
  * @param[in] pNetworkContext Implementation-defined network context.
  * @param[in] pIoVec An array of TransportIoVector_t structs.
  * @param[in] ioVecCount Number of TransportIoVector_t in pIoVec.

From a041162a4ca06b4e9fd718e0e7fa8d59daf3a06d Mon Sep 17 00:00:00 2001
From: Aniruddha Kanhere <60444055+AniruddhaKanhere@users.noreply.github.com>
Date: Mon, 29 Aug 2022 14:46:03 -0700
Subject: [PATCH 35/35] Fix spell check

---
 lexicon.txt | 1 +
 1 file changed, 1 insertion(+)

diff --git a/lexicon.txt b/lexicon.txt
index 3877e2127..255889b2b 100644
--- a/lexicon.txt
+++ b/lexicon.txt
@@ -115,6 +115,7 @@ int
 io
 iot
 ioveccount
+ip
 isn
 iso
 keepaliveintervalsec