From 57b17d7cbb9b7c2b7f47cf9380f594df1f8b0e85 Mon Sep 17 00:00:00 2001
From: Badrish Chandramouli <badrishc@microsoft.com>
Date: Fri, 9 Jul 2021 07:54:19 -0700
Subject: [PATCH] [C#] Support FasterLog commit dir specification in settings
 (#519)

* Support log commit path specification to FasterLog.

* updates

* Convert serialized SpanByte into its non-serialized form (safe to heap-copy as long as underlying payload is fixed)
---
 cs/src/core/Device/LocalMemoryDevice.cs          |  5 +++--
 cs/src/core/Index/FasterLog/FasterLog.cs         |  1 +
 cs/src/core/Index/FasterLog/FasterLogSettings.cs |  7 ++++---
 cs/src/core/VarLen/SpanByte.cs                   | 11 +++++++++++
 cs/src/core/VarLen/SpanByteAndMemory.cs          |  1 +
 5 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/cs/src/core/Device/LocalMemoryDevice.cs b/cs/src/core/Device/LocalMemoryDevice.cs
index 17473d0a8..66c2ca0ef 100644
--- a/cs/src/core/Device/LocalMemoryDevice.cs
+++ b/cs/src/core/Device/LocalMemoryDevice.cs
@@ -43,8 +43,9 @@ public unsafe sealed class LocalMemoryDevice : StorageDeviceBase
         /// <param name="parallelism">Number of IO processing threads</param>
         /// <param name="latencyMs">Induced callback latency in ms (for testing purposes)</param>
         /// <param name="sector_size">Sector size for device (default 64)</param>
-        public LocalMemoryDevice(long capacity, long sz_segment, int parallelism, int latencyMs = 0, uint sector_size = 64)
-            : base("/userspace/ram/storage", sector_size, capacity)
+        /// <param name="fileName">Virtual path for the device</param>
+        public LocalMemoryDevice(long capacity, long sz_segment, int parallelism, int latencyMs = 0, uint sector_size = 64, string fileName = "/userspace/ram/storage")
+            : base(fileName, sector_size, capacity)
         {
             if (capacity == Devices.CAPACITY_UNSPECIFIED) throw new Exception("Local memory device must have a capacity!");
             Console.WriteLine("LocalMemoryDevice: Creating a " + capacity + " sized local memory device.");
diff --git a/cs/src/core/Index/FasterLog/FasterLog.cs b/cs/src/core/Index/FasterLog/FasterLog.cs
index c7980b70b..78dbb2a6c 100644
--- a/cs/src/core/Index/FasterLog/FasterLog.cs
+++ b/cs/src/core/Index/FasterLog/FasterLog.cs
@@ -139,6 +139,7 @@ private FasterLog(FasterLogSettings logSettings, bool oldCommitManager)
                 new DeviceLogCommitCheckpointManager
                 (new LocalStorageNamedDeviceFactory(),
                     new DefaultCheckpointNamingScheme(
+                        logSettings.LogCommitDir ??
                         new FileInfo(logSettings.LogDevice.FileName).Directory.FullName));
 
             if (logSettings.LogCommitManager == null)
diff --git a/cs/src/core/Index/FasterLog/FasterLogSettings.cs b/cs/src/core/Index/FasterLog/FasterLogSettings.cs
index ecb035f74..9fe7cc8e5 100644
--- a/cs/src/core/Index/FasterLog/FasterLogSettings.cs
+++ b/cs/src/core/Index/FasterLog/FasterLogSettings.cs
@@ -63,10 +63,11 @@ public class FasterLogSettings
         public ILogCommitManager LogCommitManager = null;
 
         /// <summary>
-        /// Use specified directory for storing and retrieving checkpoints
+        /// Use specified directory (path) as base for storing and retrieving log commits. By default,
+        /// commits will be stored in a folder named log-commits under this directory. If not provided, 
+        /// we use the base path of the log device by default.
         /// </summary>
-        [Obsolete("This field is obsolete. The default log commit manager uses its own naming system. To use the old commit manager, set FasterLogSettings.LogCommitManager = new LocalLogCommitManager(LogCommitFile).", false)]
-        public string LogCommitFile = null;
+        public string LogCommitDir = null;
 
         /// <summary>
         /// User callback to allocate memory for read entries
diff --git a/cs/src/core/VarLen/SpanByte.cs b/cs/src/core/VarLen/SpanByte.cs
index 78114e651..30f709379 100644
--- a/cs/src/core/VarLen/SpanByte.cs
+++ b/cs/src/core/VarLen/SpanByte.cs
@@ -107,6 +107,17 @@ public ReadOnlySpan<byte> AsReadOnlySpan()
                 return new ReadOnlySpan<byte>((void*)payload, Length);
         }
 
+        /// <summary>
+        /// If SpanByte is in a serialized form, return a non-serialized SpanByte wrapper that points to the same payload.
+        /// The resulting SpanByte is safe to heap-copy, as long as the underlying payload remains fixed.
+        /// </summary>
+        /// <returns></returns>
+        public SpanByte Deserialize()
+        {
+            if (!Serialized) return this;
+            return new SpanByte(Length, (IntPtr)Unsafe.AsPointer(ref payload));
+        }
+
         /// <summary>
         /// Reinterpret a fixed Span&lt;byte&gt; as a serialized SpanByte. Automatically adds Span length to the first 4 bytes.
         /// </summary>
diff --git a/cs/src/core/VarLen/SpanByteAndMemory.cs b/cs/src/core/VarLen/SpanByteAndMemory.cs
index da957ce97..1afb6de8b 100644
--- a/cs/src/core/VarLen/SpanByteAndMemory.cs
+++ b/cs/src/core/VarLen/SpanByteAndMemory.cs
@@ -28,6 +28,7 @@ public unsafe struct SpanByteAndMemory : IHeapConvertible
         /// <param name="spanByte"></param>
         public SpanByteAndMemory(SpanByte spanByte)
         {
+            if (spanByte.Serialized) throw new Exception("Cannot create new SpanByteAndMemory using serialized SpanByte");
             SpanByte = spanByte;
             Memory = default;
         }