manual merge of IPAddress from Arduino.cc arduino/Arduino@e3909b4

cores/esp8266/IPAddress.cpp

@@ -40,6 +40,47 @@ IPAddress::IPAddress(const uint8_t *address) {
     memcpy(_address.bytes, address, sizeof(_address.bytes));
 }
 
+bool IPAddress::fromString(const char *address) {
+    // TODO: add support for "a", "a.b", "a.b.c" formats
+
+    uint16_t acc = 0; // Accumulator
+    uint8_t dots = 0;
+
+    while (*address)
+    {
+        char c = *address++;
+        if (c >= '0' && c <= '9')
+        {
+            acc = acc * 10 + (c - '0');
+            if (acc > 255) {
+                // Value out of [0..255] range
+                return false;
+            }
+        }
+        else if (c == '.')
+        {
+            if (dots == 3) {
+                // Too much dots (there must be 3 dots)
+                return false;
+            }
+            _address.bytes[dots++] = acc;
+            acc = 0;
+        }
+        else
+        {
+            // Invalid char
+            return false;
+        }
+    }
+
+    if (dots != 3) {
+        // Too few dots (there must be 3 dots)
+        return false;
+    }
+    _address.bytes[3] = acc;
+    return true;
+}
+
 IPAddress& IPAddress::operator=(const uint8_t *address) {
     memcpy(_address.bytes, address, sizeof(_address.bytes));
     return *this;

cores/esp8266/IPAddress.h

@@ -48,6 +48,9 @@ class IPAddress: public Printable {
         IPAddress(uint32_t address);
         IPAddress(const uint8_t *address);
 
+        bool fromString(const char *address);
+        bool fromString(const String &address) { return fromString(address.c_str()); }
+
         // Overloaded cast operator to allow IPAddress objects to be used where a pointer
         // to a four-byte uint8_t array is expected
         operator uint32_t() const {