Fixed TCP packet data corruption in non-blocking mode (#402, #119)

src/SFML/Network/TcpSocket.cpp

@@ -282,27 +282,28 @@ Socket::Status TcpSocket::send(Packet& packet)
     // This means that we have to send the packet size first, so that the
     // receiver knows the actual end of the packet in the data stream.
 
+    // We allocate an extra memory block so that the size can be sent
+    // together with the data in a single call. This may seem inefficient,
+    // but it is actually required to avoid partial send, which could cause
+    // data corruption on the receiving end.
+
     // Get the data to send from the packet
     std::size_t size = 0;
     const void* data = packet.onSend(size);
 
-    // First send the packet size
+    // First convert the packet size to network byte order
     Uint32 packetSize = htonl(static_cast<Uint32>(size));
-    Status status = send(reinterpret_cast<const char*>(&packetSize), sizeof(packetSize));
  
-    // Make sure that the size was properly sent
+    // Allocate memory for the data block to send
-    if (status != Done)
+    std::vector<char> blockToSend(sizeof(packetSize) + size);
-        return status;
  
-    // Send the packet data
+    // Copy the packet size and data into the block to send
-    if (packetSize > 0)
+    std::memcpy(&blockToSend[0], &packetSize, sizeof(packetSize));
-    {
+    if (size > 0)
-        return send(data, size);
+        std::memcpy(&blockToSend[0] + sizeof(packetSize), data, size);
-    }
+
-    else
+    // Send the data block
-    {
+    return send(&blockToSend[0], blockToSend.size());
-        return Done;
-    }
 }