Add an overload which accepts offset in ZmqSocket.Send(byte[] buffer, int offset, int size, int flags)

src/ZeroMQ/Interop/SocketProxy.cs

@@ -156,13 +156,13 @@ public byte[] Receive(byte[] buffer, int flags, out int size)
             return buffer;
         }
 
-        public int Send(byte[] buffer, int size, int flags)
+        public int Send(byte[] buffer, int offset, int size, int flags)
         {
             // Use zmq_buffer_send method if appropriate -> results in fewer P/Invoke calls
             if (buffer.Length <= MaxBufferSize && LibZmq.zmq_buffer_send != null)
             {
                 int sizeToSend = Math.Min(size, MaxBufferSize);
-                Marshal.Copy(buffer, 0, _buffer, sizeToSend);
+                Marshal.Copy(buffer, offset, _buffer, sizeToSend);
 
                 return Retry.IfInterrupted(LibZmq.zmq_buffer_send.Invoke, SocketHandle, _buffer, sizeToSend, flags);
             }
@@ -174,7 +174,7 @@ public int Send(byte[] buffer, int size, int flags)
 
             if (size > 0)
             {
-                Marshal.Copy(buffer, 0, _msg.Data(), size);
+                Marshal.Copy(buffer, offset, _msg.Data(), size);
             }
 
             int bytesSent = Retry.IfInterrupted(LibZmq.zmq_msg_send.Invoke, _msg.Ptr, SocketHandle, flags);

src/ZeroMQ/ZmqSocket.cs

@@ -713,6 +713,7 @@ public virtual byte[] Receive(byte[] buffer, SocketFlags flags, out int size)
         /// P/Invoke calls required to send the message buffer.
         /// </remarks>
         /// <param name="buffer">A <see cref="byte"/> array that contains the message to be sent.</param>
+        /// <param name="offset">The offset in buffer</param>
         /// <param name="size">The size of the message to send.</param>
         /// <param name="flags">A combination of <see cref="SocketFlags"/> values to use when sending.</param>
         /// <returns>The number of bytes sent by the socket.</returns>
@@ -721,7 +722,7 @@ public virtual byte[] Receive(byte[] buffer, SocketFlags flags, out int size)
         /// <exception cref="ZmqSocketException">An error occurred sending data to a remote endpoint.</exception>
         /// <exception cref="ObjectDisposedException">The <see cref="ZmqSocket"/> has been closed.</exception>
         /// <exception cref="NotSupportedException">The current socket type does not support Send operations.</exception>
-        public virtual int Send(byte[] buffer, int size, SocketFlags flags)
+        public virtual int Send(byte[] buffer, int offset, int size, SocketFlags flags)
         {
             EnsureNotDisposed();
 
@@ -735,7 +736,7 @@ public virtual int Send(byte[] buffer, int size, SocketFlags flags)
                 throw new ArgumentOutOfRangeException("size", "Expected a non-negative value less than or equal to the buffer length.");
             }
 
-            int sentBytes = _socketProxy.Send(buffer, size, (int)flags);
+            int sentBytes = _socketProxy.Send(buffer, offset, size, (int)flags);
 
             if (sentBytes >= 0)
             {
@@ -758,6 +759,28 @@ public virtual int Send(byte[] buffer, int size, SocketFlags flags)
             throw new ZmqSocketException(ErrorProxy.GetLastError());
         }
 
+        /// <summary>
+        /// Queue a message buffer to be sent by the socket in blocking mode.
+        /// </summary>
+        /// <remarks>
+        /// Performance tip: To increase send performance, especially on low-powered devices, restrict the
+        /// size of <paramref name="buffer"/> to <see cref="MaxBufferSize"/>. This will reduce the number of
+        /// P/Invoke calls required to send the message buffer.
+        /// </remarks>
+        /// <param name="buffer">A <see cref="byte"/> array that contains the message to be sent.</param>
+        /// <param name="size">The size of the message to send.</param>
+        /// <param name="flags">A combination of <see cref="SocketFlags"/> values to use when sending.</param>
+        /// <returns>The number of bytes sent by the socket.</returns>
+        /// <exception cref="ArgumentNullException"><paramref name="buffer"/> is null.</exception>
+        /// <exception cref="ArgumentOutOfRangeException"><paramref name="size"/> is a negative value or is larger than the length of <paramref name="buffer"/>.</exception>
+        /// <exception cref="ZmqSocketException">An error occurred sending data to a remote endpoint.</exception>
+        /// <exception cref="ObjectDisposedException">The <see cref="ZmqSocket"/> has been closed.</exception>
+        /// <exception cref="NotSupportedException">The current socket type does not support Send operations.</exception>
+        public virtual int Send(byte[] buffer, int size, SocketFlags flags)
+        {
+            return Send(buffer, 0, size, flags);
+        }
+
         /// <summary>
         /// Queue a message buffer to be sent by the socket in non-blocking mode with a specified timeout.
         /// </summary>