consolidate multiple buffers from async_write_some to single SendBuffer

libi2pd/Streaming.cpp

@@ -19,6 +19,26 @@ namespace i2p
 {
 namespace stream
 {
+	SendBuffer::SendBuffer (const std::vector<std::pair<const uint8_t *, size_t> >& bufs, size_t totalLen, SendHandler&& h):
+		len(totalLen), offset (0), handler(std::move (h))
+	{
+		buf = new uint8_t[len];
+		size_t offset1 = 0;
+		for (const auto& [b, l]: bufs)
+		{
+			if (offset1 + l <= totalLen)
+			{
+				memcpy (buf + offset1, b, l);
+				offset1 += l;
+			}
+			else
+			{
+				memcpy (buf + offset1, b, totalLen - offset1);
+				break;
+			}
+		}
+	}
+
 	void SendBufferQueue::Add (std::shared_ptr<SendBuffer>&& buf)
 	{
 		if (buf)
@@ -939,13 +959,22 @@ namespace stream
 		std::shared_ptr<i2p::stream::SendBuffer> buffer;
 		if (len > 0 && buf)
 			buffer = std::make_shared<i2p::stream::SendBuffer>(buf, len, std::move (handler));
-		else if (handler)
-			handler(boost::system::error_code ());
-		auto s = shared_from_this ();
-		boost::asio::post (m_Service, [s, buffer = std::move(buffer)]() mutable
+		else
+		{
+			if (handler)
+				handler(boost::system::error_code ());
+			return;
+		}
+		Send (std::move (buffer));
+	}
+
+	void Stream::Send (std::shared_ptr<i2p::stream::SendBuffer>&& buf)
+	{
+		if (!buf) return;
+		boost::asio::post (m_Service, [s = shared_from_this (), buf = std::move(buf)]() mutable
 			{
-				if (buffer)
-					s->m_SendBuffer.Add (std::move(buffer));
+				if (buf)
+					s->m_SendBuffer.Add (std::move(buf));
 				s->SendBuffer ();
 			});
 	}

libi2pd/Streaming.h

@@ -144,6 +144,7 @@ namespace stream
 		{
 			buf = new uint8_t[len];
 		}
+		SendBuffer (const std::vector<std::pair<const uint8_t *, size_t> >& bufs, size_t totalLen, SendHandler&& h);
 		~SendBuffer ()
 		{
 			delete[] buf;
@@ -209,6 +210,7 @@ namespace stream
 			void HandlePing (Packet * packet);
 			size_t Send (const uint8_t * buf, size_t len);
 			void AsyncSend (const uint8_t * buf, size_t len, SendHandler&& handler);
+			void Send (std::shared_ptr<i2p::stream::SendBuffer>&& buf);
 			void SendPing ();
 
 			template<typename Buffer, typename ReceiveHandler>

libi2pd_client/BoostStream.h

@@ -57,15 +57,36 @@ namespace client
 			template<typename ConstBufferSequence, typename WriteHandler>
 			void async_write_some(const ConstBufferSequence& bufs, WriteHandler&& handler)
 			{
+				std::vector<std::pair<const uint8_t *, size_t> > bufsToSend;
 				size_t sent = 0;
 				for (auto it = boost::asio::buffer_sequence_begin (bufs); it != boost::asio::buffer_sequence_end (bufs); it++)
 				{
 					const auto& buf = *it;
 					sent += buf.size ();
-					m_Stream->Send ((const uint8_t *)buf.data (), buf.size ());
-					// TODO: AsyncSend wiht callback for last buf, but not possible below C++23
+					bufsToSend.push_back ({ (const uint8_t *)buf.data (), buf.size () });
+
 				}
-				handler (boost::system::error_code (), sent);
+				if (sent)
+				{
+#ifdef __cpp_lib_move_only_function // with C++23
+					// we can save handler with SendBuffer
+					auto sendBuffer = std::make_shared<i2p::stream::SendBuffer>(bufsToSend, sent,
+						[handler = std::move (handler), sent](const boost::system::error_code& ecode) mutable
+						{
+							handler (ecode, sent);
+						});
+#else
+					// we can't save handler with SendBuffer due to lack of std::move_only_function
+					auto sendBuffer = std::make_shared<i2p::stream::SendBuffer>(bufsToSend, sent, nullptr);
+#endif
+					m_Stream->Send (std::move (sendBuffer));
+#ifndef __cpp_lib_move_only_function // no std::move_only_function
+					// invoke handler right after send
+					handler (boost::system::error_code (), sent);
+#endif
+				}
+				else
+					handler (boost::system::error_code (), 0);
 			}
 
 		private: