From 7ab21c6afdaf4011b990a3a30c326b788d7d530d Mon Sep 17 00:00:00 2001
From: SChernykh <sergey.v.chernykh@gmail.com>
Date: Wed, 23 Feb 2022 17:07:50 +0100
Subject: [PATCH] TCPServer: reduced memory usage

---
 src/common.h       |  2 ++
 src/p2p_server.cpp |  2 +-
 src/tcp_server.h   |  2 +-
 src/tcp_server.inl | 12 ++++++++----
 4 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/src/common.h b/src/common.h
index d35ede1..2f37724 100644
--- a/src/common.h
+++ b/src/common.h
@@ -113,6 +113,8 @@ FORCEINLINE uint64_t udiv128(uint64_t hi, uint64_t lo, uint64_t divisor, uint64_
 }
 #endif
 
+template<typename T> FORCEINLINE T round_up(T a, size_t granularity) { return static_cast<T>(((a + (granularity - static_cast<size_t>(1))) / granularity) * granularity); }
+
 struct hash
 {
 	alignas(8) uint8_t h[HASH_SIZE];
diff --git a/src/p2p_server.cpp b/src/p2p_server.cpp
index 40d3287..8cecb0b 100644
--- a/src/p2p_server.cpp
+++ b/src/p2p_server.cpp
@@ -801,7 +801,7 @@ void P2PServer::on_broadcast()
 				}
 
 				return p - p0;
-				});
+			});
 		}
 	}
 }
diff --git a/src/tcp_server.h b/src/tcp_server.h
index e14c899..7b9db55 100644
--- a/src/tcp_server.h
+++ b/src/tcp_server.h
@@ -98,7 +98,7 @@ public:
 	{
 		Client* m_client;
 		uv_write_t m_write;
-		char m_data[WRITE_BUF_SIZE];
+		std::vector<uint8_t> m_data;
 	};
 
 	uv_mutex_t m_writeBuffersLock;
diff --git a/src/tcp_server.inl b/src/tcp_server.inl
index 4381f1f..6c40335 100644
--- a/src/tcp_server.inl
+++ b/src/tcp_server.inl
@@ -548,10 +548,12 @@ bool TCPServer<READ_BUF_SIZE, WRITE_BUF_SIZE>::send_internal(Client* client, Sen
 		buf = new WriteBuf();
 	}
 
-	const size_t bytes_written = callback(buf->m_data);
+	// callback_buf is used in only 1 thread, so it's safe
+	static uint8_t callback_buf[WRITE_BUF_SIZE];
+	const size_t bytes_written = callback(callback_buf);
 
-	if (bytes_written > sizeof(buf->m_data)) {
-		LOGERR(0, "send callback wrote " << bytes_written << " bytes, expected no more than " << sizeof(buf->m_data) << " bytes");
+	if (bytes_written > WRITE_BUF_SIZE) {
+		LOGERR(0, "send callback wrote " << bytes_written << " bytes, expected no more than " << WRITE_BUF_SIZE << " bytes");
 		panic();
 	}
 
@@ -566,9 +568,11 @@ bool TCPServer<READ_BUF_SIZE, WRITE_BUF_SIZE>::send_internal(Client* client, Sen
 
 	buf->m_client = client;
 	buf->m_write.data = buf;
+	buf->m_data.reserve(round_up(bytes_written, 64));
+	buf->m_data.assign(callback_buf, callback_buf + bytes_written);
 
 	uv_buf_t bufs[1];
-	bufs[0].base = buf->m_data;
+	bufs[0].base = reinterpret_cast<char*>(buf->m_data.data());
 	bufs[0].len = static_cast<int>(bytes_written);
 
 	const int err = uv_write(&buf->m_write, reinterpret_cast<uv_stream_t*>(&client->m_socket), bufs, 1, Client::on_write);