Fix SendPaquet thread safe issue

Creating a new write method that handle more than one buffer at once.

Thank to @ryancheung for pointing and for his PR cmangos/mangos-classic#311
Thank to @namreeb for his analyse.

close cmangos/mangos-classic#311

src/game/Server/WorldSocket.cpp

@@ -97,10 +97,10 @@ void WorldSocket::SendPacket(const WorldPacket& pct, bool immediate)
     ServerPktHeader header(pct.size() + 2, pct.GetOpcode());
     m_crypt.EncryptSend((uint8*)header.header, header.getHeaderLength());
 
-    Write((const char *)header.header, header.getHeaderLength());
-
-    if (!!pct.size())
-        Write((const char *)pct.contents(), pct.size());
+    if (pct.size() > 0)
+        Write(reinterpret_cast<const char *>(&header.header), header.getHeaderLength(), reinterpret_cast<const char *>(pct.contents()), pct.size());
+    else
+        Write(reinterpret_cast<const char *>(&header.header), header.getHeaderLength());
 
     if (immediate)
         ForceFlushOut();

src/shared/Network/Socket.cpp

@@ -162,28 +162,37 @@ bool Socket::Read(char *buffer, int length)
     return true;
 }
 
-void Socket::Write(const char *buffer, int length)
+void Socket::Write(const char *header, int headerSize, const char* content, int contentSize)
 {
     std::lock_guard<std::mutex> guard(m_mutex);
 
-    switch (m_writeState)
-    {
-        case WriteState::Idle:
-            m_outBuffer->Write(buffer, length);
-            StartWriteFlushTimer();
-            break;
+    // get the correct buffer depending on the current writing state
+    PacketBuffer* outBuffer = m_writeState == WriteState::Sending ? m_secondaryOutBuffer.get() : m_outBuffer.get();
 
-        case WriteState::Buffering:
-            m_outBuffer->Write(buffer, length);
-            break;
+    // write the header
+    outBuffer->Write(header, headerSize);
 
-        case WriteState::Sending:
-            m_secondaryOutBuffer->Write(buffer, length);
-            break;
+    // write the content
+    outBuffer->Write(content, contentSize);
 
-        default:
-            assert(false);
-    }
+    // flush data if need
+    if (m_writeState == WriteState::Idle)
+        StartWriteFlushTimer();
+}
+
+void Socket::Write(const char *buffer, int length)
+{
+    std::lock_guard<std::mutex> guard(m_mutex);
+
+    // get the correct buffer depending on the current writing state
+    PacketBuffer* outBuffer = m_writeState == WriteState::Sending ? m_secondaryOutBuffer.get() : m_outBuffer.get();
+
+    // write the header
+    outBuffer->Write(buffer, length);
+
+    // flush data if need
+    if (m_writeState == WriteState::Idle)
+        StartWriteFlushTimer();
 }
 
 // note that this function assumes that the socket mutex is locked

src/shared/Network/Socket.hpp

@@ -101,6 +101,7 @@ namespace MaNGOS
             void ReadSkip(int length) { m_inBuffer->Read(nullptr, length); }
 
             void Write(const char *buffer, int length);
+            void Write(const char *header, int headerSize, const char* content, int contentSize);
 
             boost::asio::ip::tcp::socket &GetAsioSocket() { return m_socket; }