CClientUDPSocket::SendTo() and CUDPSocket::SendTo() Optimize for eMule

eMule 49b. TK4 Mod 2.2b

A code optimize in the TK4 MOD from version 2.0c, (based on eMule 47c), this page contains information originally posted to the eMule forum at that time.

eMule Version: 0.47c, 0.48a
Files changed: ClientUDPSocket.cpp and UDPSocket.cpp

eMule Forum Discussion thread entry point account required,(free)
eMule Forum Discussion thread entry point account required,(free)

I was doing some profiling...

When I noted that in CClientUDPSocket::SendTo() ipstr() took, what I believed to be, an excessive execution time for what it did. So, I looked at the code,(see the current code below). ipstr() returns a CString object and for eMule that's a CStringT object. Now CString objects seem expensive to me anyway, but when I looked at int CAsyncSocket::SendTo(const void* lpBuf, int nBufLen, UINT nHostPort, LPCTSTR lpszHostAddress, int nFlags) I found the first thing it does to our newly created TChar CString is convert it to an ASCII string, it then takes that ASCII string and with inet_addr(lpszAscii); turns it back to the uint32 value we started with in dwIP!!
Finally it makes a call to SendTo(lpBuf, nBufLen, (SOCKADDR*)&sockAddr, sizeof(sockAddr), nFlags);

Note: The INADDR_NONE error returned by inet_addr() has the value 0xffffffff which equals 255.255.255.255, the limited broadcast address,(INADDR_BROADCAST). Therefore passing 255.255.255.255/INADDR_BROADCAST would result in an error being returned by int CAsyncSocket::SendTo(const void* lpBuf, int nBufLen, UINT nHostPort, LPCTSTR lpszHostAddress, int nFlags).

The code as is (47c/48a):

CODE: Original CClientUDPSocket::SendTo()

int CClientUDPSocket::SendTo(char* lpBuf,int nBufLen,uint32 dwIP, uint16 nPort){
	// NOTE: *** This function is invoked from a *different* thread!
	uint32 result = CAsyncSocket::SendTo(lpBuf,nBufLen,nPort,ipstr(dwIP));
	if (result == (uint32)SOCKET_ERROR){
		uint32 error = GetLastError();
		if (error == WSAEWOULDBLOCK){
			m_bWouldBlock = true;
			return -1;
		}
		if (thePrefs.GetVerbose())
			DebugLogError(_T("Error: Client UDP socket, failed to send data to %s:%u: %s"), ipstr(dwIP), nPort, GetErrorMessage(error, 1));
	}
	return 0;
}

Where the waste is...

CODE: MFC CAsyncSocket::CAsyncSocket::SendTo(const void* lpBuf, int nBufLen, UINT nHostPort, LPCTSTR lpszHostAddress, int nFlags)


// This is a part of the Microsoft Foundation Classes C++ library.
// Copyright © Microsoft Corporation
// All rights reserved.
//
// This source code is only intended as a supplement to the
// Microsoft Foundation Classes Reference and related
// electronic documentation provided with the library.
// See these sources for detailed information regarding the
// Microsoft Foundation Classes product.
int CAsyncSocket::SendTo(const void* lpBuf, int nBufLen, UINT nHostPort, LPCTSTR lpszHostAddress, int nFlags)
{
	USES_CONVERSION_EX;

	SOCKADDR_IN sockAddr;

	memset(&sockAddr,0,sizeof(sockAddr));

	LPSTR lpszAscii;
	if (lpszHostAddress != NULL)
	{
		lpszAscii = T2A_EX((LPTSTR)lpszHostAddress, _ATL_SAFE_ALLOCA_DEF_THRESHOLD);
		if (lpszAscii == NULL)
		{
			// OUT OF MEMORY
			WSASetLastError(ERROR_NOT_ENOUGH_MEMORY);
			return FALSE;
		}	
	}
	else
	{
		lpszAscii = NULL;
	}

	sockAddr.sin_family = AF_INET;

	if (lpszAscii == NULL)
		sockAddr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
	else
	{
		sockAddr.sin_addr.s_addr = inet_addr(lpszAscii);
		if (sockAddr.sin_addr.s_addr == INADDR_NONE)
		{
			LPHOSTENT lphost;
			lphost = gethostbyname(lpszAscii);
			if (lphost != NULL)
				sockAddr.sin_addr.s_addr = ((LPIN_ADDR)lphost->h_addr)->s_addr;
			else
			{
				WSASetLastError(WSAEINVAL);
				return SOCKET_ERROR;
			}
		}
	}

	sockAddr.sin_port = htons((u_short)nHostPort);

	return SendTo(lpBuf, nBufLen, (SOCKADDR*)&sockAddr, sizeof(sockAddr), nFlags);
}

What the waste is... Note: bold purple indicates the code retained to form the optimizated replacement for this function.

CODE: MFC CAsyncSocket::CAsyncSocket::SendTo(const void* lpBuf, int nBufLen, UINT nHostPort, LPCTSTR lpszHostAddress, int nFlags)Annotated version

// This is a part of the Microsoft Foundation Classes C++ library.
// Copyright © Microsoft Corporation
// All rights reserved.
//
// This source code is only intended as a supplement to the
// Microsoft Foundation Classes Reference and related
// electronic documentation provided with the library.
// See these sources for detailed information regarding the
// Microsoft Foundation Classes product.
int CAsyncSocket::SendTo(const void* lpBuf, int nBufLen, UINT nHostPort, LPCTSTR lpszHostAddress, int nFlags)
{
	USES_CONVERSION_EX;

	SOCKADDR_IN sockAddr; <- Retained

	memset(&sockAddr,0,sizeof(sockAddr)); <- Retained


	LPSTR lpszAscii;
	if (lpszHostAddress != NULL)
	{
		lpszAscii = T2A_EX((LPTSTR)lpszHostAddress, _ATL_SAFE_ALLOCA_DEF_THRESHOLD);
		if (lpszAscii == NULL)
		{
			// OUT OF MEMORY
			WSASetLastError(ERROR_NOT_ENOUGH_MEMORY);
			return FALSE;
		}	
	}
	else
	{
		lpszAscii = NULL;
	}


        ^^^^^ Above String conversion only       

	sockAddr.sin_family = AF_INET; <- Retained

	if (lpszAscii == NULL)     <- To deal with and empty string being passed, can never happen with the original code
		sockAddr.sin_addr.s_addr = htonl(INADDR_BROADCAST); <--- Why htonl?? #define INADDR_BROADCAST        (u_long)0xffffffff   
	else
	{
		sockAddr.sin_addr.s_addr = inet_addr(lpszAscii); <--- ***THIS LINE Returns the value dwIP !!!
		if (sockAddr.sin_addr.s_addr == INADDR_NONE) <--- Deals with an error returned by inet_addr() BUT also could occur if INADDR_BROADCAST address is passed!!
		{
			LPHOSTENT lphost;
			lphost = gethostbyname(lpszAscii); <-- A check to see if a host name had been passed in the original string, not applicable to our code
			if (lphost != NULL)
				sockAddr.sin_addr.s_addr = ((LPIN_ADDR)lphost->h_addr)->s_addr;
			else
			{                                   
				WSASetLastError(WSAEINVAL);                             <-- Just added to the optimize for 255.255.255.255
				return SOCKET_ERROR; 
			}
		}
	}

	sockAddr.sin_port = htons((u_short)nHostPort); <--- Retained

	return SendTo(lpBuf, nBufLen, (SOCKADDR*)&sockAddr, sizeof(sockAddr), nFlags); <--- Call Retained
}

Optimized code

CODE: My optimized version of CClientUDPSocket::SendTo()

int CClientUDPSocket::SendTo(char* lpBuf,int nBufLen,uint32 dwIP, uint16 nPort){
	 // NOTE: *** This function is invoked from a *different* thread!
	//TK4 MOD 2.0c - Save converting dwIP from uint32 to a CStringT to ASCII then back to uint32
	if(dwIP == INADDR_BROADCAST)
	  {
            WSASetLastError(WSAEINVAL);
	    if (thePrefs.GetVerbose())
			DebugLogError(_T("Error: Client UDP socket, failed to send data to %s:%u: %s"), ipstr(dwIP), nPort, GetErrorMessage(WSAEINVAL, 1));
            return 0;
	   }

	SOCKADDR_IN sockAddr;
	memset(&sockAddr, 0,sizeof(sockAddr));
 	sockAddr.sin_family = AF_INET;
	sockAddr.sin_addr.s_addr = dwIP;
	sockAddr.sin_port = htons((u_short)nPort);

	uint32 result = CAsyncSocket::SendTo(lpBuf, nBufLen, (SOCKADDR*)&sockAddr, sizeof(sockAddr), 0);

//	uint32 result = CAsyncSocket::SendTo(lpBuf,nBufLen,nPort,ipstr(dwIP)); 

	if (result == (uint32)SOCKET_ERROR){
		uint32 error = GetLastError();
		if (error == WSAEWOULDBLOCK){
			m_bWouldBlock = true;
			return -1;
		}
		if (thePrefs.GetVerbose())
			DebugLogError(_T("Error: Client UDP socket, failed to send data to %s:%u: %s"), ipstr(dwIP), nPort, GetErrorMessage(error, 1));
	}
	return 0;
}

Optimized code

CODE: The same optimize can be applied to CUDPSocket::SendTo()

int CUDPSocket::SendTo(BYTE* lpBuf, int nBufLen, uint32 dwIP, uint16 nPort)
{
	// NOTE: *** This function is invoked from a *different* thread!
	//TK4 MOD 2.0c - Save converting dwIP from uint32 to a CStringT to ASCII then back to uint32
	if(dwIP == INADDR_BROADCAST)
	  {
            WSASetLastError(WSAEINVAL);
	    if (thePrefs.GetVerbose())
			DebugLogError(_T("Error: Client UDP socket, failed to send data to %s:%u: %s"), ipstr(dwIP), nPort, GetErrorMessage(WSAEINVAL, 1));
            return 0;
	   }

	SOCKADDR_IN sockAddr;
	memset(&sockAddr, 0,sizeof(sockAddr));
	sockAddr.sin_family = AF_INET;
	sockAddr.sin_addr.s_addr = dwIP;
	sockAddr.sin_port = htons((u_short)nPort);

	int iResult = CAsyncSocket::SendTo(lpBuf, nBufLen, (SOCKADDR*)&sockAddr, sizeof(sockAddr), 0);

	//int iResult = CAsyncSocket::SendTo(lpBuf, nBufLen, nPort, ipstr(dwIP));
	if (iResult == SOCKET_ERROR) {
		DWORD dwError = GetLastError();
		if (dwError == WSAEWOULDBLOCK) {
			m_bWouldBlock = true;
			return -1; // blocked
		}
		else{
			if (thePrefs.GetVerbose())
				theApp.QueueDebugLogLine(false, _T("Error: Server UDP socket: Failed to send packet to %s:%u - %s"), ipstr(dwIP), nPort, GetErrorMessage(dwError, 1));
			return 0; // error
		}
	}
	return 1; // success
}