#include <windows.h>
#include <stdio.h>

#define LOG_BUFFER		512
#define LOG_PREFIX		"Application1"
#define PATH_APPLICATION	"C:\\Temp"

int Logging_LogSystem(char *szLogFormat, ...);

int main()
{
	Logging_LogSystem("This function can be called in a similar fashion to %s.\r\n", "printf()");
	Logging_LogSystem("It's handy for capturing application log or error data (which includes numbers like %d).\r\n", 5);
	Logging_LogSystem("Using a log buffer size of 0x%X bytes.\r\n", LOG_BUFFER);

	return 0;
}

int Logging_LogSystem(char *szLogFormat, ...)
{
	SYSTEMTIME sTime;	
	HANDLE hLogFile = NULL;
	DWORD dwLength = 0;	
	char szLogString[LOG_BUFFER], szFileName[MAX_PATH], szDateTime[LOG_BUFFER], szErrorString[LOG_BUFFER];
	char *szVarList;
	int iRetVal = TRUE;

	va_start(szVarList, szLogFormat);
	if (_vsnprintf_s(szLogString, sizeof(szLogString), _TRUNCATE, szLogFormat, szVarList) == -1)
		szLogString[sizeof(szLogString) - 1] = '\0';	
	va_end(szVarList);

	GetLocalTime(&sTime);

	sprintf_s(szFileName, sizeof(szFileName), "%s\\Logs\\%s-%04d%02d%02d.Log", PATH_APPLICATION, LOG_PREFIX, sTime.wYear, sTime.wMonth, sTime.wDay);
	
	hLogFile = CreateFile(szFileName, GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
	if (hLogFile != INVALID_HANDLE_VALUE)
	{
		if (SetFilePointer(hLogFile, 0, 0, FILE_END) == INVALID_SET_FILE_POINTER)
		{
			sprintf_s(szErrorString, sizeof(szErrorString), "Error: %s() - %s() - %d\r\n", __FUNCTION__, "SetFilePointer", GetLastError());
			iRetVal = FALSE;
			goto Error;
		}

		sprintf_s(szDateTime, sizeof(szDateTime), "%02d:%02d:%02d ", sTime.wHour, sTime.wMinute, sTime.wSecond);

		if (!WriteFile(hLogFile, szDateTime, (int) strlen(szDateTime), &dwLength, NULL))
		{
			sprintf_s(szErrorString, sizeof(szErrorString), "Error: %s() - %s() - %d\r\n", __FUNCTION__, "WriteFile", GetLastError());
			iRetVal = FALSE;
			goto Error;
		}

		if (!WriteFile(hLogFile, szLogString, (int) strlen(szLogString), &dwLength, NULL))
		{
			sprintf_s(szErrorString, sizeof(szErrorString), "Error: %s() - %s() - %d\r\n", __FUNCTION__, "WriteFile", GetLastError());
			iRetVal = FALSE;
			goto Error;
		}
	}
	else
	{
		sprintf_s(szErrorString, sizeof(szErrorString), "Error: %s() - %s() - %d\r\n", __FUNCTION__, "CreateFile", GetLastError());
		iRetVal = FALSE;
		goto Error;
	}

	goto Cleanup;

Error:
	// Use alternate log for error condition (Syslog, Event Log etc)
	// Error captured in szErrorString

	printf(szErrorString);

Cleanup:
	if (hLogFile)
		CloseHandle(hLogFile);

	return iRetVal;
}