C标准库源代码,能提高对C的理解,不错的哦

				/***
				*xlock.cpp - thread lock class
				*
				*       Copyright (c) 1996, Microsoft Corporation. All rights reserved.
				*
				*Purpose:
				*       Define lock class used to make STD C++ Library thread-safe.
				*
				*Revision History:
				*       08-28-96  GJF   Module created, MGHMOM.
				*
				*******************************************************************************/
				
				#ifdef  _MT
				
				#include 
				#include 
				_STD_BEGIN
				
				static CRITICAL_SECTION _CritSec;
				
				static long _InitFlag = 0L;
				
				static void _CleanUp()
				{
				        long InitFlagValue;
				
				        if ( InitFlagValue = InterlockedExchange( &_InitFlag, 3L ) == 2L )
				            // Should be okay to delete critical section
				            DeleteCriticalSection( &_CritSec );
				}
				
				_Lockit::_Lockit()
				{
				
				        // Most common case - just enter the critical section
				
				        if ( _InitFlag == 2L ) {
				            EnterCriticalSection( &_CritSec );
				            return;
				        }
				
				        // Critical section either needs to be initialized.
				
				        if ( _InitFlag == 0L ) {
				
				            long InitFlagVal;
				
				            if ( (InitFlagVal = InterlockedExchange( &_InitFlag, 1L )) == 0L ) {
				                InitializeCriticalSection( &_CritSec );
				                atexit( _CleanUp );
				                _InitFlag = 2L;
				            }
				            else if ( InitFlagVal == 2L )
				                _InitFlag = 2L;
				        }
				
				        // If necessary, wait while another thread finishes initializing the
				        // critical section
				
				        while ( _InitFlag == 1L )
				            Sleep( 1 );
				
				        if ( _InitFlag == 2L )
				            EnterCriticalSection( &_CritSec );
				}
				
				_Lockit::~_Lockit()
				{
				        if ( _InitFlag == 2L ) 
				            LeaveCriticalSection( &_CritSec );
				}
				
				_STD_END
				
				#endif