/*** *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