77 lines
1.7 KiB
C++
77 lines
1.7 KiB
C++
/***
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*xlock.cpp - thread lock class
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*
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* Copyright (c) 1996-2001, Microsoft Corporation. All rights reserved.
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*
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*Purpose:
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* Define lock class used to make STD C++ Library thread-safe.
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*
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*Revision History:
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* 08-28-96 GJF Module created, MGHMOM.
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*
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*******************************************************************************/
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#ifdef _MT
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#include <xstddef>
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#include <windows.h>
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_STD_BEGIN
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static CRITICAL_SECTION _CritSec;
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static long _InitFlag = 0L;
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static void _CleanUp()
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{
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long InitFlagValue;
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if ( InitFlagValue = InterlockedExchange( &_InitFlag, 3L ) == 2L )
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// Should be okay to delete critical section
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DeleteCriticalSection( &_CritSec );
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}
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_Lockit::_Lockit()
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{
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// Most common case - just enter the critical section
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if ( _InitFlag == 2L ) {
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EnterCriticalSection( &_CritSec );
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return;
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}
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// Critical section either needs to be initialized.
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if ( _InitFlag == 0L ) {
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long InitFlagVal;
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if ( (InitFlagVal = InterlockedExchange( &_InitFlag, 1L )) == 0L ) {
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InitializeCriticalSection( &_CritSec );
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atexit( _CleanUp );
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_InitFlag = 2L;
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}
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else if ( InitFlagVal == 2L )
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_InitFlag = 2L;
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}
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// If necessary, wait while another thread finishes initializing the
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// critical section
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while ( _InitFlag == 1L )
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Sleep( 1 );
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if ( _InitFlag == 2L )
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EnterCriticalSection( &_CritSec );
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}
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_Lockit::~_Lockit()
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{
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if ( _InitFlag == 2L )
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LeaveCriticalSection( &_CritSec );
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}
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_STD_END
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#endif
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