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Tricks of the Windows Gam…ming Gurus (2nd Edition)
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Disc2.iso
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vc98
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crt
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src
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xlock.cpp
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C/C++ Source or Header
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1998-06-16
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2KB
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77 lines
/***
*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 <xstddef>
#include <windows.h>
_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