78 lines
1.7 KiB
C++
78 lines
1.7 KiB
C++
/***
|
|
*xlock.cpp - thread lock class
|
|
*
|
|
* Copyright (c) 1996-2001, 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
|