//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
//
// This source code is licensed under Microsoft Shared Source License
// Version 1.0 for Windows CE.
// For a copy of the license visit http://go.microsoft.com/fwlink/?LinkId=3223.
//
/***
*xlock.cpp - thread lock class
*
*Purpose:
* Define lock class used to make STD C++ Library thread-safe.
*
* This is only here to allow users to link with STL if _MT is defined
* when they build.
*
*******************************************************************************/
#ifndef _MT
#define _MT
#endif
#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
