169 lines
3 KiB
C++
169 lines
3 KiB
C++
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/*++
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Copyright (C) Microsoft Corporation, 1995 - 1999
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Module Name:
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Locks.cxx
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Abstract:
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Out of line methods for some of the syncronization classes
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defined in locks.hxx.
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Author:
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Mario Goertzel [MarioGo]
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Revision History:
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MarioGo 03-14-95 Moved from misc.cxx.
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MarioGo 01-27-96 Changed from busy (Sleep(0)) wait to event
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--*/
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#include "qmgrlibp.h"
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#include <locks.hxx>
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BOOL BITSInitializeCriticalSectionInternal( LPCRITICAL_SECTION lpCriticalSection )
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{
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__try
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{
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InitializeCriticalSection( lpCriticalSection ); // SEC: REVIEWED 2002-03-28
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}
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__except( ( GetExceptionCode() == STATUS_NO_MEMORY ) ?
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EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH )
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{
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return FALSE;
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}
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return TRUE;
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}
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void BITSIntializeCriticalSection( LPCRITICAL_SECTION lpCriticalSection )
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{
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if (!BITSInitializeCriticalSectionInternal( lpCriticalSection ) )
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throw ComError( E_OUTOFMEMORY );
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}
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//
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// CShareLock methods
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//
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CSharedLock::CSharedLock()
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{
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exclusive_owner = 0;
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writers = 0;
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hevent = INVALID_HANDLE_VALUE; // Flag in the d'tor
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BITSIntializeCriticalSection( &lock );
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hevent = CreateEvent(0, FALSE, FALSE, 0); // SEC: REVIEWED 2002-03-28
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if (0 == hevent)
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{
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DeleteCriticalSection(&lock);
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throw ComError( E_OUTOFMEMORY );
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}
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}
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CSharedLock::~CSharedLock()
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{
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if (hevent != INVALID_HANDLE_VALUE)
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{
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DeleteCriticalSection(&lock);
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if (hevent) CloseHandle(hevent);
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}
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}
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void
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CSharedLock::LockShared()
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{
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readers++;
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if (writers)
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{
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if ((readers--) == 0)
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{
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SetEvent(hevent);
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}
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EnterCriticalSection(&lock);
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readers++;
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LeaveCriticalSection(&lock);
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}
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exclusive_owner = 0;
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}
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void
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CSharedLock::UnlockShared(void)
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{
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ASSERT((LONG)readers > 0);
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ASSERT(exclusive_owner == 0);
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if ( (readers--) == 0 && writers)
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{
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SetEvent(hevent);
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}
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}
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void
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CSharedLock::LockExclusive(void)
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{
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EnterCriticalSection(&lock);
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writers++;
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while(readers)
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{
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WaitForSingleObject(hevent, INFINITE);
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}
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ASSERT(writers);
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exclusive_owner = GetCurrentThreadId();
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}
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void
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CSharedLock::UnlockExclusive(void)
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{
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ASSERT(HeldExclusive());
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ASSERT(writers);
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writers--;
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exclusive_owner = 0;
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LeaveCriticalSection(&lock);
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}
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void
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CSharedLock::Unlock()
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{
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// Either the lock is held exclusively by this thread or the thread
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// has a shared lock. (or the caller has a bug).
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if (HeldExclusive())
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{
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UnlockExclusive();
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}
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else
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{
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UnlockShared();
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}
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}
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void
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CSharedLock::ConvertToExclusive(void)
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{
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ASSERT((LONG)readers > 0);
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ASSERT(exclusive_owner == 0);
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if ( (readers--) == 0 && writers )
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SetEvent(hevent);
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EnterCriticalSection(&lock);
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writers++;
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while(readers)
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{
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WaitForSingleObject(hevent, INFINITE);
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}
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ASSERT(writers);
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exclusive_owner = GetCurrentThreadId();
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}
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