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150 lines
2.9 KiB
150 lines
2.9 KiB
/*++
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Copyright (c) 1995 Microsoft Corporation
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Module Name:
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Locks.hxx
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Abstract:
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Several small class (CInterlockedInteger, CMutexLock and CSharedLock
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which are wrappers for Win32 APIs.
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CInterlockedInteger is a simple wrapper for win32 interlockedm integer APis.
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CMutexLock is a wrapper designed to automatically constructed around
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win32 critical sections. They never forget to release the lock.
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CSharedLocks are similar to NT resources, they allow shared (multiple readers)
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and exclusive (single writer) access to the resource. They are different
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in the following ways:
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CSharedLocks don't starve exclusive threads.
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Exclusive threads spin (Sleep(0)) while waiting for readers to finish.
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Exclusive threads will deadlock trying to gain shared access.
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Exclusive threads trying to recursively take the lock may deadlock.
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They always block if they can't get access.
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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.?xx
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--*/
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#ifndef __LOCKS_HXX
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#define __LOCKS_HXX
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class CInterlockedInteger
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{
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private:
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LONG i;
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public:
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CInterlockedInteger(LONG i = 0) : i(i) {}
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LONG operator++(int)
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{
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return(InterlockedIncrement(&i));
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}
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LONG operator--(int)
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{
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return(InterlockedDecrement(&i));
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}
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operator LONG()
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{
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return(i);
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}
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};
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class CMutexLock
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{
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private:
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CRITICAL_SECTION *pCurrentLock;
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int owned;
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public:
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CMutexLock(CRITICAL_SECTION *pLock) : owned(0), pCurrentLock(pLock) {
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Lock();
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}
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~CMutexLock() {
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if (owned)
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Unlock();
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#if DBG
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pCurrentLock = 0;
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#endif
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}
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void Lock()
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{
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ASSERT(!owned);
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EnterCriticalSection(pCurrentLock);
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owned = 1;
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}
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void Unlock()
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{
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ASSERT(owned);
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owned = 0;
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LeaveCriticalSection(pCurrentLock);
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}
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};
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class CSharedLock
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{
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private:
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CRITICAL_SECTION lock;
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BOOL csinitokay;
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HANDLE hevent;
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CInterlockedInteger readers;
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CInterlockedInteger writers;
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DWORD exclusive_owner;
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public:
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CSharedLock(ORSTATUS &status);
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~CSharedLock();
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void LockShared(void);
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void UnlockShared(void);
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void LockExclusive(void);
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void UnlockExclusive(void);
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void Unlock(void);
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void ConvertToExclusive(void);
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BOOL HeldExclusive()
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{
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return(exclusive_owner == GetCurrentThreadId());
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}
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BOOL NotHeldExclusiveByAnyone()
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{
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return(exclusive_owner == 0);
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}
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private:
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void
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AssertValid()
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{
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ASSERT(csinitokay && hevent);
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}
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};
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#endif // __LOCKS_HXX
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