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/*
* Copyright (c) 2005, Eric Crahen
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is furnished
* to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
* WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
*/
#ifndef __ZTFASTLOCK_H__
#define __ZTFASTLOCK_H__
#include "zthread/NonCopyable.h"
#include <windows.h>
#include <assert.h>
namespace ZThread {
/**
* @class FastLock
*
* @author Eric Crahen <http://www.code-foo.com>
* @date <2003-07-16T23:32:20-0400>
* @version 2.1.6
*
* This is the smallest and fastest synchronization object in the library.
* It is an implementation of fast mutex, an all or nothing exclusive
* lock. It should be used only where you need speed and are willing
* to sacrifice all the state & safety checking provided by the framework
* for speed.
*
* The current Platform SDK defines:
*
* LONG InterlockedExchange(LPLONG, LONG)
* LONG InterlockedCompareExchange(LPLONG, LONG, LONG, LONG)
*
* If your compiler complains about LPLONG not being implicitly casted to
* a PVOID, then you should get the SDK update from microsoft or use the
* WIN9X implementation of this class.
*
* ----
* Because Windows 95 and earlier can run on processors prior to the 486, they
* don't all support the CMPXCHG function, and so Windows 95 an earlier dont support
* InterlockedCompareExchange. For this, you should use the win9x implementation
* of this class
*/
class FastLock : private NonCopyable {
#pragma pack(push, 8)
LONG volatile _lock;
#pragma pack(pop)
public:
/**
* Create a new FastLock
*/
inline FastLock() : _lock(0) { }
/**
* Destroy FastLock
*/
inline ~FastLock() { assert(_lock == 0); }
/**
* Lock the fast Lock, no error check.
*
* @exception None
*/
inline void acquire() {
while (::InterlockedCompareExchange(const_cast<LPLONG>(&_lock), 1, 0) != 0)
::Sleep(0);
}
/**
* Release the fast Lock, no error check.
*
* @exception None
*/
inline void release() {
::InterlockedExchange(const_cast<LPLONG>(&_lock), (LONG)0);
}
/**
* Try to acquire an exclusive lock. No safety or state checks are performed.
* This function returns immediately regardless of the value of the timeout
*
* @param timeout Unused
* @return bool
* @exception Synchronization_Exception - not thrown
*/
inline bool tryAcquire(unsigned long timeout=0) {
return ::InterlockedCompareExchange(const_cast<LPLONG>(&_lock), 1, 0) == 0;
}
}; /* FastLock */
};
#endif
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