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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 __ZTFASTRECURSIVELOCK_H__
#define __ZTFASTRECURSIVELOCK_H__
#include "zthread/NonCopyable.h"
#include <windows.h>
#include <assert.h>
namespace ZThread {
/**
* @class FastRecursiveLock
*
* @author Eric Crahen <http://www.code-foo.com>
* @date <2003-07-16T23:32:34-0400>
* @version 2.1.6
*
* This is the smaller and faster implementation of a RecursiveLock.
* A single thread can acquire the mutex any number of times, but it
* must perform a release for each acquire(). Other threads are blocked
* until a thread has released all of its locks on the mutex.
*
* This particular implementation performs fewer safety checks. Like
* the FastLock implementation, any waiting caused by an acquire() request
* is not interruptable. This is so that the mutex can have the fastest
* response time for a time critical application while still having a good
* degree of reliability.
*
* TryEnterCriticalSection() does not work at all on some systems, so its
* not used.
*
*
* 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. If you define ZT_WIN9X, you'll get a version of the
* FastLock that uses the XCHG instruction
*/
class FastRecursiveLock : private NonCopyable {
// Add def for mingw32 or other non-ms compiler to align on 64-bit
// boundary
#pragma pack(push, 8)
LONG volatile _lock;
#pragma pack(pop)
LONG _count;
public:
/**
* Create a new FastRecursiveLock
*/
inline FastRecursiveLock() : _lock(0), _count(0) { }
/**
* Destroy FastLock
*/
inline ~FastRecursiveLock() {
assert(_lock == 0);
}
/**
* Lock the fast Lock, no error check.
*
* @exception None
*/
inline void acquire() {
DWORD id = ::GetCurrentThreadId();
// Take ownership if the lock is free or owned by the calling thread
do {
DWORD owner = (DWORD)::InterlockedCompareExchange(const_cast<LPLONG>(&_lock), id, 0);
if(owner == 0 || owner == id)
break;
::Sleep(0);
} while(1);
_count++;
}
/**
* Release the fast Lock, no error check.
*
* @exception None
*/
inline void release() {
if(--_count == 0)
::InterlockedExchange(const_cast<LPLONG>(&_lock), 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) {
DWORD id = ::GetCurrentThreadId();
DWORD owner = (DWORD)::InterlockedCompareExchange(const_cast<LPLONG>(&_lock), id, 0);
if(owner == 0 || owner == id) {
_count++;
return true;
}
return false;
}
}; /* FastRecursiveLock */
};
#endif
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