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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 <pthread.h>
#include <errno.h>
#include <assert.h>
namespace ZThread {
/**
* @class FastRecursiveLock
*
* @author Eric Crahen <http://www.code-foo.com>
* @date <2003-07-16T23:28:37-0400>
* @version 2.2.0
*
* This is an implementation of a FastRecursiveLock for any vannila
* POSIX system. It is based on a condition variable and a mutex;
* because of this it is important to not that its waiting properties
* are not the same as other mutex implementations that generally
* based on spin locks. Under high contention, this implementation may
* be preferable to a spin lock, although refactoring the design of
* code that puts a mutex under alot of preasure may be worth investigating.
*/
class FastRecursiveLock : private NonCopyable {
//! Serialize state
pthread_mutex_t _mtx;
//! Wait for lock
pthread_cond_t _cond;
//! Owner
pthread_t _owner;
//! Count
volatile unsigned int _count;
public:
inline FastRecursiveLock() : _owner(0), _count(0) {
pthread_mutex_init(&_mtx, 0);
if(pthread_cond_init(&_cond, 0) != 0) {
assert(0);
}
}
inline ~FastRecursiveLock() {
pthread_mutex_destroy(&_mtx);
if(pthread_cond_destroy(&_cond) != 0) {
assert(0);
}
}
inline void acquire() {
pthread_t self = pthread_self();
pthread_mutex_lock(&_mtx);
// If the caller does not own the lock, wait until there is no owner
if(_owner != 0 && !pthread_equal(_owner, self)) {
int status = 0;
do { // ignore signals
status = pthread_cond_wait(&_cond, &_mtx);
} while(status == EINTR && _owner == 0);
}
_owner = self;
_count++;
pthread_mutex_unlock(&_mtx);
}
inline bool tryAcquire(unsigned long timeout=0) {
pthread_t self = pthread_self();
pthread_mutex_lock(&_mtx);
// If the caller owns the lock, or there is no owner update the count
bool success = (_owner == 0 || pthread_equal(_owner, self));
if(success) {
_owner = self;
_count++;
}
pthread_mutex_unlock(&_mtx);
return success;
}
inline void release() {
assert(pthread_equal(_owner, pthread_self()));
pthread_mutex_lock(&_mtx);
if(--_count == 0) {
_owner = 0;
pthread_cond_signal(&_cond);
}
pthread_mutex_unlock(&_mtx);
}
}; /* FastRecursiveLock */
} // namespace ZThread
#endif
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