/*
 * OXT - OS eXtensions for boosT
 * Provides important functionality necessary for writing robust server software.
 *
 * Copyright (c) 2010 Phusion
 *
 * 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.
 */

#include <boost/noncopyable.hpp>
#include <pthread.h>
#include <errno.h>
#include "../macros.hpp"

/*
 * Implementation of a spin lock using POSIX pthread spin locks.
 *
 * See spin_lock_gcc_x86.hpp for API documentation.
 */

namespace oxt {

class spin_lock {
private:
	pthread_spinlock_t spin;

public:
	class scoped_lock: boost::noncopyable {
	private:
		spin_lock &l;
		
	public:
		scoped_lock(spin_lock &lock): l(lock) {
			l.lock();
		}
		
		~scoped_lock() {
			l.unlock();
		}
	};

	spin_lock() {
		int ret;
		do {
			ret = pthread_spin_init(&spin, PTHREAD_PROCESS_PRIVATE);
		} while (ret == EINTR);
		if (ret != 0) {
			throw boost::thread_resource_error(ret, "Cannot initialize a spin lock");
		}
	}
	
	~spin_lock() {
		int ret;
		do {
			ret = pthread_spin_destroy(&spin);
		} while (ret == EINTR);
	}
	
	void lock() {
		int ret;
		do {
			ret = pthread_spin_lock(&spin);
		} while (OXT_UNLIKELY(ret == EINTR));
		if (OXT_UNLIKELY(ret != 0)) {
			throw boost::thread_resource_error(ret, "Cannot lock spin lock");
		}
	}

	void unlock() {
		int ret;
		do {
			ret = pthread_spin_unlock(&spin);
		} while (OXT_UNLIKELY(ret == EINTR));
		if (OXT_UNLIKELY(ret != 0)) {
			throw boost::thread_resource_error(ret, "Cannot unlock spin lock");
		}
	}

	bool try_lock() {
		int ret;
		do {
			ret = pthread_spin_trylock(&spin);
		} while (OXT_UNLIKELY(ret == EINTR));
		if (ret == 0) {
			return true;
		} else if (ret == EBUSY) {
			return false;
		} else {
			throw boost::thread_resource_error(ret, "Cannot lock spin lock");
		}
	}
};

} // namespace oxt

