/* -*- mode: c++; c-basic-offset: 4; tab-width: 4; indent-tabs-mode: t -*-
 * vim: ts=4 sw=4 noet ai cindent syntax=cpp
 *
 * Conky, a system monitor, based on torsmo
 *
 * Please see COPYING for details
 *
 * Copyright (C) 2010 Pavel Labath et al.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 */

#ifndef SEMAPHORE_HH
#define SEMAPHORE_HH

#include <cerrno>
#include <cstdlib>
#include <cstring>
#include <stdexcept>

#if defined(__APPLE__) && defined(__MACH__)

/*
 *  On Darwin, unnamed semaphores are not supported!
 *  The only close equivalent to unnamed semaphores is using
 *      GCD!
 */

#include <dispatch/dispatch.h>

class semaphore {
	dispatch_semaphore_t    sem;
    
    	semaphore(const semaphore &) = delete;
    	semaphore& operator=(const semaphore &) = delete;
public:
    	semaphore(unsigned int value = 0) throw(std::logic_error)
    	{
        	sem = dispatch_semaphore_create(value);
        
        	if (!sem)
            		throw std::logic_error(strerror(errno));
    	}
    
    	~semaphore() throw()
    	{
        	dispatch_release(sem);
    	}
    	void post() throw(std::overflow_error)
    	{
        	dispatch_semaphore_signal(sem);
   	}
    
    	void wait() throw()
    	{
        	dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
    	}
    
    	bool trywait() throw()
    	{
        	/* XXX Quick patch */
#define DISPATCH_EAGAIN 49
        
        	int ret = dispatch_semaphore_wait(sem, DISPATCH_TIME_NOW);
        
        	while (ret > 0)
        	{
            		if(ret == DISPATCH_EAGAIN)
                		return false;
            		else if(errno != EINTR)
                	abort();
        	}
        	return true;
    	}
};

#else

#include <semaphore.h>

class semaphore {
    	sem_t sem;
    
    	semaphore(const semaphore &) = delete;
   	semaphore& operator=(const semaphore &) = delete;
public:
    	semaphore(unsigned int value = 0) throw(std::logic_error)
    	{
        	if(sem_init(&sem, 0, value))
            		throw std::logic_error(strerror(errno));
    	}
    
    	~semaphore() throw()
    	{ sem_destroy(&sem); }
    
    	void post() throw(std::overflow_error)
    	{
        	if(sem_post(&sem))
            	throw std::overflow_error(strerror(errno));
    	}
    
    	void wait() throw()
    	{
        	while(sem_wait(&sem)) {
            		if(errno != EINTR)
                	abort();
        	}
    	}
    
    	bool trywait() throw()
    	{
        	while(sem_trywait(&sem)) {
            
            	if(errno == EAGAIN)
                	return false;
            	else if(errno != EINTR)
                	abort();
        	}
      		return true;
    	}
};

#endif /* defined(__APPLE__) && defined(__MACH__) */

#endif