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/*
* Copyright (c) 2008,2009 Zmanda, Inc. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 as published
* by the Free Software Foundation.
*
* 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, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Contact information: Zmanda Inc., 465 S. Mathilda Ave., Suite 300
* Sunnyvale, CA 94085, USA, or: http://www.zmanda.com
*/
/* GLib does not provide semaphores, which are useful in queue.c.
So, we implement it here. */
#include <glib.h>
#ifndef SEMAPHORE_H
typedef struct {
int value;
GMutex *mutex;
GCond * decrement_cond;
GCond * zero_cond;
} amsemaphore_t;
/* Create a new semaphore object with the given value.
*
* @param value: new value
* @returns: newly allocated amsemaphore_t
*/
amsemaphore_t* amsemaphore_new_with_value(int value);
/* Shortcut to make a new semaphore with value 1.
*/
#define amsemaphore_new() amsemaphore_new_with_value(1)
/* Free a semaphore allocated by amsemaphore_with_new_value(). Be sure the
* semaphore is no longer in use by any threads.
*
* @param sem: the semaphore to free
*/
void amsemaphore_free(amsemaphore_t *sem);
/* Increment the value of the semaphore by incr. This corresponds to
* Dijkstra's V(), or the typical semaphore's release().
*
* This function will not block, but may wake other threads waiting
* on amsemaphore_decrement().
*
* @param sem: the semaphore
* @param incr: added to the semaphore's value
*/
void amsemaphore_increment(amsemaphore_t *sem, unsigned int incr);
/* Shortcut to increment the semaphore by 1.
*/
#define amsemaphore_up(semaphore) amsemaphore_increment(semaphore,1)
/* Decrement the value of the semaphore by incr. If this operation
* would make the semaphore negative, block until the semaphore
* value is large enough, then perform the decerement operation. Threads
* waiting on amsemaphore_wait_empty() may be awakened if the value
* reaches 0.
*
* @param sem: the semaphore
* @param decr: subtracted from the semaphore's value
*/
void amsemaphore_decrement(amsemaphore_t *sem, unsigned int decr);
/* Shortcut to decrement the semaphore by 1.
*/
#define amsemaphore_down(semaphore) amsemaphore_decrement(semaphore, 1)
/* Increment or decrement (with a negative incr) the value without
* blocking. Threads waiting on amsemaphore_decrement() or
* amsemaphore_wait_empty() will be awakened if necessary.
*
* @param sem: the semaphore
* @param incr: added to the semaphore's value
*/
void amsemaphore_force_adjust(amsemaphore_t *sem, int incr);
/* Set the semaphore to a given value without blocking. Threads
* waiting on amsemaphore_decrement() or amsemaphore_wait_empty()
* will be awakened if necessary.
*
* @param sem: the semaphore
* @param value: the new value
*/
void amsemaphore_force_set(amsemaphore_t *sem, int value);
/* Block until the semaphore's value is zero.
*
* @param sem: the semaphore
*/
void amsemaphore_wait_empty(amsemaphore_t *sem);
#endif /* SEMAPHORE_H */
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