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/*------------------------------------------------------------------------
* Copyright 2007-2009 (c) Jeff Brown <spadix@users.sourceforge.net>
*
* This file is part of the ZBar Bar Code Reader.
*
* The ZBar Bar Code Reader is free software; you can redistribute it
* and/or modify it under the terms of the GNU Lesser Public License as
* published by the Free Software Foundation; either version 2.1 of
* the License, or (at your option) any later version.
*
* The ZBar Bar Code Reader 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 Lesser Public License for more details.
*
* You should have received a copy of the GNU Lesser Public License
* along with the ZBar Bar Code Reader; if not, write to the Free
* Software Foundation, Inc., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301 USA
*
* http://sourceforge.net/projects/zbar
*------------------------------------------------------------------------*/
#include <assert.h>
#include "processor.h"
/* the processor api lock is a recursive mutex with added capabilities
* to completely drop all lock levels before blocking and atomically
* unblock a waiting set. the lock is implemented using a variation
* of the "specific notification pattern" [cargill], which makes it
* easy to provide these features across platforms with consistent,
* predictable semantics. probably overkill, but additional overhead
* associated with this mechanism should fall in the noise, as locks
* are only exchanged O(frame/image)
*
* [cargill]
* http://www.profcon.com/profcon/cargill/jgf/9809/SpecificNotification.html
*/
static inline proc_waiter_t *proc_waiter_queue(zbar_processor_t *proc)
{
proc_waiter_t *waiter = proc->free_waiter;
if (waiter) {
proc->free_waiter = waiter->next;
waiter->events = 0;
} else {
waiter = calloc(1, sizeof(proc_waiter_t));
_zbar_event_init(&waiter->notify);
}
waiter->next = NULL;
waiter->requester = _zbar_thread_self();
if (proc->wait_head)
proc->wait_tail->next = waiter;
else
proc->wait_head = waiter;
proc->wait_tail = waiter;
return (waiter);
}
static inline proc_waiter_t *proc_waiter_dequeue(zbar_processor_t *proc)
{
proc_waiter_t *prev = proc->wait_next, *waiter;
if (prev)
waiter = prev->next;
else
waiter = proc->wait_head;
while (waiter && (waiter->events & EVENTS_PENDING)) {
prev = waiter;
proc->wait_next = waiter;
waiter = waiter->next;
}
if (waiter) {
if (prev)
prev->next = waiter->next;
else
proc->wait_head = waiter->next;
if (!waiter->next)
proc->wait_tail = prev;
waiter->next = NULL;
proc->lock_level = 1;
proc->lock_owner = waiter->requester;
}
return (waiter);
}
static inline void proc_waiter_release(zbar_processor_t *proc,
proc_waiter_t *waiter)
{
if (waiter) {
waiter->next = proc->free_waiter;
proc->free_waiter = waiter;
}
}
int _zbar_processor_lock(zbar_processor_t *proc)
{
proc_waiter_t *waiter;
if (!proc->lock_level) {
proc->lock_owner = _zbar_thread_self();
proc->lock_level = 1;
return (0);
}
if (_zbar_thread_is_self(proc->lock_owner)) {
proc->lock_level++;
return (0);
}
waiter = proc_waiter_queue(proc);
_zbar_event_wait(&waiter->notify, &proc->mutex, NULL);
assert(proc->lock_level == 1);
assert(_zbar_thread_is_self(proc->lock_owner));
proc_waiter_release(proc, waiter);
return (0);
}
int _zbar_processor_unlock(zbar_processor_t *proc, int all)
{
assert(proc->lock_level > 0);
assert(_zbar_thread_is_self(proc->lock_owner));
if (all)
proc->lock_level = 0;
else
proc->lock_level--;
if (!proc->lock_level) {
proc_waiter_t *waiter = proc_waiter_dequeue(proc);
if (waiter)
_zbar_event_trigger(&waiter->notify);
}
return (0);
}
void _zbar_processor_notify(zbar_processor_t *proc, unsigned events)
{
proc_waiter_t *waiter;
proc->wait_next = NULL;
for (waiter = proc->wait_head; waiter; waiter = waiter->next)
waiter->events =
((waiter->events & ~events) | (events & EVENT_CANCELED));
if (!proc->lock_level) {
waiter = proc_waiter_dequeue(proc);
if (waiter)
_zbar_event_trigger(&waiter->notify);
}
}
static inline int proc_wait_unthreaded(zbar_processor_t *proc,
proc_waiter_t *waiter,
zbar_timer_t *timeout)
{
int rc;
int blocking = proc->streaming && zbar_video_get_fd(proc->video) < 0;
_zbar_mutex_unlock(&proc->mutex);
rc = 1;
while (rc > 0 && (waiter->events & EVENTS_PENDING)) {
int reltime;
/* FIXME lax w/the locking (though shouldn't matter...) */
if (blocking) {
zbar_image_t *img = zbar_video_next_image(proc->video);
if (!img) {
rc = -1;
break;
}
/* FIXME reacquire API lock! (refactor w/video thread?) */
_zbar_mutex_lock(&proc->mutex);
_zbar_process_image(proc, img);
zbar_image_destroy(img);
_zbar_mutex_unlock(&proc->mutex);
}
reltime = _zbar_timer_check(timeout);
if (blocking && (reltime < 0 || reltime > MAX_INPUT_BLOCK))
reltime = MAX_INPUT_BLOCK;
rc = _zbar_processor_input_wait(proc, NULL, reltime);
}
_zbar_mutex_lock(&proc->mutex);
return (rc);
}
int _zbar_processor_wait(zbar_processor_t *proc, unsigned events,
zbar_timer_t *timeout)
{
int save_level;
proc_waiter_t *waiter;
int rc;
_zbar_mutex_lock(&proc->mutex);
save_level = proc->lock_level;
waiter = proc_waiter_queue(proc);
waiter->events = events & EVENTS_PENDING;
_zbar_processor_unlock(proc, 1);
if (proc->threaded)
rc = _zbar_event_wait(&waiter->notify, &proc->mutex, timeout);
else
rc = proc_wait_unthreaded(proc, waiter, timeout);
if (rc <= 0 || !proc->threaded) {
/* reacquire api lock */
waiter->events &= EVENT_CANCELED;
proc->wait_next = NULL;
if (!proc->lock_level) {
proc_waiter_t *w = proc_waiter_dequeue(proc);
assert(w == waiter);
} else
_zbar_event_wait(&waiter->notify, &proc->mutex, NULL);
}
if (rc > 0 && (waiter->events & EVENT_CANCELED))
rc = -1;
assert(proc->lock_level == 1);
assert(_zbar_thread_is_self(proc->lock_owner));
proc->lock_level = save_level;
proc_waiter_release(proc, waiter);
_zbar_mutex_unlock(&proc->mutex);
return (rc);
}
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