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/*
SuperCollider real time audio synthesis system
Copyright (c) 2002 James McCartney. All rights reserved.
http://www.audiosynth.com
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 2 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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "SC_SyncCondition.h"
SC_SyncCondition::SC_SyncCondition()
: read(0), write(0)
{
// the mutex is only for pthread_cond_wait, which requires it.
// since there is only supposed to be one signaller and one waiter
// there is nothing to mutually exclude.
pthread_mutex_init (&mutex, NULL);
pthread_cond_init (&available, NULL);
}
SC_SyncCondition::~SC_SyncCondition()
{
pthread_mutex_destroy (&mutex);
pthread_cond_destroy (&available);
}
void SC_SyncCondition::WaitEach()
{
// waits if it has caught up.
// not very friendly, may be trying in vain to keep up.
pthread_mutex_lock (&mutex);
while (read == write) {
pthread_cond_wait (&available, &mutex);
}
++read;
pthread_mutex_unlock (&mutex);
}
void SC_SyncCondition::WaitOnce()
{
// waits if not signaled since last time.
// if only a little late then can still go.
int writeSnapshot;
pthread_mutex_lock (&mutex);
writeSnapshot = write;
while (read == writeSnapshot) {
pthread_cond_wait (&available, &mutex);
}
read = writeSnapshot;
pthread_mutex_unlock (&mutex);
}
void SC_SyncCondition::WaitNext()
{
// will wait for the next signal after the read = write statement
// this is the friendliest to other tasks, because if it is
// late upon entry, then it has to lose a turn.
pthread_mutex_lock (&mutex);
read = write;
while (read == write) {
pthread_cond_wait (&available, &mutex);
}
pthread_mutex_unlock (&mutex);
}
void SC_SyncCondition::Signal()
{
++write;
pthread_cond_signal (&available);
}
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