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/*
* condvar.c
*
* Description:
* This translation unit implements condition variables and their primitives.
*/
#include "pthread.h"
int
pthread_condattr_init(pthread_condattr_t *attr)
{
return (attr == NULL) ? EINVAL : 0;
}
int
pthread_condattr_destroy(pthread_condattr_t *attr)
{
return (attr == NULL) ? EINVAL : 0;
}
int
pthread_condattr_setpshared(pthread_condattr_t *attr,
int pshared)
{
return (attr == NULL) ? EINVAL : ENOSYS;
}
int
pthread_condattr_getpshared(pthread_condattr_t *attr,
int *pshared)
{
return (attr == NULL) ? EINVAL : ENOSYS;
}
int
pthread_cond_init(pthread_cond_t *cv, const pthread_condattr_t *attr)
{
/* Ensure we have a valid cond_t variable. */
if (cv == NULL)
{
return EINVAL;
}
/* Initialize the count to 0. */
cv->waiters_count = 0;
/* Initialize the "mutex". */
pthread_mutex_init(cv->waiters_count_lock);
/* Create an auto-reset event. */
cv->events[SIGNAL] = CreateEvent (NULL, /* no security */
FALSE, /* auto-reset event */
FALSE, /* non-signaled initially */
NULL); /* unnamed */
/* Create a manual-reset event. */
cv->events[BROADCAST] = CreateEvent (NULL, /* no security */
TRUE, /* manual-reset */
FALSE, /* non-signaled initially */
NULL); /* unnamed */
return 0;
}
/* This is an internal routine that allows the functions `pthread_cond_wait' and
`pthread_cond_timedwait' to share implementations. The `abstime'
parameter to this function is in millisecond units (or INFINITE). */
static int
cond_wait(pthread_cond_t *cv, pthread_mutex_t *mutex, DWORD abstime)
{
int result, last_waiter;
/* Ensure we have a valid cond_t variable. */
if (cv == NULL)
{
return EINVAL;
}
/* Avoid race conditions. */
EnterCriticalSection (&cv->waiters_count_lock);
cv->waiters_count_++;
LeaveCriticalSection (&cv->waiters_count_lock);
/* It's okay to release the mutex here since Win32 manual-reset
events maintain state when used with SetEvent(). This avoids the
"lost wakeup" bug. */
pthread_mutex_unlock(mutex);
/* Wait for either event to become signaled due to
pthread_cond_signal() being called or pthread_cond_broadcast()
being called. */
result = WaitForMultipleObjects (2, ev->events, FALSE, abstime);
EnterCriticalSection (&cv->waiters_count_lock);
cv->waiters_count--;
last_waiter = cv->waiters_count == 0;
LeaveCriticalSection (&cv->waiters_count_lock);
/* Some thread called pthread_cond_broadcast(). */
if ((result = WAIT_OBJECT_0 + BROADCAST) && last_waiter)
{
/* We're the last waiter to be notified, so reset the manual
event. */
ResetEvent(cv->events[BROADCAST]);
}
/* Reacquire the mutex. */
pthread_mutex_lock(mutex);
return 0;
}
int
pthread_cond_wait(pthread_cond_t *cv,
pthread_mutex_t *mutex)
{
return cond_wait(cv, mutex, INFINITE);
}
/* Assume that our configure script will test for the existence of
`struct timespec' and define it according to POSIX if it isn't
found. This will enable people to use this implementation
without necessarily needing Cygwin32. */
int
pthread_cond_timedwait(pthread_cond_t *cv,
pthread_mutex_t *mutex,
const struct timespec *abstime)
{
DWORD msecs;
/* Calculate the number of milliseconds in abstime. */
msecs = abstime->tv_sec * 1000;
msecs += abstime->tv_nsec / 1000000;
return cond_wait(cv, mutex, msecs);
}
int
pthread_cond_broadcast (pthread_cond_t *cv)
{
int have_waiters;
/* Ensure we have a valid cond_t variable. */
if (cv == NULL)
{
return EINVAL;
}
/* Avoid race conditions. */
EnterCriticalSection (&cv->waiters_count_lock_);
have_waiters = (cv->waiters_count > 0);
LeaveCriticalSection (&cv->waiters_count_lock_);
if (have_waiters) {
SetEvent(cv->events[BROADCAST]);
}
return 0;
}
int
pthread_cond_signal (pthread_cond_t *cv)
{
int have_waiters;
/* Ensure we have a valid cond_t variable. */
if (cv == NULL)
{
return EINVAL;
}
/* Avoid race conditions. */
EnterCriticalSection (&cv->waiters_count_lock);
have_waiters = (cv->waiters_count > 0);
LeaveCriticalSection (&cv->waiters_count_lock);
if (have_waiters) {
SetEvent(cv->events[SIGNAL]);
}
return 0;
}
int
pthread_cond_destroy(pthread_cond_t *cv)
{
if (cv == NULL)
{
return EINVAL;
}
return pthread_mutex_destroy(cv->waiters_count_lock);
}
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