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#include "threads.h"
#include <time.h>
#include <errno.h>
#define sema_err (thrd_success - 1)
#define NSEC_PER_SEC ((time_t)1000000000L)
int sema_init(sema_t* sema, ssize_t value) {
int rv;
rv = mtx_init(&sema->__lock, mtx_plain);
if (rv != thrd_success) return rv;
rv = cnd_init(&sema->__cond);
if (rv != thrd_success) {
mtx_destroy(&sema->__lock);
return rv;
}
sema->__val = value;
return thrd_success;
}
int sema_get_value(sema_t* sema, ssize_t* p_value) {
int rv;
rv = mtx_lock(&sema->__lock);
if (rv != thrd_success) return rv;
*p_value = sema->__val;
return mtx_unlock(&sema->__lock);
}
int sema_up(sema_t* sema) {
return sema_up_many(sema, 1);
}
int sema_up_many(sema_t* sema, ssize_t n) {
int rv;
rv = mtx_lock(&sema->__lock);
if (rv != thrd_success) return rv;
sema->__val += n;
rv = mtx_unlock(&sema->__lock);
if (rv != thrd_success) return rv;
for (ssize_t i = 0; i < n; i++) {
rv = cnd_signal(&sema->__cond);
if (rv != thrd_success) return rv;
}
return thrd_success;
}
int sema_down(sema_t* sema) {
return sema_down_many(sema, 1);
}
int sema_down_many(sema_t* sema, ssize_t n) {
int rv;
rv = mtx_lock(&sema->__lock);
if (rv != thrd_success) return rv;
while (sema->__val < n) {
rv = cnd_wait(&sema->__cond, &sema->__lock);
if (rv != thrd_success) return rv;
}
sema->__val -= n;
return mtx_unlock(&sema->__lock);
}
int sema_try_down(sema_t* sema) {
return sema_try_down_many(sema, 1);
}
int sema_try_down_many(sema_t* sema, ssize_t n) {
int rv;
rv = mtx_lock(&sema->__lock);
if (rv != thrd_success) return rv;
if (sema->__val < n) {
rv = mtx_unlock(&sema->__lock);
if (rv != thrd_success) return rv;
errno = EAGAIN;
return sema_err;
}
sema->__val -= n;
return mtx_unlock(&sema->__lock);
}
int sema_down_timed(sema_t* sema, const struct timespec* time) {
return sema_down_many_timed(sema, time, 1);
}
static bool diff_timespec(
struct timespec* dst,
const struct timespec* src
) {
*dst = (struct timespec) {
.tv_sec = dst->tv_sec - src->tv_sec,
.tv_nsec = dst->tv_nsec - src->tv_nsec
};
if (dst->tv_nsec < 0) {
dst->tv_sec--;
dst->tv_nsec += NSEC_PER_SEC;
}
return dst->tv_sec > 0 || (dst->tv_sec == 0 && dst->tv_nsec > 0);
}
int sema_down_many_timed(sema_t* sema, const struct timespec* time, ssize_t n) {
int rv;
struct timespec start, end, remaining = *time;
timespec_get(&start, TIME_UTC);
rv = mtx_timedlock(&sema->__lock, &remaining);
if (rv != thrd_success) return rv;
timespec_get(&end, TIME_UTC);
diff_timespec(&end, &start);
if (!diff_timespec(&remaining, &end)) return thrd_timedout;
while (sema->__val < n) {
timespec_get(&start, TIME_UTC);
rv = cnd_timedwait(&sema->__cond, &sema->__lock, &remaining);
if (rv != thrd_success) return rv;
timespec_get(&end, TIME_UTC);
diff_timespec(&end, &start);
if (!diff_timespec(&remaining, &end)) return thrd_timedout;
}
sema->__val -= n;
return mtx_unlock(&sema->__lock);
}
void sema_destroy(sema_t* sema) {
cnd_destroy(&sema->__cond);
mtx_destroy(&sema->__lock);
}
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