#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include "utils.h"
#include "mysem.h"
Semaphore *make_semaphore(int value)
{
Semaphore *semaphore = check_malloc(sizeof(Semaphore));
semaphore->value = value;
semaphore->wakeups = 0;
semaphore->mutex = make_mutex();
semaphore->cond = make_cond();
return semaphore;
}
void semaphore_wait(Semaphore *semaphore)
{
mutex_lock(semaphore->mutex);
semaphore->value--;
if (semaphore->value < 0) {
do {
cond_wait(semaphore->cond, semaphore->mutex);
} while (semaphore->wakeups < 1);
semaphore->wakeups--;
}
mutex_unlock(semaphore->mutex);
}
void semaphore_signal(Semaphore *semaphore)
{
mutex_lock(semaphore->mutex);
semaphore->value++;
if (semaphore->value <= 0) {
semaphore->wakeups++;
cond_signal(semaphore->cond);
}
mutex_unlock(semaphore->mutex);
}
