sem_init函数的返回值是什么

应该这样

#define CHECK(_sem) (sem_init(&(_sem)->sem, (pshared), (value)) == 0) ? ((_sem)->valid = true, 0) : ((_sem)->valid = false, -1)

然后使用的地方为

ret = CHECK(_sem)

也就是说，sem_init返回0时，_sem->valid被设置成true, ret被设置为0,

sem_init返回非0时，_sem->valid被设置成false, ret被设置为-1

#include <fcntl.h>

#include <semaphore.h>

#include <pthread.h>

#include <sys/stat.h>#define LENTH 8typedef int Ttypedef struct cycle

{

T data[LENTH]

int head

int tail

sem_t *mutex

sem_t *db

int reader

} circularint init_queue(circular *queue)

int is_empty(circular queue)

int is_full(circular queue)

int insert(circular queue, const T data)

int popout(circular queue, T *data)

int queue_lenth(circular queue)

int read_queue(int tag, T *data, circular queue)

int close_queue(circular *queue)int init_queue(circular *queue)

{

queue->head = 0

queue->tail = 0

queue->mutex = sem_open("read", O_RDWR | O_CREAT, 0644, 0)

queue->db = sem_open("write", O_RDWR | O_CREAT, 0644, 0)

sem_init(queue->mutex, 0, 1)

sem_init(queue->db, 0, 1)

queue->reader = 0

return 0

}int is_empty(circular queue)

{

int ret

sem_wait(queue.mutex)

queue.reader++

if(queue.reader == 1)

sem_wait(queue.db)

sem_post(queue.mutex)

//临界区

ret = (queue.head == queue.tail)

//临界区

sem_wait(queue.mutex)

queue.reader--

if(queue.reader == 0)

sem_post(queue.mutex)

return ret

}int is_full(circular queue)

{

int ret

sem_wait(queue.mutex)

queue.reader++

if(queue.reader == 1)

sem_wait(queue.db)

sem_post(queue.mutex)

//临界区

ret = (queue.head == (queue.tail + 1) % LENTH)

//临界区

sem_wait(queue.mutex)

queue.reader--

if(queue.reader == 0)

sem_post(queue.mutex)

return ret

}int insert(circular queue, const T data)

{

int ret = 0

sem_wait(queue.db)

//临界区

if(is_empty(queue))

ret = -1

queue.data[queue.tail] = data

queue.tail = (queue.tail + 1) % LENTH

sem_post(queue.db)

//临界区

return ret

}int popout(circular queue, T *data)

{

int ret = 0

sem_wait(queue.db)

//临界区

if(is_full(queue))

ret = -1

*data = queue.data[queue.head]

queue.head = (queue.head + 1) % LENTH

//临界区

sem_post(queue.db)

return ret

}int queue_lenth(circular queue)

{

int ret

sem_wait(queue.mutex)

queue.reader++

if(queue.reader == 1)

sem_wait(queue.db)

sem_post(queue.mutex)

//临界区

ret = (queue.tail - queue.head + LENTH) % LENTH

//临界区

sem_wait(queue.mutex)

queue.reader--

if(queue.reader == 0)

sem_post(queue.mutex)

return ret

}int read_queue(int tag, T *data, circular queue)

{

int ret = 0

sem_wait(queue.mutex)

queue.reader++

if(queue.reader == 1)

sem_wait(queue.db)

sem_post(queue.mutex)

//临界区

if(tag >= queue_lenth(queue))

ret = -1

*data = queue.data[queue.head + tag]

//临界区

sem_wait(queue.mutex)

queue.reader--

if(queue.reader == 0)

sem_post(queue.mutex)

return ret

}int close_queue(circular *queue)

{

sem_destroy(queue->mutex)

sem_destroy(queue->db)

return 0

}

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