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/* Copyright 2002, Red Hat Inc. */
#include <mqueue.h>
#include <fcntl.h>
#include <errno.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <string.h>
#define _LIBC 1
#include <sys/lock.h>
#undef _LIBC
#include "mqlocal.h"
__LOCK_INIT(static, mq_rdbuf_lock);
ssize_t
mq_receive (mqd_t msgid, char *msg, size_t msg_len, unsigned int *msg_prio)
{
struct libc_mq *info;
struct sembuf sb2 = {2, 1, 0};
struct sembuf sb3 = {3, -1, IPC_NOWAIT};
struct sembuf sb5 = {5, 1, IPC_NOWAIT};
ssize_t num_bytes;
int ipcflag;
info = __find_mq (msgid);
if (info == NULL || (info->oflag & O_ACCMODE) == O_WRONLY)
{
errno = EBADF;
return -1;
}
if (msg_len < info->attr->mq_msgsize)
{
errno = EMSGSIZE;
return -1;
}
__lock_acquire (mq_rdbuf_lock);
ipcflag = (info->attr->mq_flags & O_NONBLOCK) ? IPC_NOWAIT : 0;
semop (info->semid, &sb5, 1); /* increase number of readers */
num_bytes = msgrcv (info->msgqid, info->rdbuf, msg_len, -MQ_PRIO_MAX, ipcflag);
sb5.sem_op = -1;
semop (info->semid, &sb5, 1); /* decrease number of readers */
if (num_bytes != (ssize_t)-1)
{
semop (info->semid, &sb2, 1); /* add one to messages left to write */
semop (info->semid, &sb3, 1); /* subtract one from messages to read */
memcpy (msg, info->rdbuf->text, num_bytes);
if (msg_prio != NULL)
*msg_prio = MQ_PRIO_MAX - info->rdbuf->type;
}
__lock_release (mq_rdbuf_lock);
return num_bytes;
}
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