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