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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libc/] [sys/] [linux/] [mq_receive.c] - Rev 262
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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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