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- /****************************************************************************
- * sched/mqueue/mq_receive.c
- *
- * Copyright (C) 2007, 2009, 2016-2017 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- * used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <sys/types.h>
- #include <stdbool.h>
- #include <errno.h>
- #include <mqueue.h>
- #include <debug.h>
- #include <nuttx/irq.h>
- #include <nuttx/arch.h>
- #include <nuttx/mqueue.h>
- #include <nuttx/cancelpt.h>
- #include "mqueue/mqueue.h"
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: nxmq_receive
- *
- * Description:
- * This function receives the oldest of the highest priority messages
- * from the message queue specified by "mqdes." This is an internal OS
- * interface. It is functionally equivalent to mq_receive except that:
- *
- * - It is not a cancellation point, and
- * - It does not modify the errno value.
- *
- * See comments with mq_receive() for a more complete description of the
- * behavior of this function
- *
- * Input Parameters:
- * mqdes - Message Queue Descriptor
- * msg - Buffer to receive the message
- * msglen - Size of the buffer in bytes
- * prio - If not NULL, the location to store message priority.
- *
- * Returned Value:
- * This is an internal OS interface and should not be used by applications.
- * It follows the NuttX internal error return policy: Zero (OK) is
- * returned on success. A negated errno value is returned on failure.
- * (see mq_receive() for the list list valid return values).
- *
- ****************************************************************************/
- ssize_t nxmq_receive(mqd_t mqdes, FAR char *msg, size_t msglen,
- FAR unsigned int *prio)
- {
- FAR struct mqueue_msg_s *mqmsg;
- irqstate_t flags;
- ssize_t ret;
- DEBUGASSERT(up_interrupt_context() == false);
- /* Verify the input parameters and, in case of an error, set
- * errno appropriately.
- */
- ret = nxmq_verify_receive(mqdes, msg, msglen);
- if (ret < 0)
- {
- return ret;
- }
- /* Get the next message from the message queue. We will disable
- * pre-emption until we have completed the message received. This
- * is not too bad because if the receipt takes a long time, it will
- * be because we are blocked waiting for a message and pre-emption
- * will be re-enabled while we are blocked
- */
- sched_lock();
- /* Furthermore, nxmq_wait_receive() expects to have interrupts disabled
- * because messages can be sent from interrupt level.
- */
- flags = enter_critical_section();
- /* Get the message from the message queue */
- ret = nxmq_wait_receive(mqdes, &mqmsg);
- leave_critical_section(flags);
- /* Check if we got a message from the message queue. We might
- * not have a message if:
- *
- * - The message queue is empty and O_NONBLOCK is set in the mqdes
- * - The wait was interrupted by a signal
- */
- if (ret >= 0)
- {
- DEBUGASSERT(mqmsg != NULL);
- ret = nxmq_do_receive(mqdes, mqmsg, msg, prio);
- }
- sched_unlock();
- return ret;
- }
- /****************************************************************************
- * Name: mq_receive
- *
- * Description:
- * This function receives the oldest of the highest priority messages
- * from the message queue specified by "mqdes." If the size of the
- * buffer in bytes (msglen) is less than the "mq_msgsize" attribute of
- * the message queue, mq_receive will return an error. Otherwise, the
- * selected message is removed from the queue and copied to "msg."
- *
- * If the message queue is empty and O_NONBLOCK was not set,
- * mq_receive() will block until a message is added to the message
- * queue. If more than one task is waiting to receive a message, only
- * the task with the highest priority that has waited the longest will
- * be unblocked.
- *
- * If the queue is empty and O_NONBLOCK is set, ERROR will be returned.
- *
- * Input Parameters:
- * mqdes - Message Queue Descriptor
- * msg - Buffer to receive the message
- * msglen - Size of the buffer in bytes
- * prio - If not NULL, the location to store message priority.
- *
- * Returned Value:
- * One success, the length of the selected message in bytes is returned.
- * On failure, -1 (ERROR) is returned and the errno is set appropriately:
- *
- * EAGAIN The queue was empty, and the O_NONBLOCK flag was set
- * for the message queue description referred to by 'mqdes'.
- * EPERM Message queue opened not opened for reading.
- * EMSGSIZE 'msglen' was less than the maxmsgsize attribute of the
- * message queue.
- * EINTR The call was interrupted by a signal handler.
- * EINVAL Invalid 'msg' or 'mqdes'
- *
- ****************************************************************************/
- ssize_t mq_receive(mqd_t mqdes, FAR char *msg, size_t msglen,
- FAR unsigned int *prio)
- {
- int ret;
- /* mq_receive() is a cancellation point */
- (void)enter_cancellation_point();
- /* Let nxmq_receive do all of the work */
- ret = nxmq_receive(mqdes, msg, msglen, prio);
- if (ret < 0)
- {
- set_errno(-ret);
- ret = ERROR;
- }
- leave_cancellation_point();
- return ret;
- }
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