/************************************************************************
* sched/mq_receive.c
*
* Copyright (C) 2007, 2009 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/arch.h>
#include "mq_internal.h"
/************************************************************************
* Pre-processor Definitions
************************************************************************/
/************************************************************************
* Private Type Declarations
************************************************************************/
/************************************************************************
* Global Variables
************************************************************************/
/************************************************************************
* Private Variables
************************************************************************/
/************************************************************************
* Private Functions
************************************************************************/
/************************************************************************
* Public Functions
************************************************************************/
/************************************************************************
* 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.
*
* 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.
*
* Return 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'
*
* Assumptions:
*
************************************************************************/
ssize_t mq_receive(mqd_t mqdes, void *msg, size_t msglen, int *prio)
{
FAR mqmsg_t *mqmsg;
irqstate_t saved_state;
ssize_t ret = ERROR;
DEBUGASSERT(up_interrupt_context() == false);
/* Verify the input parameters and, in case of an error, set
* errno appropriately.
*/
if (mq_verifyreceive(mqdes, msg, msglen) != OK)
{
return ERROR;
}
/* Get the next mesage 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, mq_waitreceive() expects to have interrupts disabled
* because messages can be sent from interrupt level.
*/
saved_state = irqsave();
/* Get the message from the message queue */
mqmsg = mq_waitreceive(mqdes);
irqrestore(saved_state);
/* 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 (mqmsg)
{
ret = mq_doreceive(mqdes, mqmsg, msg, prio);
}
sched_unlock();
return ret;
}
