/**************************************************************************** * sched/mqueue/mq_receive.c * * Copyright (C) 2007, 2009, 2016-2017 Gregory Nutt. All rights reserved. * Author: Gregory Nutt * * 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 #include #include #include #include #include #include #include #include #include #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 cancellaction 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 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 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; }