px4-firmware/platforms/common/work_queue/dq_remfirst.c

/************************************************************
 * libc/queue/dq_remfirst.c
 *
 *   Copyright (C) 2007, 2011 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.
 *
 ************************************************************/

/************************************************************
 * Compilation Switches
 ************************************************************/

/************************************************************
 * Included Files
 ************************************************************/

#include <stddef.h>
#include <queue.h>

/************************************************************
 * Public Functions
 ************************************************************/

/************************************************************
 * Name: dq_remfirst
 *
 * Description:
 *   dq_remfirst removes 'node' from the head of 'queue'
 *
 ************************************************************/

dq_entry_t *dq_remfirst(dq_queue_t *queue)
{
	dq_entry_t *ret = queue->head;

	if (ret) {
		dq_entry_t *next = ret->flink;

		if (!next) {
			queue->head = NULL;
			queue->tail = NULL;

		} else {
			queue->head = next;
			next->blink = NULL;
		}

		ret->flink = NULL;
		ret->blink = NULL;
	}

	return ret;
}