source: mainline/generic/include/fifo.h@ 86c9e37

/*
 * Copyright (C) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - 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.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
 */

/*
 * This implementation of FIFO stores values in a statically
 * allocated array created on each FIFO's initialization.
 * As such, these FIFOs have upper bound on number of values
 * they can store. Push and pop operations are done via accessing
 * the array through head and tail indices. Because of better
 * operation ordering in fifo_pop(), the access policy for these
 * two indices is to 'increment (mod size of FIFO) and use'.
 */

#ifndef __FIFO_H__
#define __FIFO_H__

#include <typedefs.h>

/** Create and initialize FIFO.
 *
 * @param name Name of FIFO.
 * @param t Type of values stored in FIFO.
 * @param itms Number of items that can be stored in FIFO.
 */
#define FIFO_INITIALIZE(name, t, itms)                  \
        struct {                                        \
                t fifo[(itms)];                         \
                count_t items;                          \
                index_t head;                           \
                index_t tail;                           \
        } name = {                                      \
                .items = (itms),                        \
                .head = 0,                              \
                .tail = 0                               \
        }

/** Pop value from head of FIFO.
 *
 * @param name FIFO name.
 *
 * @return Leading value in FIFO.
 */
#define fifo_pop(name) \
        name.fifo[name.head = (name.head + 1) % name.items]

/** Push value to tail of FIFO.
 *
 * @param name FIFO name.
 * @param value Value to be appended to FIFO.
 *
 */
#define fifo_push(name, value) \
        name.fifo[name.tail = (name.tail + 1) % name.items] = (value) 

#endif