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/*

 * 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 an array

 * (static or dynamic). 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 <malloc.h>

typedef unsigned long fifo_count_t;

typedef unsigned long fifo_index_t;

#define FIFO_CREATE_STATIC(name, t, itms)       \

    struct {                    \

        t fifo[(itms)];             \

        fifo_count_t items;         \

        fifo_index_t head;          \

        fifo_index_t tail;          \

    } name

/** Create and initialize static FIFO.

 *

 * FIFO is allocated statically.

 * This macro is suitable for creating smaller FIFOs.

 *

 * @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_STATIC(name, t, itms)       \

    FIFO_CREATE_STATIC(name, t, itms) = {       \

        .items = (itms),            \

        .head = 0,              \

        .tail = 0               \

    }

/** Create and prepare dynamic FIFO.

 *

 * FIFO is allocated dynamically.

 * This macro is suitable for creating larger FIFOs.

 *

 * @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_DYNAMIC(name, t, itms)      \

    struct {                    \

        t *fifo;                \

        fifo_count_t items;         \

        fifo_index_t head;          \

        fifo_index_t tail;          \

    } name = {                  \

        .fifo = NULL,               \

        .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 ? (name.head + 1) : 0]

/** 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 ? (name.tail + 1) : 0] = (value) 

/** Allocate memory for dynamic FIFO.

 *

 * @param name FIFO name.

 */

#define fifo_create(name) \

    name.fifo = malloc(sizeof(*name.fifo) * name.items)

#endif