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996 cejka 1
/*
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 * Copyright (C) 2006 Jakub Jermar
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 * All rights reserved.
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 *
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 * Redistribution and use in source and binary forms, with or without
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 * modification, are permitted provided that the following conditions
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 * are met:
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 *
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 * - Redistributions of source code must retain the above copyright
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 *   notice, this list of conditions and the following disclaimer.
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 * - Redistributions in binary form must reproduce the above copyright
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 *   notice, this list of conditions and the following disclaimer in the
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 *   documentation and/or other materials provided with the distribution.
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 * - The name of the author may not be used to endorse or promote products
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 *   derived from this software without specific prior written permission.
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 *
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 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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 */
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 /** @addtogroup libc
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 * @{
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 */
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/** @file
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 */
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/*
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 * This implementation of FIFO stores values in an array
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 * (static or dynamic). As such, these FIFOs have upper bound
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 * on number of values they can store. Push and pop operations
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 * are done via accessing the array through head and tail indices.
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 * Because of better operation ordering in fifo_pop(), the access
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 * policy for these two indices is to 'increment (mod size of FIFO)
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 * and use'.
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 */
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#ifndef __FIFO_H__
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#define __FIFO_H__
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#include <malloc.h>
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typedef unsigned long fifo_count_t;
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typedef unsigned long fifo_index_t;
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#define FIFO_CREATE_STATIC(name, t, itms)       \
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    struct {                    \
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        t fifo[(itms)];             \
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        fifo_count_t items;         \
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        fifo_index_t head;          \
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        fifo_index_t tail;          \
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    } name
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/** Create and initialize static FIFO.
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 *
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 * FIFO is allocated statically.
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 * This macro is suitable for creating smaller FIFOs.
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 *
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 * @param name Name of FIFO.
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 * @param t Type of values stored in FIFO.
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 * @param itms Number of items that can be stored in FIFO.
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 */
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#define FIFO_INITIALIZE_STATIC(name, t, itms)       \
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    FIFO_CREATE_STATIC(name, t, itms) = {       \
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        .items = (itms),            \
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        .head = 0,              \
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        .tail = 0               \
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    }
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/** Create and prepare dynamic FIFO.
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 *
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 * FIFO is allocated dynamically.
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 * This macro is suitable for creating larger FIFOs.
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 *
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 * @param name Name of FIFO.
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 * @param t Type of values stored in FIFO.
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 * @param itms Number of items that can be stored in FIFO.
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 */
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#define FIFO_INITIALIZE_DYNAMIC(name, t, itms)      \
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    struct {                    \
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        t *fifo;                \
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        fifo_count_t items;         \
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        fifo_index_t head;          \
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        fifo_index_t tail;          \
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    } name = {                  \
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        .fifo = NULL,               \
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        .items = (itms),            \
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        .head = 0,              \
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        .tail = 0               \
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    }
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/** Pop value from head of FIFO.
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 *
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 * @param name FIFO name.
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 *
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 * @return Leading value in FIFO.
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 */
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#define fifo_pop(name) \
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    name.fifo[name.head = (name.head + 1) < name.items ? (name.head + 1) : 0]
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/** Push value to tail of FIFO.
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 *
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 * @param name FIFO name.
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 * @param value Value to be appended to FIFO.
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 *
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 */
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#define fifo_push(name, value) \
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    name.fifo[name.tail = (name.tail + 1) < name.items ? (name.tail + 1) : 0] = (value) 
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/** Allocate memory for dynamic FIFO.
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 *
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 * @param name FIFO name.
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 */
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#define fifo_create(name) \
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    name.fifo = malloc(sizeof(*name.fifo) * name.items)
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#endif
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 /** @}
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 */
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