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  1. /*
  2.  * Copyright (C) 2006 Jakub Jermar
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /*
  30.  * This implementation of FIFO stores values in an array
  31.  * (static or dynamic). As such, these FIFOs have upper bound
  32.  * on number of values they can store. Push and pop operations
  33.  * are done via accessing the array through head and tail indices.
  34.  * Because of better operation ordering in fifo_pop(), the access
  35.  * policy for these two indices is to 'increment (mod size of FIFO)
  36.  * and use'.
  37.  */
  38.  
  39. #ifndef __FIFO_H__
  40. #define __FIFO_H__
  41.  
  42. #include <malloc.h>
  43.  
  44. typedef unsigned long fifo_count_t;
  45. typedef unsigned long fifo_index_t;
  46.  
  47. #define FIFO_CREATE_STATIC(name, t, itms)       \
  48.     struct {                    \
  49.         t fifo[(itms)];             \
  50.         fifo_count_t items;         \
  51.         fifo_index_t head;          \
  52.         fifo_index_t tail;          \
  53.     } name
  54.  
  55. /** Create and initialize static FIFO.
  56.  *
  57.  * FIFO is allocated statically.
  58.  * This macro is suitable for creating smaller FIFOs.
  59.  *
  60.  * @param name Name of FIFO.
  61.  * @param t Type of values stored in FIFO.
  62.  * @param itms Number of items that can be stored in FIFO.
  63.  */
  64. #define FIFO_INITIALIZE_STATIC(name, t, itms)       \
  65.     FIFO_CREATE_STATIC(name, t, itms) = {       \
  66.         .items = (itms),            \
  67.         .head = 0,              \
  68.         .tail = 0               \
  69.     }
  70.  
  71. /** Create and prepare dynamic FIFO.
  72.  *
  73.  * FIFO is allocated dynamically.
  74.  * This macro is suitable for creating larger FIFOs.
  75.  *
  76.  * @param name Name of FIFO.
  77.  * @param t Type of values stored in FIFO.
  78.  * @param itms Number of items that can be stored in FIFO.
  79.  */
  80. #define FIFO_INITIALIZE_DYNAMIC(name, t, itms)      \
  81.     struct {                    \
  82.         t *fifo;                \
  83.         fifo_count_t items;         \
  84.         fifo_index_t head;          \
  85.         fifo_index_t tail;          \
  86.     } name = {                  \
  87.         .fifo = NULL,               \
  88.         .items = (itms),            \
  89.         .head = 0,              \
  90.         .tail = 0               \
  91.     }
  92.  
  93. /** Pop value from head of FIFO.
  94.  *
  95.  * @param name FIFO name.
  96.  *
  97.  * @return Leading value in FIFO.
  98.  */
  99. #define fifo_pop(name) \
  100.     name.fifo[name.head = (name.head + 1) < name.items ? (name.head + 1) : 0]
  101.  
  102. /** Push value to tail of FIFO.
  103.  *
  104.  * @param name FIFO name.
  105.  * @param value Value to be appended to FIFO.
  106.  *
  107.  */
  108. #define fifo_push(name, value) \
  109.     name.fifo[name.tail = (name.tail + 1) < name.items ? (name.tail + 1) : 0] = (value)
  110.  
  111. /** Allocate memory for dynamic FIFO.
  112.  *
  113.  * @param name FIFO name.
  114.  */
  115. #define fifo_create(name) \
  116.     name.fifo = malloc(sizeof(*name.fifo) * name.items)
  117.  
  118. #endif
  119.