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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 a statically
  31.  * allocated array created on each FIFO's initialization.
  32.  * As such, these FIFOs have upper bound on number of values
  33.  * they can store. Push and pop operations are done via accessing
  34.  * the array through head and tail indices. Because of better
  35.  * operation ordering in fifo_pop(), the access policy for these
  36.  * two indices is to 'increment (mod size of FIFO) and use'.
  37.  */
  38.  
  39. #ifndef __FIFO_H__
  40. #define __FIFO_H__
  41.  
  42. #include <typedefs.h>
  43.  
  44. /** Create and initialize FIFO.
  45.  *
  46.  * @param name Name of FIFO.
  47.  * @param t Type of values stored in FIFO.
  48.  * @param itms Number of items that can be stored in FIFO.
  49.  */
  50. #define FIFO_INITIALIZE(name, t, itms)          \
  51.     struct {                    \
  52.         t fifo[(itms)];             \
  53.         count_t items;              \
  54.         index_t head;               \
  55.         index_t tail;               \
  56.     } name = {                  \
  57.         .items = (itms),            \
  58.         .head = 0,              \
  59.         .tail = 0               \
  60.     }
  61.  
  62. /** Pop value from head of FIFO.
  63.  *
  64.  * @param name FIFO name.
  65.  *
  66.  * @return Leading value in FIFO.
  67.  */
  68. #define fifo_pop(name) \
  69.     name.fifo[name.head = (name.head + 1) % name.items]
  70.  
  71. /** Push value to tail of FIFO.
  72.  *
  73.  * @param name FIFO name.
  74.  * @param value Value to be appended to FIFO.
  75.  *
  76.  */
  77. #define fifo_push(name, value) \
  78.     name.fifo[name.tail = (name.tail + 1) % name.items] = (value)
  79.  
  80. #endif
  81.