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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. /** @addtogroup libc
  30.  * @{
  31.  */
  32. /** @file
  33.  */
  34.  
  35. /*
  36.  * This implementation of FIFO stores values in an array
  37.  * (static or dynamic). As such, these FIFOs have upper bound
  38.  * on number of values they can store. Push and pop operations
  39.  * are done via accessing the array through head and tail indices.
  40.  * Because of better operation ordering in fifo_pop(), the access
  41.  * policy for these two indices is to 'increment (mod size of FIFO)
  42.  * and use'.
  43.  */
  44.  
  45. #ifndef LIBC_FIFO_H_
  46. #define LIBC_FIFO_H_
  47.  
  48. #include <malloc.h>
  49.  
  50. typedef unsigned long fifo_count_t;
  51. typedef unsigned long fifo_index_t;
  52.  
  53. #define FIFO_CREATE_STATIC(name, t, itms)       \
  54.     struct {                    \
  55.         t fifo[(itms)];             \
  56.         fifo_count_t items;         \
  57.         fifo_index_t head;          \
  58.         fifo_index_t tail;          \
  59.     } name
  60.  
  61. /** Create and initialize static FIFO.
  62.  *
  63.  * FIFO is allocated statically.
  64.  * This macro is suitable for creating smaller FIFOs.
  65.  *
  66.  * @param name Name of FIFO.
  67.  * @param t Type of values stored in FIFO.
  68.  * @param itms Number of items that can be stored in FIFO.
  69.  */
  70. #define FIFO_INITIALIZE_STATIC(name, t, itms)       \
  71.     FIFO_CREATE_STATIC(name, t, itms) = {       \
  72.         .items = (itms),            \
  73.         .head = 0,              \
  74.         .tail = 0               \
  75.     }
  76.  
  77. /** Create and prepare dynamic FIFO.
  78.  *
  79.  * FIFO is allocated dynamically.
  80.  * This macro is suitable for creating larger FIFOs.
  81.  *
  82.  * @param name Name of FIFO.
  83.  * @param t Type of values stored in FIFO.
  84.  * @param itms Number of items that can be stored in FIFO.
  85.  */
  86. #define FIFO_INITIALIZE_DYNAMIC(name, t, itms)      \
  87.     struct {                    \
  88.         t *fifo;                \
  89.         fifo_count_t items;         \
  90.         fifo_index_t head;          \
  91.         fifo_index_t tail;          \
  92.     } name = {                  \
  93.         .fifo = NULL,               \
  94.         .items = (itms),            \
  95.         .head = 0,              \
  96.         .tail = 0               \
  97.     }
  98.  
  99. /** Pop value from head of FIFO.
  100.  *
  101.  * @param name FIFO name.
  102.  *
  103.  * @return Leading value in FIFO.
  104.  */
  105. #define fifo_pop(name) \
  106.     name.fifo[name.head = (name.head + 1) < name.items ? (name.head + 1) : 0]
  107.  
  108. /** Push value to tail of FIFO.
  109.  *
  110.  * @param name FIFO name.
  111.  * @param value Value to be appended to FIFO.
  112.  *
  113.  */
  114. #define fifo_push(name, value) \
  115.     name.fifo[name.tail = (name.tail + 1) < name.items ? (name.tail + 1) : 0] = (value)
  116.  
  117. /** Allocate memory for dynamic FIFO.
  118.  *
  119.  * @param name FIFO name.
  120.  */
  121. #define fifo_create(name) \
  122.     name.fifo = malloc(sizeof(*name.fifo) * name.items)
  123.  
  124. #endif
  125.  
  126. /** @}
  127.  */
  128.