firmware/lru.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  *
   9  * Copyright (C) 2003 Tat Tang
  10  *
  11  * This program is free software; you can redistribute it and/or
  12  * modify it under the terms of the GNU General Public License
  13  * as published by the Free Software Foundation; either version 2
  14  * of the License, or (at your option) any later version.
  15  *
  16  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  17  * KIND, either express or implied.
  18  *
  19  ****************************************************************************/
  20
  21 #include "lru.h"
  22
  23 struct lru_node
  24 {
  25     short _next;
  26     short _prev;
  27     unsigned char data[1]; /* place holder */
  28 };
  29
  30 #define lru_node_p(pl, x) \
  31     ((struct lru_node*)(pl->_base + pl->_slot_size * x))
  32
  33 /*******************************************************************************
  34  * lru_create
  35  ******************************************************************************/
  36 void lru_create(struct lru* pl, void *buf, short size, short data_size)
  37 {
  38     pl->_base = (unsigned char*) buf;
  39     pl->_slot_size = data_size + LRU_SLOT_OVERHEAD;
  40
  41     pl->_size = size;
  42
  43     pl->_head = 0;
  44     pl->_tail = pl->_size - 1;
  45
  46     /* Initialise slots */
  47     int i;
  48     for (i=0; i<pl->_size; i++)
  49     {
  50         lru_node_p(pl, i)->_next = i + 1;
  51         lru_node_p(pl, i)->_prev = i - 1;
  52     }
  53
  54     /* Fix up head and tail to form circular buffer */
  55     lru_node_p(pl, 0)->_prev = pl->_tail;
  56     lru_node_p(pl, pl->_tail)->_next = pl->_head;
  57 }
  58
  59 /*******************************************************************************
  60  * lru_traverse
  61  ******************************************************************************/
  62 void lru_traverse(struct lru* pl, void (*callback)(void* data))
  63 {
  64     short i;
  65     struct lru_node* slot;
  66     short loc = pl->_head;
  67
  68     for (i = 0; i < pl->_size; i++)
  69     {
  70         slot = lru_node_p(pl, loc);
  71         callback(slot->data);
  72         loc = slot->_next;
  73     }
  74 }
  75
  76 /*******************************************************************************
  77  * lru_touch
  78  ******************************************************************************/
  79 void lru_touch(struct lru* pl, short handle)
  80 {
  81     if (handle == pl->_head)
  82     {
  83         pl->_head = lru_node_p(pl, pl->_head)->_next;
  84         pl->_tail = lru_node_p(pl, pl->_tail)->_next;
  85         return;
  86     }
  87
  88     if (handle == pl->_tail)
  89     {
  90         return;
  91     }
  92
  93     /* Remove current node from linked list */
  94     struct lru_node* curr_node = lru_node_p(pl, handle);
  95     struct lru_node* prev_node = lru_node_p(pl, curr_node->_prev);
  96     struct lru_node* next_node = lru_node_p(pl, curr_node->_next);
  97
  98     prev_node->_next = curr_node->_next;
  99     next_node->_prev = curr_node->_prev;
 100
 101     /* insert current node at tail */
 102     struct lru_node* tail_node = lru_node_p(pl, pl->_tail);
 103     short tail_node_next_handle = tail_node->_next; /* Bug fix */
 104     struct lru_node* tail_node_next = lru_node_p(pl, tail_node_next_handle); /* Bug fix */
 105
 106     curr_node->_next = tail_node->_next;
 107     curr_node->_prev = pl->_tail;
 108     tail_node_next->_prev = handle; /* Bug fix */
 109     tail_node->_next = handle;
 110
 111     pl->_tail = handle;
 112 }
 113
 114 /*******************************************************************************
 115  * lru_data
 116  ******************************************************************************/
 117 void *lru_data(struct lru* pl, short handle)
 118 {
 119     return lru_node_p(pl, handle)->data;
 120 }
 121