addon_cache.c

   1 #ifndef ADDON_CACHE_C
   2 #define ADDON_CACHE_C
   3
   4 #include "addon_cache.h"
   5
   6 static addon_cache_node *addon_cache_nodeptr( addon_cache *cache, void *item ){
   7    if( !item ) return NULL;
   8    else return item + cache->offset;
   9 }
  10
  11 static void *addon_cache_item( addon_cache *cache, u16 index ){
  12    if( index == ADDON_CACHE_NIL ) return NULL;
  13    else return cache->buffer + cache->stride*(size_t)index;
  14 }
  15
  16 static void addon_cache_init( addon_cache *cache ){
  17    cache->head = 0;
  18    cache->tail = cache->count -1;
  19    for( i32 ib=0; ib < cache->count; ib++ ){
  20       void *vb = addon_cache_item( cache, ib );
  21       addon_cache_node *nb = addon_cache_nodeptr( cache, vb );
  22
  23       i32 ia = ib-1, ic = ib+1;
  24       nb->l = ia>=0?           ia: ADDON_CACHE_NIL,
  25       nb->r = ic<cache->count? ic: ADDON_CACHE_NIL;
  26       nb->ref_count = 0;
  27    }
  28 }
  29
  30 static u16 addon_item_index( addon_cache *cache, void *item ){
  31    return (item - cache->buffer) / cache->stride;
  32 }
  33
  34 static void *addon_cache_lru( addon_cache *cache ){
  35    u16 head = cache->head;
  36    if( head == ADDON_CACHE_NIL ) return NULL;
  37
  38    void *item = addon_cache_item( cache, head );
  39    addon_cache_node *node = addon_cache_nodeptr( cache, item );
  40
  41    if( cache->head == cache->tail ) cache->tail = ADDON_CACHE_NIL;
  42    cache->head = node->r;
  43
  44    node->l = ADDON_CACHE_NIL;
  45    node->r = ADDON_CACHE_NIL;
  46    return item;
  47 }
  48
  49 static void addon_cache_watch( addon_cache *cache, void *item ){
  50    addon_cache_node *node = addon_cache_nodeptr( cache, item );
  51
  52    if( node->ref_count >= 32 )
  53       vg_fatal_error( "dynamic board watch missmatch (limit is 32)\n" );
  54
  55    node->ref_count ++;
  56 }
  57
  58 /* if after this no more watches, places back into the volatile list */
  59 static void addon_cache_unwatch( addon_cache *cache, void *item ){
  60    addon_cache_node *node = addon_cache_nodeptr( cache, item );
  61
  62    if( node->ref_count == 0 )
  63       vg_fatal_error( "dynamic board unwatch missmatch (no watchers)\n" );
  64
  65    node->ref_count --;
  66    if( !node->ref_count ){
  67       void *item_head = addon_cache_item( cache, cache->head ),
  68            *item_tail = addon_cache_item( cache, cache->tail );
  69       addon_cache_node *head = addon_cache_nodeptr( cache, item_head ),
  70                        *tail = addon_cache_nodeptr( cache, item_tail );
  71
  72       u16 index = addon_item_index( cache, item );
  73       if( tail ) tail->r = index;
  74       node->l = cache->tail;
  75       cache->tail = index;
  76       if( !head ) cache->head = index;
  77    }
  78 }
  79
  80 #endif /* ADDON_CACHE_C */