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/* lru.c
* LRU cache
* (c) 2002 Karel 'Clock' Kulhavy
* This file is a part of the Links program, released under GPL.
*/
#include "cfg.h"
#ifdef G
#include "links.h"
static inline void row_insert(struct lru_entry **row, struct lru_entry *ptr)
{
ptr->next = *row;
if (ptr->next) ptr->next->previous = &ptr->next;
ptr->previous = row;
*row = ptr;
}
static inline void row_delete(struct lru_entry *ptr)
{
if (ptr->next) ptr->next->previous = ptr->previous;
*ptr->previous = ptr->next;
}
void lru_insert(struct lru *cache, void *entry, struct lru_entry **row, unsigned bytes_consumed)
{
struct lru_entry *new_entry = mem_alloc(sizeof(*new_entry));
new_entry->above = NULL;
new_entry->below = cache->top;
new_entry->data = entry;
new_entry->bytes_consumed = bytes_consumed;
if (new_entry->below)
new_entry->below->above = new_entry;
else
cache->bottom = new_entry;
row_insert(row, new_entry);
cache->top = new_entry;
cache->bytes += bytes_consumed;
cache->items++;
}
/* Returns bottom (or NULL if the cache is empty) but doesn't
* unlink it.
*/
void *lru_get_bottom(struct lru *cache)
{
if (!cache->bottom) return NULL;
return cache->bottom->data;
}
/* Destroys bottom on nonempty cache. If the cache is empty, segmentation
* fault results.
*/
void lru_destroy_bottom(struct lru *cache)
{
struct lru_entry *it = cache->bottom;
cache->bytes -= cache->bottom->bytes_consumed;
cache->items--;
cache->bottom = it->above;
if (cache->bottom)
cache->bottom->below = NULL;
else
cache->top = NULL;
row_delete(it);
mem_free(it);
}
/* Returns a value of "data"
* template is what we search for.
*/
void *lru_lookup(struct lru *cache, void *templat, struct lru_entry **row)
{
struct lru_entry *ptr = *row;
while (ptr) {
if (!cache->compare_function(ptr->data,templat)) {
/* Found */
if (ptr->above) {
if (ptr->below) {
ptr->below->above = ptr->above;
} else {
cache->bottom = ptr->above;
}
ptr->above->below = ptr->below;
ptr->above = NULL;
ptr->below = cache->top;
cache->top->above = ptr;
cache->top = ptr;
}
if (ptr != *row) {
row_delete(ptr);
row_insert(row, ptr);
}
return ptr->data;
}
ptr = ptr->next;
}
return NULL;
}
void lru_init(struct lru *cache, int (*compare_function)(void *entry, void *templat))
{
cache->compare_function = compare_function;
cache->top = NULL;
cache->bottom = NULL;
cache->bytes = 0;
cache->items = 0;
}
#endif
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