lru.c

/* 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"

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->next=*row;
	new_entry->previous=row;
	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;
	}
	if (new_entry->next){
		new_entry->next->previous=&(new_entry->next);
	}
	*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;
	
	if (it->next){
		it->next->previous=it->previous;
	}
	*(it->previous)=it->next;
	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 *ptr)
{
	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;
			}
			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