caching api

cache.h

#ifndef _CACHE_H_
#define _CACHE_H_

#include "node.h"

struct cache_item {
	void (* release)(struct cache_item *);
	struct node mi;
	struct node li;
};

enum cache_policy {
	CACHE_FIFO,
	CACHE_LIFO,
	CACHE_LRU,
	CACHE_MRU,
	CACHE_LFU,
};

struct cache;
struct cache *cache_create(enum cache_policy p, unsigned int limit);
void cache_destroy(struct cache *c, int release);

struct cache_item *cache_get(struct cache *c, unsigned long key);
int cache_put(struct cache *c, unsigned long key, struct cache_item *ci);
int cache_contains(struct cache *c, unsigned long key);

#endif

example.c

#include <stdio.h>
#include "cache.h"

struct data_item {
	struct cache_item ci;
	char *data;
};

struct data_item *load_data(unsigned int key);
void unload_data(struct data_item *di);
unsigned long map_key(const char *name);

static void data_release(struct cache_item *ci)
{
	struct data_item *di = container_of(ci, struct data_item, ci);

	unload_data(di);
}

static const char *get_data(struct cache *cache, unsigned long key)
{
	struct cache_item *ci;
	struct data_item *di;

	ci = cache_get(cache, key);
	if (ci != NULL) {
		di = container_of(ci, struct data_item, ci);

		return di->data;
	}

	di = load_data(key);
	di->ci.release = data_release;
	cache_put(cache, key, &di->ci);

	return di->data;
}

int main(void)
{
	struct cache *cache;
	char name[256];

	cache = cache_create(CACHE_LFU, 256);

	while (fgets(name, sizeof(name), stdin)) {
		unsigned long key;
		const char *data;

		key = map_key(name);
		if (key == -1)
			continue;

		data = get_data(cache, key);
		printf(stdout, "%s", data);
	}
  
  	cache_destroy(cache, 1);
  	return 0;
}