#ifndef LRU_CACHE_H
#define LRU_CACHE_H

#include <stddef.h>

struct lru_cache_entry {
	struct lru_cache_entry *next;
	struct lru_cache_entry *prev;
	struct lru_cache_entry *hash_next;
	unsigned long hash_slot;
};
typedef struct lru_cache_entry lru_entry_t;


/*
	A function which, given an entry, returns a pointer to a buffer
	and a number of bytes to use to generate a hash of the entry.
*/
typedef void (lru_hash_feed_fn)(lru_entry_t *, char **, size_t *);

/*
	A function which compares two entries for equality.
*/
typedef int (lru_entry_cmp_fn)(lru_entry_t *, lru_entry_t *);

struct lru_cache_hashslot_ {
	size_t tally;
	struct lru_cache_entry *entry;
};

struct lru_cache {
	const size_t hash_sz;
	const size_t capacity;

	lru_hash_feed_fn *feed_fn;
	lru_entry_cmp_fn *cmp_fn;

	size_t num_entries;
	struct lru_cache_entry *newest;
	struct lru_cache_entry *oldest;
	struct lru_cache_hashslot_ hash[1];
};

struct lru_cache *lru_cache_new(size_t, size_t, lru_hash_feed_fn *, lru_entry_cmp_fn *);
void lru_cache_insert(struct lru_cache *, lru_entry_t *, lru_entry_t **);
void lru_cache_extract(struct lru_cache *, lru_entry_t *);
lru_entry_t *lru_cache_locate(struct lru_cache *, lru_entry_t *);
void lru_cache_foreach(struct lru_cache *, void (*)(lru_entry_t *, size_t, void *), void *);

#endif /* LRU_CACHE_H */