+++ /dev/null
-/* $Id: tdx-cache.c 5394 2002-04-04 22:55:24Z rra $
-**
-** Cache functions for open overview data files.
-**
-** This code maintains a cache of open overview data files to avoid some of
-** the overhead involved in closing and reopening files. All opens and
-** closes should go through this code, and the hit ratio is tracked to check
-** cache effectiveness.
-*/
-
-#include "config.h"
-#include "clibrary.h"
-#include <time.h>
-
-#include "inn/hashtab.h"
-#include "inn/messages.h"
-#include "libinn.h"
-#include "storage.h"
-#include "tdx-private.h"
-
-/* Returned to callers as an opaque data type, this struct holds all of the
- information about the cache. */
-struct cache {
- struct hash *hashtable;
- unsigned int count;
- unsigned int max;
- unsigned long queries;
- unsigned long hits;
-};
-
-/* A cache entry, holding a group_data struct and some additional information
- used to do cache lookups and to choose what to drop from the cache. */
-struct cache_entry {
- struct group_data *data;
- HASH hash;
- time_t lastused;
-};
-
-
-/*
-** The hash function for a cache_entry. Just return as much of the group
-** hash as can fit in an unsigned long.
-*/
-static unsigned long
-entry_hash(const void *key)
-{
- const HASH *hash = key;
- unsigned long bucket;
-
- memcpy(&bucket, hash, sizeof(bucket));
- return bucket;
-}
-
-
-/*
-** Given a cache_entry, return its key.
-*/
-static const void *
-entry_key(const void *data)
-{
- const struct cache_entry *entry = (const struct cache_entry *) data;
-
- return &entry->hash;
-}
-
-
-/*
-** Check to see if two entries are equal.
-*/
-static bool
-entry_equal(const void *key, const void *data)
-{
- const HASH *hash = (const HASH *) key;
- const struct cache_entry *entry = (const struct cache_entry *) data;
-
- return (memcmp(hash, &entry->hash, sizeof(HASH)) == 0);
-}
-
-
-/*
-** Free a cache entry.
-*/
-static void
-entry_delete(void *data)
-{
- struct cache_entry *entry = (struct cache_entry *) data;
-
- entry->data->refcount--;
- if (entry->data->refcount == 0)
- tdx_data_close(entry->data);
- free(entry);
-}
-
-
-/*
-** Called by hash_traverse, this function finds the oldest entry with the
-** smallest refcount and stores it in the provided pointer so that it can be
-** freed. This is used when the cache is full to drop the least useful
-** entry.
-*/
-static void
-entry_find_oldest(void *data, void *cookie)
-{
- struct cache_entry *entry = (struct cache_entry *) data;
- struct cache_entry **oldest = (struct cache_entry **) cookie;
-
- if (*oldest == NULL) {
- *oldest = entry;
- return;
- }
- if (entry->data->refcount > (*oldest)->data->refcount)
- return;
- if (entry->lastused > (*oldest)->lastused)
- return;
- *oldest = data;
-}
-
-
-/*
-** Create a new cache with the given size.
-*/
-struct cache *
-tdx_cache_create(unsigned int size)
-{
- struct cache *cache;
-
- cache = xmalloc(sizeof(struct cache));
- cache->count = 0;
- cache->max = size;
- cache->queries = 0;
- cache->hits = 0;
- cache->hashtable = hash_create(size * 4 / 3, entry_hash, entry_key,
- entry_equal, entry_delete);
- return cache;
-}
-
-
-/*
-** Look up a particular entry and return it.
-*/
-struct group_data *
-tdx_cache_lookup(struct cache *cache, HASH hash)
-{
- struct cache_entry *entry;
-
- cache->queries++;
- entry = hash_lookup(cache->hashtable, &hash);
- if (entry != NULL) {
- cache->hits++;
- entry->lastused = time(NULL);
- }
- return (entry == NULL) ? NULL : entry->data;
-}
-
-
-/*
-** Insert a new entry, clearing out the oldest entry if the cache is
-** currently full.
-*/
-void
-tdx_cache_insert(struct cache *cache, HASH hash, struct group_data *data)
-{
- struct cache_entry *entry;
-
- if (cache->count == cache->max) {
- struct cache_entry *oldest = NULL;
-
- hash_traverse(cache->hashtable, entry_find_oldest, &oldest);
- if (oldest == NULL) {
- warn("tradindexed: unable to find oldest cache entry");
- return;
- } else {
- if (!hash_delete(cache->hashtable, &oldest->hash)) {
- warn("tradindexed: cannot delete oldest cache entry");
- return;
- }
- }
- cache->count--;
- }
- entry = xmalloc(sizeof(struct cache_entry));
- entry->data = data;
- entry->hash = hash;
- entry->lastused = time(NULL);
- if (!hash_insert(cache->hashtable, &entry->hash, entry)) {
- warn("tradindexed: duplicate cache entry for %s", HashToText(hash));
- free(entry);
- } else {
- entry->data->refcount++;
- cache->count++;
- }
-}
-
-
-/*
-** Delete an entry from the cache.
-*/
-void
-tdx_cache_delete(struct cache *cache, HASH hash)
-{
- if (!hash_delete(cache->hashtable, &hash))
- warn("tradindexed: unable to remove cache entry for %s",
- HashToText(hash));
-}
-
-
-/*
-** Delete the cache and all of the resources that it's holding open.
-*/
-void
-tdx_cache_free(struct cache *cache)
-{
- hash_free(cache->hashtable);
- free(cache);
-}
~ian / innduct.git / blobdiff