lru.c

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#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <uthash.h>
 
#include <aaruformat.h>
 
// LRU cache using uthash with native integer keys.
// Based on uthash LRU example by Jehiah Czebotar 2011 (public domain).
// Rewritten to use HASH_FIND/HASH_ADD with uint64_t keys directly,
// eliminating all string conversion, malloc, and snprintf overhead
// from the hot path.

void *find_in_cache_uint64(struct CacheHeader *cache, const uint64_t key)
{
    struct CacheEntry *entry = NULL;
    HASH_FIND(hh, cache->cache, &key, sizeof(uint64_t), entry);
    if(entry)
    {
        // Remove and re-add to move to front of insertion-order list (LRU refresh).
        HASH_DELETE(hh, cache->cache, entry);
        HASH_ADD(hh, cache->cache, key, sizeof(uint64_t), entry);
        return entry->value;
    }
    return NULL;
}

void add_to_cache_uint64(struct CacheHeader *cache, const uint64_t key, void *value)
{
    struct CacheEntry *entry = malloc(sizeof(struct CacheEntry));
    if(!entry) return;
 
    entry->key   = key;
    entry->value = value;
    HASH_ADD(hh, cache->cache, key, sizeof(uint64_t), entry);
 
    // Evict oldest entry if cache exceeded capacity.
    if(HASH_COUNT(cache->cache) > cache->max_items)
    {
        struct CacheEntry *tmp_entry;
        HASH_ITER(hh, cache->cache, entry, tmp_entry)
        {
            HASH_DELETE(hh, cache->cache, entry);
 
            if(cache->free_func && entry->value)
                cache->free_func(entry->value);
 
            free(entry);
            break;
        }
    }
}

void free_cache(struct CacheHeader *cache)
{
    struct CacheEntry *entry, *tmp;
 
    if(!cache || !cache->cache) return;
 
    HASH_ITER(hh, cache->cache, entry, tmp)
    {
        HASH_DELETE(hh, cache->cache, entry);
 
        if(cache->free_func && entry->value)
            cache->free_func(entry->value);
 
        free(entry);
    }
 
    cache->cache = NULL;
}