/* hash.c -- hash table management Copyright (C) 2012 Guus Sliepen This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */ #include "system.h" #include "hash.h" #include "xalloc.h" /* Generic hash function */ static uint32_t hash_function(const void *p, size_t len) { const uint8_t *q = p; uint32_t hash = 0; while(true) { for(int i = len > 4 ? 4 : len; --i;) hash += q[i] << (8 * i); hash *= 0x9e370001UL; // Golden ratio prime. if(len <= 4) break; len -= 4; } return hash; } /* Map 32 bits int onto 0..n-1, without throwing away too many bits if n is 2^8 or 2^16 */ static uint32_t modulo(uint32_t hash, size_t n) { if(n == 0x100) return (hash >> 24) ^ ((hash >> 16) & 0xff) ^ ((hash >> 8) & 0xff) ^ (hash & 0xff); else if(n == 0x10000) return (hash >> 16) ^ (hash & 0xffff); else return hash % n; } /* (De)allocation */ hash_t *hash_alloc(size_t n, size_t size) { hash_t *hash = xzalloc(sizeof *hash); hash->n = n; hash->size = size; hash->keys = xzalloc(hash->n * hash->size); hash->values = xzalloc(hash->n * sizeof *hash->values); return hash; } void hash_free(hash_t *hash) { free(hash->keys); free(hash->values); free(hash); } /* Searching and inserting */ void hash_insert(hash_t *hash, const void *key, const void *value) { uint32_t i = modulo(hash_function(key, hash->size), hash->n); memcpy(hash->keys + i * hash->size, key, hash->size); hash->values[i] = value; } void *hash_search(const hash_t *hash, const void *key) { uint32_t i = modulo(hash_function(key, hash->size), hash->n); if(hash->values[i] && !memcmp(key, hash->keys + i * hash->size, hash->size)) { return (void *)hash->values[i]; } return NULL; } void *hash_search_or_insert(hash_t *hash, const void *key, const void *value) { uint32_t i = modulo(hash_function(key, hash->size), hash->n); if(hash->values[i] && !memcmp(key, hash->keys + i * hash->size, hash->size)) return (void *)hash->values[i]; memcpy(hash->keys + i * hash->size, key, hash->size); hash->values[i] = value; return NULL; } /* Utility functions */ void hash_clear(hash_t *hash) { memset(hash->values, 0, hash->n * sizeof *hash->values); } void hash_resize(hash_t *hash, size_t n) { hash->keys = xrealloc(hash->keys, n * hash->size); hash->values = xrealloc(hash->values, n * sizeof *hash->values); if(n > hash->n) { memset(hash->keys + hash->n * hash->size, 0, (n - hash->n) * hash->size); memset(hash->values + hash->n, 0, (n - hash->n) * sizeof *hash->values); } }