1 /* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */ 2 /* include/k5-hash.h - hash table interface definitions */ 3 /* 4 * Copyright (C) 2018 by the Massachusetts Institute of Technology. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * * Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 14 * * Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in 16 * the documentation and/or other materials provided with the 17 * distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 22 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 23 * COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 24 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES 25 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR 26 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, 28 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 29 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED 30 * OF THE POSSIBILITY OF SUCH DAMAGE. 31 */ 32 33 /* 34 * This file contains declarations for a simple hash table using siphash. Some 35 * limitations which might need to be addressed in the future: 36 * 37 * - The table does not manage caller memory. This limitation could be 38 * addressed by adding an optional free callback to k5_hashtab_create(), to 39 * be called by k5_hashtab_free() and k5_hashtab_remove(). 40 * 41 * - There is no way to iterate over a hash table. 42 * 43 * - k5_hashtab_add() does not check for duplicate entries. 44 */ 45 46 #ifndef K5_HASH_H 47 #define K5_HASH_H 48 49 #define K5_HASH_SEED_LEN 16 50 51 struct k5_hashtab; 52 53 /* 54 * Create a new hash table in *ht_out. seed must point to random bytes if keys 55 * might be under the control of an attacker; otherwise it may be NULL. 56 * initial_buckets controls the initial allocation of hash buckets; pass zero 57 * to use a default value. The number of hash buckets will be doubled as the 58 * number of entries increases. Return 0 on success, ENOMEM on failure. 59 */ 60 int k5_hashtab_create(const uint8_t seed[K5_HASH_SEED_LEN], 61 size_t initial_buckets, struct k5_hashtab **ht_out); 62 63 /* Release the memory used by a hash table. Keys and values are the caller's 64 * responsibility. */ 65 void k5_hashtab_free(struct k5_hashtab *ht); 66 67 /* Add an entry to a hash table. key and val must remain valid until the entry 68 * is removed or the hash table is freed. The caller must avoid duplicates. */ 69 int k5_hashtab_add(struct k5_hashtab *ht, const void *key, size_t klen, 70 void *val); 71 72 /* Remove an entry from a hash table by key. Does not free key or the 73 * associated value. Return 1 if the key was found and removed, 0 if not. */ 74 int k5_hashtab_remove(struct k5_hashtab *ht, const void *key, size_t klen); 75 76 /* Retrieve a value from a hash table by key. */ 77 void *k5_hashtab_get(struct k5_hashtab *ht, const void *key, size_t klen); 78 79 uint64_t k5_siphash24(const uint8_t *data, size_t len, 80 const uint8_t seed[K5_HASH_SEED_LEN]); 81 82 #endif /* K5_HASH_H */ 83