/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil -*- */
/* include/k5-hash.h - hash table interface definitions */
/*
* Copyright (C) 2018 by the Massachusetts Institute of Technology.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
* INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
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/*
* This file contains declarations for a simple hash table using siphash. Some
* limitations which might need to be addressed in the future:
*
* - The table does not manage caller memory. This limitation could be
* addressed by adding an optional free callback to k5_hashtab_create(), to
* be called by k5_hashtab_free() and k5_hashtab_remove().
*
* - There is no way to iterate over a hash table.
*
* - k5_hashtab_add() does not check for duplicate entries.
*/
#ifndef K5_HASH_H
#define K5_HASH_H
#define K5_HASH_SEED_LEN 16
struct k5_hashtab;
/*
* Create a new hash table in *ht_out. seed must point to random bytes if keys
* might be under the control of an attacker; otherwise it may be NULL.
* initial_buckets controls the initial allocation of hash buckets; pass zero
* to use a default value. The number of hash buckets will be doubled as the
* number of entries increases. Return 0 on success, ENOMEM on failure.
*/
int k5_hashtab_create(const uint8_t seed[K5_HASH_SEED_LEN],
size_t initial_buckets, struct k5_hashtab **ht_out);
/* Release the memory used by a hash table. Keys and values are the caller's
* responsibility. */
void k5_hashtab_free(struct k5_hashtab *ht);
/* Add an entry to a hash table. key and val must remain valid until the entry
* is removed or the hash table is freed. The caller must avoid duplicates. */
int k5_hashtab_add(struct k5_hashtab *ht, const void *key, size_t klen,
void *val);
/* Remove an entry from a hash table by key. Does not free key or the
* associated value. Return 1 if the key was found and removed, 0 if not. */
int k5_hashtab_remove(struct k5_hashtab *ht, const void *key, size_t klen);
/* Retrieve a value from a hash table by key. */
void *k5_hashtab_get(struct k5_hashtab *ht, const void *key, size_t klen);
uint64_t k5_siphash24(const uint8_t *data, size_t len,
const uint8_t seed[K5_HASH_SEED_LEN]);
#endif /* K5_HASH_H */