/* -*- 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,

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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 */