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/*
* Copyright (c) 2010, Andrea Mazzoleni. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. 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 OWNER 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, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
/** \file
* Hash functions for the use with ::tommy_hashtable, ::tommy_hashdyn and ::tommy_hashlin.
*/
#ifndef __TOMMYHASH_H
#define __TOMMYHASH_H
#include "tommytypes.h"
/******************************************************************************/
/* hash */
/**
* Hash type used in hashtables.
*/
typedef tommy_key_t tommy_hash_t;
/**
* Hash function with a 32 bits result.
* Implementation of the Robert Jenkins "lookup3" hash 32 bits version,
* from http://www.burtleburtle.net/bob/hash/doobs.html, function hashlittle().
*
* This hash is designed to provide a good overall performance in all platforms,
* including 32 bits. If you target only 64 bits, you can use faster hashes,
* like SpookyHash or FarmHash.
*
* \param init_val Initialization value.
* Using a different initialization value, you can generate a completely different set of hash values.
* Use 0 if not relevant.
* \param void_key Pointer to the data to hash.
* \param key_len Size of the data to hash.
* \note
* This function is endianess independent.
* \return The hash value of 32 bits.
*/
tommy_uint32_t tommy_hash_u32(tommy_uint32_t init_val, const void* void_key, tommy_size_t key_len);
/**
* Hash function with a 64 bits result.
* Implementation of the Robert Jenkins "lookup3" hash 64 bits versions,
* from http://www.burtleburtle.net/bob/hash/doobs.html, function hashlittle2().
*
* This hash is designed to provide a good overall performance in all platforms,
* including 32 bits. If you target only 64 bits, you can use faster hashes,
* like SpookyHash or FarmHash.
*
* \param init_val Initialization value.
* Using a different initialization value, you can generate a completely different set of hash values.
* Use 0 if not relevant.
* \param void_key Pointer to the data to hash.
* \param key_len Size of the data to hash.
* \note
* This function is endianess independent.
* \return The hash value of 64 bits.
*/
tommy_uint64_t tommy_hash_u64(tommy_uint64_t init_val, const void* void_key, tommy_size_t key_len);
/**
* String hash function with a 32 bits result.
* Implementation is based on the the Robert Jenkins "lookup3" hash 32 bits version,
* from http://www.burtleburtle.net/bob/hash/doobs.html, function hashlittle().
*
* This hash is designed to handle strings with an unknown length. If you
* know the string length, the other hash functions are surely faster.
*
* \param init_val Initialization value.
* Using a different initialization value, you can generate a completely different set of hash values.
* Use 0 if not relevant.
* \param void_key Pointer to the string to hash. It has to be 0 terminated.
* \note
* This function is endianess independent.
* \return The hash value of 32 bits.
*/
tommy_uint32_t tommy_strhash_u32(tommy_uint64_t init_val, const void* void_key);
/**
* Integer reversible hash function for 32 bits.
* Implementation of the Robert Jenkins "4-byte Integer Hashing",
* from http://burtleburtle.net/bob/hash/integer.html
*/
tommy_inline tommy_uint32_t tommy_inthash_u32(tommy_uint32_t key)
{
key -= key << 6;
key ^= key >> 17;
key -= key << 9;
key ^= key << 4;
key -= key << 3;
key ^= key << 10;
key ^= key >> 15;
return key;
}
/**
* Integer reversible hash function for 64 bits.
* Implementation of the Thomas Wang "Integer Hash Function",
* from http://web.archive.org/web/20071223173210/http://www.concentric.net/~Ttwang/tech/inthash.htm
*/
tommy_inline tommy_uint64_t tommy_inthash_u64(tommy_uint64_t key)
{
key = ~key + (key << 21);
key = key ^ (key >> 24);
key = key + (key << 3) + (key << 8);
key = key ^ (key >> 14);
key = key + (key << 2) + (key << 4);
key = key ^ (key >> 28);
key = key + (key << 31);
return key;
}
#endif
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