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110 lines
3.7 KiB
C
110 lines
3.7 KiB
C
// SPDX-License-Identifier: BSD-2-Clause
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// Copyright (C) 2010 Andrea Mazzoleni
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/** \file
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* Hash functions for the use with ::tommy_hashtable, ::tommy_hashdyn and ::tommy_hashlin.
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*/
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#ifndef __TOMMYHASH_H
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#define __TOMMYHASH_H
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#include "tommytypes.h"
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/******************************************************************************/
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/* hash */
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/**
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* Hash function with a 32 bits result.
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* Implementation of the Robert Jenkins "lookup3" hash 32 bits version,
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* from http://www.burtleburtle.net/bob/hash/doobs.html, function hashlittle().
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*
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* This hash is designed to provide a good overall performance on all platforms,
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* including 32 bits. If you target only 64 bits, you can use faster hashes,
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* like SpookyHash or FarmHash.
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*
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* \param init_val Initialization value.
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* Using a different initialization value, you can generate a completely different set of hash values.
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* Use 0 if not relevant.
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* \param void_key Pointer to the data to hash.
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* \param key_len Size of the data to hash.
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* \note
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* This function is endianness independent.
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* \return The hash value of 32 bits.
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*/
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TOMMY_API tommy_uint32_t tommy_hash_u32(tommy_uint32_t init_val, const void* void_key, tommy_size_t key_len);
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/**
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* Hash function with a 64 bits result.
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* Implementation of the Robert Jenkins "lookup3" hash 64 bits version,
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* from http://www.burtleburtle.net/bob/hash/doobs.html, function hashlittle2().
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*
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* This hash is designed to provide a good overall performance on all platforms,
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* including 32 bits. If you target only 64 bits, you can use faster hashes,
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* like SpookyHash or FarmHash.
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*
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* \param init_val Initialization value.
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* Using a different initialization value, you can generate a completely different set of hash values.
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* Use 0 if not relevant.
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* \param void_key Pointer to the data to hash.
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* \param key_len Size of the data to hash.
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* \note
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* This function is endianness independent.
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* \return The hash value of 64 bits.
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*/
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TOMMY_API tommy_uint64_t tommy_hash_u64(tommy_uint64_t init_val, const void* void_key, tommy_size_t key_len);
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/**
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* String hash function with a 32 bits result.
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* Implementation is based on Robert Jenkins "lookup3" hash 32 bits version,
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* from http://www.burtleburtle.net/bob/hash/doobs.html, function hashlittle().
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*
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* This hash is designed to handle strings with an unknown length. If you
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* know the string length, the other hash functions are surely faster.
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*
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* \param init_val Initialization value.
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* Using a different initialization value, you can generate a completely different set of hash values.
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* Use 0 if not relevant.
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* \param void_key Pointer to the string to hash. It has to be 0 terminated.
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* \note
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* This function is endianness independent.
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* \return The hash value of 32 bits.
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*/
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TOMMY_API tommy_uint32_t tommy_strhash_u32(tommy_uint32_t init_val, const void* void_key);
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/**
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* Integer reversible hash function for 32 bits.
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* Implementation of the Robert Jenkins "4-byte Integer Hashing",
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* from http://burtleburtle.net/bob/hash/integer.html
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*/
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tommy_inline tommy_uint32_t tommy_inthash_u32(tommy_uint32_t key)
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{
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key -= key << 6;
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key ^= key >> 17;
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key -= key << 9;
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key ^= key << 4;
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key -= key << 3;
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key ^= key << 10;
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key ^= key >> 15;
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return key;
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}
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/**
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* Integer reversible hash function for 64 bits.
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* Implementation of the Thomas Wang "Integer Hash Function",
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* from http://web.archive.org/web/20071223173210/http://www.concentric.net/~Ttwang/tech/inthash.htm
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*/
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tommy_inline tommy_uint64_t tommy_inthash_u64(tommy_uint64_t key)
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{
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key = ~key + (key << 21);
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key = key ^ (key >> 24);
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key = key + (key << 3) + (key << 8);
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key = key ^ (key >> 14);
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key = key + (key << 2) + (key << 4);
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key = key ^ (key >> 28);
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key = key + (key << 31);
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return key;
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}
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#endif
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