54 lines
1.4 KiB
C
54 lines
1.4 KiB
C
/* pjwhash-inline.h - PJW hash function, inline version.
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*
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* Copyright (C) 2021-2024 Bruno Raoult ("br")
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* Licensed under the GNU General Public License v3.0 or later.
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* Some rights reserved. See COPYING.
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*
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* You should have received a copy of the GNU General Public License along with this
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* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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*
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* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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*
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*/
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#ifndef _PJWHASH_INLINE_H
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#define _PJWHASH_INLINE_H
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#include "brlib.h"
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#define THREE_QUARTERS ((int) ((BITS_PER_INT * 3) / 4))
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#define ONE_EIGHTH ((int) (BITS_PER_INT / 8))
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#define HIGH_BITS ( ~((uint)(~0) >> ONE_EIGHTH ))
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#ifndef _pjw_inline
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#define _pjw_inline static inline
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#endif
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/**
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* unsigned int pjwhash - PJW hash function
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* @key: the key address.
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* @length: the length of key.
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*
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* This hash was created by Peter Jay Weinberger (AT&T Bell Labs):
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* https://en.wikipedia.org/wiki/PJW_hash_function
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*
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* Return: the PJW hash.
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*/
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_pjw_inline uint pjwhash(const void* key, uint length)
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{
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uint hash = 0, high;
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const u8 *k = key;
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for (uint i = 0; i < length; ++k, ++i) {
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hash = (hash << ONE_EIGHTH) + *k;
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high = hash & HIGH_BITS;
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if (high != 0) {
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hash ^= high >> THREE_QUARTERS;
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hash &= ~high;
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}
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}
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return hash;
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}
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#endif /* _PJWHASH_INLINE_H */
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