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add pjwhash

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Bruno Raoult
2023-06-20 21:27:00 +02:00
parent b803af5ba2
commit 7d98ab73a1
3 changed files with 103 additions and 0 deletions
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53
c/include/pjwhash-inline.h Normal file
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/* pjwhash-inline.h - PJW hash function, inline version.
*
* Copyright (C) 2021-2022 Bruno Raoult ("br")
* Licensed under the GNU General Public License v3.0 or later.
* Some rights reserved. See COPYING.
*
* You should have received a copy of the GNU General Public License along with this
* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
*
* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
*
*/
#ifndef _PJWHASH_INLINE_H
#define _PJWHASH_INLINE_H
#include "bits.h"
#define THREE_QUARTERS ((int) ((BITS_PER_INT * 3) / 4))
#define ONE_EIGHTH ((int) (BITS_PER_INT / 8))
#define HIGH_BITS ( ~((uint)(~0) >> ONE_EIGHTH ))
#ifndef _pjw_inline
#define _pjw_inline static inline
#endif
/**
* unsigned int pjwhash - PJW hash function
* @key: the key address.
* @length: the length of key.
*
* This hash was created by Peter Jay Weinberger (AT&T Bell Labs):
* https://en.wikipedia.org/wiki/PJW_hash_function
*
* Return: the PJW hash.
*/
_pjw_inline uint pjwhash(const void* key, uint length)
{
uint hash = 0, high;
const u8 *k = key;
for (uint i = 0; i < length; ++k, ++i) {
hash = (hash << ONE_EIGHTH) + *k;
high = hash & HIGH_BITS;
if (high != 0) {
hash ^= high >> THREE_QUARTERS;
hash &= ~high;
}
}
return hash;
}
#endif /* _PJWHASH_INLINE_H */

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c/include/pjwhash.h Normal file
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/* pjwhash.h - PJW hash function, extern version.
*
* Copyright (C) 2021-2022 Bruno Raoult ("br")
* Licensed under the GNU General Public License v3.0 or later.
* Some rights reserved. See COPYING.
*
* You should have received a copy of the GNU General Public License along with this
* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
*
* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
*/
#ifndef _PJWHASH_H
#define _PJWHASH_H
#include "bits.h"
/**
* unsigned int pjwhash - PJW hash function
* @key: the key address.
* @length: the length of key.
*
* This hash was created by Peter Jay Weinberger (AT&T Bell Labs):
* https://en.wikipedia.org/wiki/PJW_hash_function
*
* Return: the PJW hash.
*/
extern uint pjwhash (const void* key, uint length);
#endif /* _PJWHASH_H */

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c/pjwhash.c Normal file
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/* pjwhash.c - PJW hash function.
*
* Copyright (C) 2021-2022 Bruno Raoult ("br")
* Licensed under the GNU General Public License v3.0 or later.
* Some rights reserved. See COPYING.
*
* You should have received a copy of the GNU General Public License along with this
* program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
*
* SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
*
*/
#define _pjw_inline extern
//#include "bits.h"
//extern unsigned int pjwhash (const void* key, uint length);
#include "pjwhash.h"
#include "pjwhash-inline.h"