31 lines
600 B
C
31 lines
600 B
C
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/*
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* Copyright (C) 2020 Intel Corporation. All rights reserved.
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*
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* SPDX-License-Identifier: BSD-3-Clause
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*/
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#ifndef HASH_H
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#define HASH_H
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#include <types.h>
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/*
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* Hash factor is selected following below formula:
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* - factor64 = 2^64 * ((sqrt(5) - 1)/2)
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* here, ((sqrt(5) - 1)/2) is golden ratio.
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*/
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#define HASH_FACTOR64 0x9E3779B9486E555EUL
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/*
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* Hash function multiplies 64bit key by 64bit hash
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* factor and returns high bits.
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*
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* @pre (bits < 64)
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*/
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static inline uint64_t hash64(uint64_t key, uint32_t bits)
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{
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return (key * HASH_FACTOR64) >> (64U - bits);
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}
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#endif /* HASH_H */
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