00a8377e50PR-URL: https://github.com/nodejs/node/pull/60540 Reviewed-By: Michaël Zasso <targos@protonmail.com> Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
38 lines
1.3 KiB
C
38 lines
1.3 KiB
C
/* Copyright 2025 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Basic common hash functions / constants. */
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#ifndef THIRD_PARTY_BROTLI_ENC_HASH_BASE_H_
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#define THIRD_PARTY_BROTLI_ENC_HASH_BASE_H_
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#include "../common/platform.h"
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/* kHashMul32 multiplier has these properties:
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* The multiplier must be odd. Otherwise we may lose the highest bit.
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* No long streaks of ones or zeros.
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* There is no effort to ensure that it is a prime, the oddity is enough
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for this use.
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* The number has been tuned heuristically against compression benchmarks. */
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static const uint32_t kHashMul32 = 0x1E35A7BD;
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static const uint64_t kHashMul64 =
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BROTLI_MAKE_UINT64_T(0x1FE35A7Bu, 0xD3579BD3u);
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static BROTLI_INLINE uint32_t Hash14(const uint8_t* data) {
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uint32_t h = BROTLI_UNALIGNED_LOAD32LE(data) * kHashMul32;
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/* The higher bits contain more mixture from the multiplication,
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so we take our results from there. */
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return h >> (32 - 14);
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}
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static BROTLI_INLINE uint32_t Hash15(const uint8_t* data) {
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uint32_t h = BROTLI_UNALIGNED_LOAD32LE(data) * kHashMul32;
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/* The higher bits contain more mixture from the multiplication,
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so we take our results from there. */
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return h >> (32 - 15);
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}
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#endif // THIRD_PARTY_BROTLI_ENC_HASH_BASE_H_
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