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