rckrdmrd
97f407c661
- Prefijo v2: MCH - TRACEABILITY-MASTER.yml creado - Listo para integracion como submodulo Workspace: v2.0.0 | SIMCO: v4.0.0
56 lines
1.4 KiB
C++
56 lines
1.4 KiB
C++
/*
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* Copyright (c) Meta Platforms, Inc. and affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*/
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#pragma once
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#include <cstdint>
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#include <functional>
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#include <string_view>
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#include <react/utils/toLower.h>
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namespace facebook::react {
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/**
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* FNV-1a hash function implementation.
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* Implemented as described in http://www.isthe.com/chongo/tech/comp/fnv/.
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*
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* Please use std::hash if possible. `fnv1a` should only be used in cases
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* when std::hash does not provide the needed functionality. For example,
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* constexpr.
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*/
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template <typename CharTransformT = std::identity>
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constexpr uint32_t fnv1a(std::string_view string) noexcept
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{
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constexpr uint32_t offset_basis = 2166136261;
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uint32_t hash = offset_basis;
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for (const auto &c : string) {
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hash ^= static_cast<int8_t>(CharTransformT{}(c));
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// Using shifts and adds instead of multiplication with a prime number.
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// This is faster when compiled with optimizations.
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hash += (hash << 1) + (hash << 4) + (hash << 7) + (hash << 8) + (hash << 24);
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}
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return hash;
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}
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constexpr uint32_t fnv1aLowercase(std::string_view string)
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{
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struct LowerCaseTransform {
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constexpr char operator()(char c) const
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{
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return toLower(c);
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}
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};
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return fnv1a<LowerCaseTransform>(string);
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}
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} // namespace facebook::react
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