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3dccaa39d8
Currently, we define a CaseInsensitiveStringTraits structure for String. Using this structure for StringView involves allocating a String from that view, and a second string to convert that intermediate string to lowercase. This defines CaseInsensitiveStringViewTraits (and the underlying helper case_insensitive_string_hash) to avoid allocations.
50 lines
1.1 KiB
C++
50 lines
1.1 KiB
C++
/*
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* Copyright (c) 2018-2021, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#pragma once
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#include <AK/Types.h>
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namespace AK {
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constexpr u32 string_hash(char const* characters, size_t length, u32 seed = 0)
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{
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u32 hash = seed;
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for (size_t i = 0; i < length; ++i) {
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hash += (u32)characters[i];
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hash += (hash << 10);
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hash ^= (hash >> 6);
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}
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hash += hash << 3;
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hash ^= hash >> 11;
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hash += hash << 15;
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return hash;
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}
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constexpr u32 case_insensitive_string_hash(char const* characters, size_t length, u32 seed = 0)
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{
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// AK/CharacterTypes.h cannot be included from here.
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auto to_lowercase = [](char ch) -> u32 {
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if (ch >= 'A' && ch <= 'Z')
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return static_cast<u32>(ch) + 0x20;
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return static_cast<u32>(ch);
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};
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u32 hash = seed;
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for (size_t i = 0; i < length; ++i) {
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hash += to_lowercase(characters[i]);
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hash += (hash << 10);
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hash ^= (hash >> 6);
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}
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hash += hash << 3;
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hash ^= hash >> 11;
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hash += hash << 15;
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return hash;
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}
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}
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using AK::string_hash;
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