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9a026fc8d5
SipHash is highly HashDoS-resistent, initialized with a random seed at startup (i.e. non-deterministic) and usable for security-critical use cases with large enough parameters. We just use it because it's reasonably secure with parameters 1-3 while having excellent properties and not being significantly slower than before.
56 lines
1.4 KiB
C++
56 lines
1.4 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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// FIXME: This hashing algorithm isn't well-known and may not be good at all.
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// We can't use SipHash since that depends on runtime parameters,
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// but some string hashes like IPC endpoint magic numbers need to be deterministic.
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// Maybe use a SipHash with a statically-known key?
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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 += static_cast<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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#if USING_AK_GLOBALLY
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using AK::string_hash;
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#endif
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