mirror of
https://github.com/matrix-construct/construct
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52 lines
1.8 KiB
C++
52 lines
1.8 KiB
C++
// Matrix Construct
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//
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// Copyright (C) Matrix Construct Developers, Authors & Contributors
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// Copyright (C) 2016-2018 Jason Volk <jason@zemos.net>
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//
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// Permission to use, copy, modify, and/or distribute this software for any
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// purpose with or without fee is hereby granted, provided that the above
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// copyright notice and this permission notice is present in all copies. The
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// full license for this software is available in the LICENSE file.
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#pragma once
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#define HAVE_IRCD_UTIL_HASH_H
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namespace ircd::util
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{
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// constexpr bernstein string hasher suite; these functions will hash the
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// string at compile time leaving an integer residue at runtime. Decent
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// primes are at least 7681 and 5381.
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template<size_t PRIME = 7681> constexpr size_t hash(const char16_t *const str, const size_t i = 0);
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template<size_t PRIME = 7681> constexpr size_t hash(const string_view str, const size_t i = 0);
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// Note that at runtime this hash uses multiplication on every character
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// which can consume many cycles...
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template<size_t PRIME = 7681> size_t hash(const std::u16string &str, const size_t i = 0);
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}
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/// Runtime hashing of a std::u16string (for js). Non-cryptographic.
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template<size_t PRIME>
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size_t
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ircd::util::hash(const std::u16string &str,
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const size_t i)
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{
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return i >= str.size()? PRIME : (hash(str, i+1) * 33ULL) ^ str.at(i);
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}
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/// Runtime hashing of a string_view. Non-cryptographic.
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template<size_t PRIME>
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constexpr size_t
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ircd::util::hash(const string_view str,
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const size_t i)
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{
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return i >= str.size()? PRIME : (hash(str, i+1) * 33ULL) ^ str.at(i);
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}
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/// Compile-time hashing of a wider string literal (for js). Non-cryptographic.
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template<size_t PRIME>
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constexpr size_t
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ircd::util::hash(const char16_t *const str,
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const size_t i)
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{
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return !str[i]? PRIME : (hash(str, i+1) * 33ULL) ^ str[i];
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}
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