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72 lines
2.1 KiB
C++
72 lines
2.1 KiB
C++
//------------------------------------------------------------------------------
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/*
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This file is part of Beast: https://github.com/vinniefalco/Beast
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Copyright 2014, Howard Hinnant <howard.hinnant@gmail.com>,
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Vinnie Falco <vinnie.falco@gmail.com
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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 appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL , DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*/
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//==============================================================================
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#ifndef BEAST_HASH_FNV1A_H_INCLUDED
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#define BEAST_HASH_FNV1A_H_INCLUDED
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#include <beast/utility/noexcept.h>
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#include <cstddef>
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#include <cstdint>
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#include <beast/cxx14/type_traits.h> // <type_traits>
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namespace beast {
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// See http://www.isthe.com/chongo/tech/comp/fnv/
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//
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class fnv1a
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{
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private:
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std::uint64_t state_ = 14695981039346656037ULL;
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public:
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using result_type = std::size_t;
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fnv1a() = default;
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template <class Seed,
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std::enable_if_t<
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std::is_unsigned<Seed>::value>* = nullptr>
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explicit
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fnv1a (Seed seed)
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{
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append (&seed, sizeof(seed));
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}
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void
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operator() (void const* key, std::size_t len) noexcept
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{
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unsigned char const* p =
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static_cast<unsigned char const*>(key);
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unsigned char const* const e = p + len;
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for (; p < e; ++p)
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state_ = (state_ ^ *p) * 1099511628211ULL;
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}
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explicit
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operator std::size_t() noexcept
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{
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return static_cast<std::size_t>(state_);
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}
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};
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} // beast
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#endif
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