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42 lines
969 B
C++
42 lines
969 B
C++
// Copyright 2016 The RE2 Authors. All Rights Reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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#ifndef UTIL_MIX_H_
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#define UTIL_MIX_H_
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#include <stddef.h>
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#include <limits>
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namespace re2 {
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// Silence "truncation of constant value" warning for kMul in 32-bit mode.
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// Since this is a header file, push and then pop to limit the scope.
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#ifdef _MSC_VER
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#pragma warning(push)
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#pragma warning(disable: 4309)
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#endif
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class HashMix {
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public:
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HashMix() : hash_(1) {}
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explicit HashMix(size_t val) : hash_(val + 83) {}
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void Mix(size_t val) {
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static const size_t kMul = static_cast<size_t>(0xdc3eb94af8ab4c93ULL);
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hash_ *= kMul;
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hash_ = ((hash_ << 19) |
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(hash_ >> (std::numeric_limits<size_t>::digits - 19))) + val;
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}
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size_t get() const { return hash_; }
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private:
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size_t hash_;
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};
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#ifdef _MSC_VER
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#pragma warning(pop)
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#endif
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} // namespace re2
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#endif // UTIL_MIX_H_
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