85 lines
2.1 KiB
C++
85 lines
2.1 KiB
C++
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef MOJO_PUBLIC_CPP_BINDINGS_LIB_HASH_UTIL_H_
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#define MOJO_PUBLIC_CPP_BINDINGS_LIB_HASH_UTIL_H_
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#include <cstring>
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#include <functional>
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#include <type_traits>
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#include <vector>
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#include "base/optional.h"
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#include "mojo/public/cpp/bindings/lib/template_util.h"
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namespace mojo {
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namespace internal {
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template <typename T>
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size_t HashCombine(size_t seed, const T& value) {
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// Based on proposal in:
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// http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1756.pdf
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return seed ^ (std::hash<T>()(value) + (seed << 6) + (seed >> 2));
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}
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template <typename T>
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struct HasHashMethod {
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template <typename U>
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static char Test(decltype(&U::Hash));
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template <typename U>
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static int Test(...);
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static const bool value = sizeof(Test<T>(0)) == sizeof(char);
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private:
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EnsureTypeIsComplete<T> check_t_;
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};
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template <typename T, bool has_hash_method = HasHashMethod<T>::value>
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struct HashTraits;
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template <typename T>
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size_t Hash(size_t seed, const T& value);
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template <typename T>
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struct HashTraits<T, true> {
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static size_t Hash(size_t seed, const T& value) { return value.Hash(seed); }
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};
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template <typename T>
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struct HashTraits<T, false> {
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static size_t Hash(size_t seed, const T& value) {
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return HashCombine(seed, value);
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}
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};
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template <typename T>
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struct HashTraits<std::vector<T>, false> {
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static size_t Hash(size_t seed, const std::vector<T>& value) {
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for (const auto& element : value) {
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seed = HashCombine(seed, element);
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}
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return seed;
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}
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};
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template <typename T>
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struct HashTraits<base::Optional<std::vector<T>>, false> {
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static size_t Hash(size_t seed, const base::Optional<std::vector<T>>& value) {
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if (!value)
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return HashCombine(seed, 0);
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return Hash(seed, *value);
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}
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};
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template <typename T>
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size_t Hash(size_t seed, const T& value) {
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return HashTraits<T>::Hash(seed, value);
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}
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} // namespace internal
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} // namespace mojo
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#endif // MOJO_PUBLIC_CPP_BINDINGS_LIB_HASH_UTIL_H_
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