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