1 // Copyright 2016 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MOJO_PUBLIC_CPP_BINDINGS_EQUALS_TRAITS_H_ 6 #define MOJO_PUBLIC_CPP_BINDINGS_EQUALS_TRAITS_H_ 7 8 #include <type_traits> 9 #include <vector> 10 11 #include "base/containers/flat_map.h" 12 #include "base/optional.h" 13 #include "mojo/public/cpp/bindings/lib/template_util.h" 14 15 namespace mojo { 16 17 // EqualsTraits<> allows you to specify comparison functions for mapped mojo 18 // objects. By default objects can be compared if they implement operator==() 19 // or have a method named Equals(). 20 21 template <typename T> 22 struct HasEqualsMethod { 23 template <typename U> 24 static char Test(decltype(&U::Equals)); 25 template <typename U> 26 static int Test(...); 27 static const bool value = sizeof(Test<T>(0)) == sizeof(char); 28 29 private: 30 internal::EnsureTypeIsComplete<T> check_t_; 31 }; 32 33 template <typename T, bool has_equals_method = HasEqualsMethod<T>::value> 34 struct EqualsTraits; 35 36 template <typename T> 37 bool Equals(const T& a, const T& b); 38 39 template <typename T> 40 struct EqualsTraits<T, true> { 41 static bool Equals(const T& a, const T& b) { return a.Equals(b); } 42 }; 43 44 template <typename T> 45 struct EqualsTraits<T, false> { 46 static bool Equals(const T& a, const T& b) { return a == b; } 47 }; 48 49 template <typename T> 50 struct EqualsTraits<base::Optional<T>, false> { 51 static bool Equals(const base::Optional<T>& a, const base::Optional<T>& b) { 52 if (!a && !b) 53 return true; 54 if (!a || !b) 55 return false; 56 57 // NOTE: Not just Equals() because that's EqualsTraits<>::Equals() and we 58 // want mojo::Equals() for things like base::Optional<std::vector<T>>. 59 return mojo::Equals(*a, *b); 60 } 61 }; 62 63 template <typename T> 64 struct EqualsTraits<std::vector<T>, false> { 65 static bool Equals(const std::vector<T>& a, const std::vector<T>& b) { 66 if (a.size() != b.size()) 67 return false; 68 for (size_t i = 0; i < a.size(); ++i) { 69 if (!mojo::Equals(a[i], b[i])) 70 return false; 71 } 72 return true; 73 } 74 }; 75 76 template <typename K, typename V> 77 struct EqualsTraits<base::flat_map<K, V>, false> { 78 static bool Equals(const base::flat_map<K, V>& a, 79 const base::flat_map<K, V>& b) { 80 if (a.size() != b.size()) 81 return false; 82 for (const auto& element : a) { 83 auto iter = b.find(element.first); 84 if (iter == b.end() || !mojo::Equals(element.second, iter->second)) 85 return false; 86 } 87 return true; 88 } 89 }; 90 91 template <typename T> 92 bool Equals(const T& a, const T& b) { 93 return EqualsTraits<T>::Equals(a, b); 94 } 95 96 } // namespace mojo 97 98 #endif // MOJO_PUBLIC_CPP_BINDINGS_EQUALS_TRAITS_H_ 99