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      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_LIB_CLONE_EQUALS_UTIL_H_
      6 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_CLONE_EQUALS_UTIL_H_
      7 
      8 #include <type_traits>
      9 #include <unordered_map>
     10 #include <vector>
     11 
     12 #include "base/optional.h"
     13 #include "mojo/public/cpp/bindings/lib/template_util.h"
     14 
     15 namespace mojo {
     16 namespace internal {
     17 
     18 template <typename T>
     19 struct HasCloneMethod {
     20   template <typename U>
     21   static char Test(decltype(&U::Clone));
     22   template <typename U>
     23   static int Test(...);
     24   static const bool value = sizeof(Test<T>(0)) == sizeof(char);
     25 
     26  private:
     27   EnsureTypeIsComplete<T> check_t_;
     28 };
     29 
     30 template <typename T, bool has_clone_method = HasCloneMethod<T>::value>
     31 struct CloneTraits;
     32 
     33 template <typename T>
     34 T Clone(const T& input);
     35 
     36 template <typename T>
     37 struct CloneTraits<T, true> {
     38   static T Clone(const T& input) { return input.Clone(); }
     39 };
     40 
     41 template <typename T>
     42 struct CloneTraits<T, false> {
     43   static T Clone(const T& input) { return input; }
     44 };
     45 
     46 template <typename T>
     47 struct CloneTraits<base::Optional<T>, false> {
     48   static base::Optional<T> Clone(const base::Optional<T>& input) {
     49     if (!input)
     50       return base::nullopt;
     51 
     52     return base::Optional<T>(internal::Clone(*input));
     53   }
     54 };
     55 
     56 template <typename T>
     57 struct CloneTraits<std::vector<T>, false> {
     58   static std::vector<T> Clone(const std::vector<T>& input) {
     59     std::vector<T> result;
     60     result.reserve(input.size());
     61     for (const auto& element : input)
     62       result.push_back(internal::Clone(element));
     63 
     64     return result;
     65   }
     66 };
     67 
     68 template <typename K, typename V>
     69 struct CloneTraits<std::unordered_map<K, V>, false> {
     70   static std::unordered_map<K, V> Clone(const std::unordered_map<K, V>& input) {
     71     std::unordered_map<K, V> result;
     72     for (const auto& element : input) {
     73       result.insert(std::make_pair(internal::Clone(element.first),
     74                                    internal::Clone(element.second)));
     75     }
     76     return result;
     77   }
     78 };
     79 
     80 template <typename T>
     81 T Clone(const T& input) {
     82   return CloneTraits<T>::Clone(input);
     83 };
     84 
     85 template <typename T>
     86 struct HasEqualsMethod {
     87   template <typename U>
     88   static char Test(decltype(&U::Equals));
     89   template <typename U>
     90   static int Test(...);
     91   static const bool value = sizeof(Test<T>(0)) == sizeof(char);
     92 
     93  private:
     94   EnsureTypeIsComplete<T> check_t_;
     95 };
     96 
     97 template <typename T, bool has_equals_method = HasEqualsMethod<T>::value>
     98 struct EqualsTraits;
     99 
    100 template <typename T>
    101 bool Equals(const T& a, const T& b);
    102 
    103 template <typename T>
    104 struct EqualsTraits<T, true> {
    105   static bool Equals(const T& a, const T& b) { return a.Equals(b); }
    106 };
    107 
    108 template <typename T>
    109 struct EqualsTraits<T, false> {
    110   static bool Equals(const T& a, const T& b) { return a == b; }
    111 };
    112 
    113 template <typename T>
    114 struct EqualsTraits<base::Optional<T>, false> {
    115   static bool Equals(const base::Optional<T>& a, const base::Optional<T>& b) {
    116     if (!a && !b)
    117       return true;
    118     if (!a || !b)
    119       return false;
    120 
    121     return internal::Equals(*a, *b);
    122   }
    123 };
    124 
    125 template <typename T>
    126 struct EqualsTraits<std::vector<T>, false> {
    127   static bool Equals(const std::vector<T>& a, const std::vector<T>& b) {
    128     if (a.size() != b.size())
    129       return false;
    130     for (size_t i = 0; i < a.size(); ++i) {
    131       if (!internal::Equals(a[i], b[i]))
    132         return false;
    133     }
    134     return true;
    135   }
    136 };
    137 
    138 template <typename K, typename V>
    139 struct EqualsTraits<std::unordered_map<K, V>, false> {
    140   static bool Equals(const std::unordered_map<K, V>& a,
    141                      const std::unordered_map<K, V>& b) {
    142     if (a.size() != b.size())
    143       return false;
    144     for (const auto& element : a) {
    145       auto iter = b.find(element.first);
    146       if (iter == b.end() || !internal::Equals(element.second, iter->second))
    147         return false;
    148     }
    149     return true;
    150   }
    151 };
    152 
    153 template <typename T>
    154 bool Equals(const T& a, const T& b) {
    155   return EqualsTraits<T>::Equals(a, b);
    156 }
    157 
    158 }  // namespace internal
    159 }  // namespace mojo
    160 
    161 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_CLONE_EQUALS_UTIL_H_
    162