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// 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_EQUALS_TRAITS_H_
#define MOJO_PUBLIC_CPP_BINDINGS_EQUALS_TRAITS_H_
#include <type_traits>
#include <unordered_map>
#include <vector>
#include "base/optional.h"
#include "mojo/public/cpp/bindings/lib/template_util.h"
namespace mojo {
// EqualsTraits<> allows you to specify comparison functions for mapped mojo
// objects. By default objects can be compared if they implement operator==()
// or have a method named Equals().
template <typename T>
struct HasEqualsMethod {
template <typename U>
static char Test(decltype(&U::Equals));
template <typename U>
static int Test(...);
static const bool value = sizeof(Test<T>(0)) == sizeof(char);
private:
internal::EnsureTypeIsComplete<T> check_t_;
};
template <typename T, bool has_equals_method = HasEqualsMethod<T>::value>
struct EqualsTraits;
template <typename T>
bool Equals(const T& a, const T& b);
template <typename T>
struct EqualsTraits<T, true> {
static bool Equals(const T& a, const T& b) { return a.Equals(b); }
};
template <typename T>
struct EqualsTraits<T, false> {
static bool Equals(const T& a, const T& b) { return a == b; }
};
template <typename T>
struct EqualsTraits<base::Optional<T>, false> {
static bool Equals(const base::Optional<T>& a, const base::Optional<T>& b) {
if (!a && !b)
return true;
if (!a || !b)
return false;
// NOTE: Not just Equals() because that's EqualsTraits<>::Equals() and we
// want mojo::Equals() for things like base::Optional<std::vector<T>>.
return mojo::Equals(*a, *b);
}
};
template <typename T>
struct EqualsTraits<std::vector<T>, false> {
static bool Equals(const std::vector<T>& a, const std::vector<T>& b) {
if (a.size() != b.size())
return false;
for (size_t i = 0; i < a.size(); ++i) {
if (!mojo::Equals(a[i], b[i]))
return false;
}
return true;
}
};
template <typename K, typename V>
struct EqualsTraits<std::unordered_map<K, V>, false> {
static bool Equals(const std::unordered_map<K, V>& a,
const std::unordered_map<K, V>& b) {
if (a.size() != b.size())
return false;
for (const auto& element : a) {
auto iter = b.find(element.first);
if (iter == b.end() || !mojo::Equals(element.second, iter->second))
return false;
}
return true;
}
};
template <typename T>
bool Equals(const T& a, const T& b) {
return EqualsTraits<T>::Equals(a, b);
}
} // namespace mojo
#endif // MOJO_PUBLIC_CPP_BINDINGS_EQUALS_TRAITS_H_
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