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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_STL_CONVERTERS_H_
#define MOJO_PUBLIC_CPP_BINDINGS_STL_CONVERTERS_H_
#include <map>
#include <string>
#include <type_traits>
#include <vector>
#include "mojo/public/cpp/bindings/array.h"
#include "mojo/public/cpp/bindings/map.h"
#include "mojo/public/cpp/bindings/string.h"
// Two functions are defined to facilitate conversion between
// mojo::Array/Map/String and std::vector/map/string: mojo::UnwrapToSTLType()
// recursively convert mojo types to STL types; mojo::WrapSTLType() does the
// opposite. For example:
// mojo::Array<mojo::Map<mojo::String, mojo::Array<int32_t>>> mojo_obj;
//
// std::vector<std::map<std::string, std::vector<int32_t>>> stl_obj =
// mojo::UnwrapToSTLType(std::move(mojo_obj));
//
// mojo_obj = mojo::WrapSTLType(std::move(stl_obj));
//
// Notes:
// - The conversion moves as much contents as possible. The two functions both
// take an rvalue ref as input in order to avoid accidental copies.
// - Because std::vector/map/string cannot express null, UnwrapToSTLType()
// converts null mojo::Array/Map/String to empty.
// - The recursive conversion stops at any types that are not the types listed
// above. For example, unwrapping mojo::Array<StructContainingMojoMap> will
// result in std::vector<StructContainingMojoMap>. It won't convert
// mojo::Map inside the struct.
namespace mojo {
namespace internal {
template <typename T>
struct UnwrapTraits;
template <typename T>
struct UnwrapShouldGoDeeper {
public:
static const bool value =
!std::is_same<T, typename UnwrapTraits<T>::Type>::value;
};
template <typename T>
struct UnwrapTraits {
public:
using Type = T;
static Type Unwrap(T input) { return input; }
};
template <typename T>
struct UnwrapTraits<Array<T>> {
public:
using Type = std::vector<typename UnwrapTraits<T>::Type>;
static Type Unwrap(Array<T> input) {
return Helper<T>::Run(std::move(input));
}
private:
template <typename U, bool should_go_deeper = UnwrapShouldGoDeeper<U>::value>
struct Helper {};
template <typename U>
struct Helper<U, true> {
public:
static Type Run(Array<T> input) {
Type output;
output.reserve(input.size());
for (size_t i = 0; i < input.size(); ++i)
output.push_back(UnwrapTraits<T>::Unwrap(std::move(input[i])));
return output;
}
};
template <typename U>
struct Helper<U, false> {
public:
static Type Run(Array<T> input) { return input.PassStorage(); }
};
};
template <typename K, typename V>
struct UnwrapTraits<Map<K, V>> {
public:
using Type =
std::map<typename UnwrapTraits<K>::Type, typename UnwrapTraits<V>::Type>;
static Type Unwrap(Map<K, V> input) {
return Helper<K, V>::Run(std::move(input));
}
private:
template <typename X,
typename Y,
bool should_go_deeper = UnwrapShouldGoDeeper<X>::value ||
UnwrapShouldGoDeeper<Y>::value>
struct Helper {};
template <typename X, typename Y>
struct Helper<X, Y, true> {
public:
static Type Run(Map<K, V> input) {
std::map<K, V> input_storage = input.PassStorage();
Type output;
for (auto& pair : input_storage) {
output.insert(
std::make_pair(UnwrapTraits<K>::Unwrap(pair.first),
UnwrapTraits<V>::Unwrap(std::move(pair.second))));
}
return output;
}
};
template <typename X, typename Y>
struct Helper<X, Y, false> {
public:
static Type Run(Map<K, V> input) { return input.PassStorage(); }
};
};
template <>
struct UnwrapTraits<String> {
public:
using Type = std::string;
static std::string Unwrap(const String& input) { return input; }
};
template <typename T>
struct WrapTraits;
template <typename T>
struct WrapShouldGoDeeper {
public:
static const bool value =
!std::is_same<T, typename WrapTraits<T>::Type>::value;
};
template <typename T>
struct WrapTraits {
public:
using Type = T;
static T Wrap(T input) { return input; }
};
template <typename T>
struct WrapTraits<std::vector<T>> {
public:
using Type = Array<typename WrapTraits<T>::Type>;
static Type Wrap(std::vector<T> input) {
return Helper<T>::Run(std::move(input));
}
private:
template <typename U, bool should_go_deeper = WrapShouldGoDeeper<U>::value>
struct Helper {};
template <typename U>
struct Helper<U, true> {
public:
static Type Run(std::vector<T> input) {
std::vector<typename WrapTraits<T>::Type> output_storage;
output_storage.reserve(input.size());
for (auto& element : input)
output_storage.push_back(WrapTraits<T>::Wrap(std::move(element)));
return Type(std::move(output_storage));
}
};
template <typename U>
struct Helper<U, false> {
public:
static Type Run(std::vector<T> input) { return Type(std::move(input)); }
};
};
template <typename K, typename V>
struct WrapTraits<std::map<K, V>> {
public:
using Type = Map<typename WrapTraits<K>::Type, typename WrapTraits<V>::Type>;
static Type Wrap(std::map<K, V> input) {
return Helper<K, V>::Run(std::move(input));
}
private:
template <typename X,
typename Y,
bool should_go_deeper =
WrapShouldGoDeeper<X>::value || WrapShouldGoDeeper<Y>::value>
struct Helper {};
template <typename X, typename Y>
struct Helper<X, Y, true> {
public:
static Type Run(std::map<K, V> input) {
Type output;
for (auto& pair : input) {
output.insert(WrapTraits<K>::Wrap(pair.first),
WrapTraits<V>::Wrap(std::move(pair.second)));
}
return output;
}
};
template <typename X, typename Y>
struct Helper<X, Y, false> {
public:
static Type Run(std::map<K, V> input) { return Type(std::move(input)); }
};
};
template <>
struct WrapTraits<std::string> {
public:
using Type = String;
static String Wrap(const std::string& input) { return input; }
};
} // namespace internal
template <typename T>
typename internal::UnwrapTraits<T>::Type UnwrapToSTLType(T&& input) {
return internal::UnwrapTraits<T>::Unwrap(std::move(input));
}
template <typename T>
typename internal::WrapTraits<T>::Type WrapSTLType(T&& input) {
return internal::WrapTraits<T>::Wrap(std::move(input));
}
} // namespace mojo
#endif // MOJO_PUBLIC_CPP_BINDINGS_STL_CONVERTERS_H_
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