mojo/public/cpp/bindings/array_traits_stl.h

// Copyright 2016 The Chromium Authors
// 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_ARRAY_TRAITS_STL_H_
#define MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_STL_H_

#include <array>
#include <map>
#include <set>
#include <type_traits>
#include <unordered_set>

#include "base/containers/flat_set.h"
#include "base/memory/raw_ptr_exclusion.h"
#include "mojo/public/cpp/bindings/array_traits.h"
#include "mojo/public/cpp/bindings/lib/default_construct_tag_internal.h"

namespace mojo {

template <typename T>
struct ArrayTraits<std::unordered_set<T>> {
  using Element = T;
  using ConstIterator = typename std::unordered_set<T>::const_iterator;

  static bool IsNull(const std::unordered_set<T>& input) {
    // std::unordered_set<> is always converted to non-null mojom array.
    return false;
  }

  static size_t GetSize(const std::unordered_set<T>& input) {
    return input.size();
  }

  static ConstIterator GetBegin(const std::unordered_set<T>& input) {
    return input.begin();
  }

  static void AdvanceIterator(ConstIterator& iterator) { ++iterator; }

  static const T& GetValue(ConstIterator& iterator) { return *iterator; }
};

// This ArrayTraits specialization is used only for serialization.
template <typename T>
struct ArrayTraits<std::set<T>> {
  using Element = T;
  using ConstIterator = typename std::set<T>::const_iterator;

  static bool IsNull(const std::set<T>& input) {
    // std::set<> is always converted to non-null mojom array.
    return false;
  }

  static size_t GetSize(const std::set<T>& input) { return input.size(); }

  static ConstIterator GetBegin(const std::set<T>& input) {
    return input.begin();
  }
  static void AdvanceIterator(ConstIterator& iterator) {
    ++iterator;
  }
  static const T& GetValue(ConstIterator& iterator) {
    return *iterator;
  }
};

// This ArrayTraits specialization is used only for serialization.
template <typename T>
struct ArrayTraits<base::flat_set<T>> {
  using Element = T;
  using ConstIterator = typename base::flat_set<T>::const_iterator;

  static bool IsNull(const base::flat_set<T>& input) {
    // base::flat_set<> is always converted to non-null mojom array.
    return false;
  }
  static size_t GetSize(const base::flat_set<T>& input) { return input.size(); }
  static ConstIterator GetBegin(const base::flat_set<T>& input) {
    return input.begin();
  }
  static void AdvanceIterator(ConstIterator& iterator) { ++iterator; }
  static const T& GetValue(ConstIterator& iterator) { return *iterator; }
};

template <typename K, typename V>
struct MapValuesArrayView {
  explicit MapValuesArrayView(const std::map<K, V>& map) : map(map) {}
  // RAW_PTR_EXCLUSION: Binary size increase.
  RAW_PTR_EXCLUSION const std::map<K, V>& map;
};

// Convenience function to create a MapValuesArrayView<> that infers the
// template arguments from its argument type.
template <typename K, typename V>
MapValuesArrayView<K, V> MapValuesToArray(const std::map<K, V>& map) {
  return MapValuesArrayView<K, V>(map);
}

// This ArrayTraits specialization is used only for serialization and converts
// a map<K, V> into an array<V>, discarding the keys.
template <typename K, typename V>
struct ArrayTraits<MapValuesArrayView<K, V>> {
  using Element = V;
  using ConstIterator = typename std::map<K, V>::const_iterator;

  static bool IsNull(const MapValuesArrayView<K, V>& input) {
    // std::map<> is always converted to non-null mojom array.
    return false;
  }

  static size_t GetSize(const MapValuesArrayView<K, V>& input) {
    return input.map.size();
  }
  static ConstIterator GetBegin(const MapValuesArrayView<K, V>& input) {
    return input.map.begin();
  }
  static void AdvanceIterator(ConstIterator& iterator) { ++iterator; }
  static const V& GetValue(ConstIterator& iterator) { return iterator->second; }
};

// This ArrayTraits specialization is used for conversion between
// std::array<T, N> and array<T, N>.
template <typename T, size_t N>
struct ArrayTraits<std::array<T, N>> {
  using Element = T;

  static bool IsNull(const std::array<T, N>& input) { return false; }

  static size_t GetSize(const std::array<T, N>& input) { return N; }

  static const T& GetAt(const std::array<T, N>& input, size_t index) {
    return input[index];
  }
  static T& GetAt(std::array<T, N>& input, size_t index) {
    return input[index];
  }

  // std::array is fixed size but this is called during deserialization.
  static bool Resize(std::array<T, N>& input, size_t size) {
    if (size != N)
      return false;
    return true;
  }
};

}  // namespace mojo

#endif  // MOJO_PUBLIC_CPP_BINDINGS_ARRAY_TRAITS_STL_H_