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// Copyright 2017 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 BASE_VALUE_ITERATORS_H_
#define BASE_VALUE_ITERATORS_H_
#include <memory>
#include <string>
#include <utility>
#include "base/base_export.h"
#include "base/containers/flat_map.h"
namespace base {
class Value;
namespace detail {
using DictStorage = base::flat_map<std::string, std::unique_ptr<Value>>;
// This iterator closely resembles DictStorage::iterator, with one
// important exception. It abstracts the underlying unique_ptr away, meaning its
// value_type is std::pair<const std::string, Value>. It's reference type is a
// std::pair<const std::string&, Value&>, so that callers have read-write
// access without incurring a copy.
class BASE_EXPORT dict_iterator {
public:
using difference_type = DictStorage::iterator::difference_type;
using value_type = std::pair<const std::string, Value>;
using reference = std::pair<const std::string&, Value&>;
using iterator_category = std::bidirectional_iterator_tag;
class pointer {
public:
explicit pointer(const reference& ref);
pointer(const pointer& ptr);
pointer& operator=(const pointer& ptr) = delete;
reference* operator->() { return &ref_; }
private:
reference ref_;
};
explicit dict_iterator(DictStorage::iterator dict_iter);
dict_iterator(const dict_iterator& dict_iter);
dict_iterator& operator=(const dict_iterator& dict_iter);
~dict_iterator();
reference operator*();
pointer operator->();
dict_iterator& operator++();
dict_iterator operator++(int);
dict_iterator& operator--();
dict_iterator operator--(int);
BASE_EXPORT friend bool operator==(const dict_iterator& lhs,
const dict_iterator& rhs);
BASE_EXPORT friend bool operator!=(const dict_iterator& lhs,
const dict_iterator& rhs);
private:
DictStorage::iterator dict_iter_;
};
// This iterator closely resembles DictStorage::const_iterator, with one
// important exception. It abstracts the underlying unique_ptr away, meaning its
// value_type is std::pair<const std::string, Value>. It's reference type is a
// std::pair<const std::string&, const Value&>, so that callers have read-only
// access without incurring a copy.
class BASE_EXPORT const_dict_iterator {
public:
using difference_type = DictStorage::const_iterator::difference_type;
using value_type = std::pair<const std::string, Value>;
using reference = std::pair<const std::string&, const Value&>;
using iterator_category = std::bidirectional_iterator_tag;
class pointer {
public:
explicit pointer(const reference& ref);
pointer(const pointer& ptr);
pointer& operator=(const pointer& ptr) = delete;
const reference* operator->() const { return &ref_; }
private:
const reference ref_;
};
explicit const_dict_iterator(DictStorage::const_iterator dict_iter);
const_dict_iterator(const const_dict_iterator& dict_iter);
const_dict_iterator& operator=(const const_dict_iterator& dict_iter);
~const_dict_iterator();
reference operator*() const;
pointer operator->() const;
const_dict_iterator& operator++();
const_dict_iterator operator++(int);
const_dict_iterator& operator--();
const_dict_iterator operator--(int);
BASE_EXPORT friend bool operator==(const const_dict_iterator& lhs,
const const_dict_iterator& rhs);
BASE_EXPORT friend bool operator!=(const const_dict_iterator& lhs,
const const_dict_iterator& rhs);
private:
DictStorage::const_iterator dict_iter_;
};
// This class wraps the various |begin| and |end| methods of the underlying
// DictStorage in dict_iterators and const_dict_iterators. This allows callers
// to use this class for easy iteration over the underlying values, granting
// them either read-only or read-write access, depending on the
// const-qualification.
class BASE_EXPORT dict_iterator_proxy {
public:
using key_type = DictStorage::key_type;
using mapped_type = DictStorage::mapped_type::element_type;
using value_type = std::pair<key_type, mapped_type>;
using key_compare = DictStorage::key_compare;
using size_type = DictStorage::size_type;
using difference_type = DictStorage::difference_type;
using iterator = dict_iterator;
using const_iterator = const_dict_iterator;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
explicit dict_iterator_proxy(DictStorage* storage);
iterator begin();
const_iterator begin() const;
iterator end();
const_iterator end() const;
reverse_iterator rbegin();
const_reverse_iterator rbegin() const;
reverse_iterator rend();
const_reverse_iterator rend() const;
const_dict_iterator cbegin() const;
const_dict_iterator cend() const;
const_reverse_iterator crbegin() const;
const_reverse_iterator crend() const;
private:
DictStorage* storage_;
};
// This class wraps the various const |begin| and |end| methods of the
// underlying DictStorage in const_dict_iterators. This allows callers to use
// this class for easy iteration over the underlying values, granting them
// either read-only access.
class BASE_EXPORT const_dict_iterator_proxy {
public:
using key_type = const DictStorage::key_type;
using mapped_type = const DictStorage::mapped_type::element_type;
using value_type = std::pair<key_type, mapped_type>;
using key_compare = DictStorage::key_compare;
using size_type = DictStorage::size_type;
using difference_type = DictStorage::difference_type;
using iterator = const_dict_iterator;
using const_iterator = const_dict_iterator;
using reverse_iterator = std::reverse_iterator<iterator>;
using const_reverse_iterator = std::reverse_iterator<const_iterator>;
explicit const_dict_iterator_proxy(const DictStorage* storage);
const_iterator begin() const;
const_iterator end() const;
const_reverse_iterator rbegin() const;
const_reverse_iterator rend() const;
const_iterator cbegin() const;
const_iterator cend() const;
const_reverse_iterator crbegin() const;
const_reverse_iterator crend() const;
private:
const DictStorage* storage_;
};
} // namespace detail
} // namespace base
#endif // BASE_VALUE_ITERATORS_H_
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