tdesktop/Telegram/SourceFiles/base/index_based_iterator.h

136 lines
3.6 KiB
C
Raw Normal View History

/*
This file is part of Telegram Desktop,
the official desktop version of Telegram messaging app, see https://telegram.org
Telegram Desktop is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
It is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
In addition, as a special exception, the copyright holders give permission
to link the code of portions of this program with the OpenSSL library.
Full license: https://github.com/telegramdesktop/tdesktop/blob/master/LICENSE
Copyright (c) 2014-2017 John Preston, https://desktop.telegram.org
*/
#pragma once
#include "base/assertion.h"
namespace base {
template <typename Container>
class index_based_iterator {
public:
using iterator_category = std::random_access_iterator_tag;
using value_type = typename Container::value_type;
using difference_type = typename Container::difference_type;
using pointer = typename Container::pointer;
using reference = typename Container::reference;
index_based_iterator(
Container *container,
typename Container::iterator impl)
: _container(container)
, _index(impl - _container->begin()) {
}
reference operator*() const {
return *(_container->begin() + _index);
}
pointer operator->() const {
return std::addressof(**this);
}
index_based_iterator &operator++() {
++_index;
return *this;
}
index_based_iterator operator++(int) {
auto copy = *this;
++*this;
return copy;
}
index_based_iterator &operator--() {
--_index;
return *this;
}
index_based_iterator operator--(int) {
auto copy = *this;
--*this;
return copy;
}
index_based_iterator &operator+=(difference_type offset) {
_index += offset;
return *this;
}
index_based_iterator operator+(difference_type offset) const {
auto copy = *this;
copy += offset;
return copy;
}
index_based_iterator &operator-=(difference_type offset) {
_index -= offset;
return *this;
}
index_based_iterator operator-(difference_type offset) const {
auto copy = *this;
copy -= offset;
return copy;
}
difference_type operator-(const index_based_iterator &other) const {
return _index - other._index;
}
reference operator[](difference_type offset) const {
return *(*this + offset);
}
bool operator==(const index_based_iterator &other) const {
Expects(_container == other._container);
return _index == other._index;
}
bool operator!=(const index_based_iterator &other) const {
Expects(_container == other._container);
return _index != other._index;
}
bool operator<(const index_based_iterator &other) const {
Expects(_container == other._container);
return _index < other._index;
}
bool operator>(const index_based_iterator &other) const {
return other < *this;
}
bool operator<=(const index_based_iterator &other) const {
return !(other < *this);
}
bool operator>=(const index_based_iterator &other) const {
return !(*this < other);
}
typename Container::iterator base() const {
return _container->begin() + _index;
}
private:
Container *_container = nullptr;
difference_type _index = 0;
};
template <typename Container>
index_based_iterator<Container> index_based_begin(Container &container) {
return { &container, std::begin(container) };
}
template <typename Container>
index_based_iterator<Container> index_based_end(Container &container) {
return { &container, std::end(container) };
}
} // namespace base