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