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74 lines
1.8 KiB
74 lines
1.8 KiB
4 months ago
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// Copyright 2014 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef BASE_CONTAINERS_ADAPTERS_H_
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#define BASE_CONTAINERS_ADAPTERS_H_
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#include <stddef.h>
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#include <iterator>
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#include "base/macros.h"
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namespace base {
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namespace internal {
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// Internal adapter class for implementing base::Reversed.
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template <typename T>
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class ReversedAdapter {
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public:
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using Iterator = decltype(static_cast<T*>(nullptr)->rbegin());
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explicit ReversedAdapter(T& t) : t_(t) {}
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ReversedAdapter(const ReversedAdapter& ra) : t_(ra.t_) {}
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// TODO(mdempsky): Once we can use C++14 library features, use std::rbegin
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// and std::rend instead, so we can remove the specialization below.
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Iterator begin() const { return t_.rbegin(); }
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Iterator end() const { return t_.rend(); }
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private:
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T& t_;
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DISALLOW_ASSIGN(ReversedAdapter);
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};
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template <typename T, size_t N>
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class ReversedAdapter<T[N]> {
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public:
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using Iterator = std::reverse_iterator<T*>;
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explicit ReversedAdapter(T (&t)[N]) : t_(t) {}
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ReversedAdapter(const ReversedAdapter& ra) : t_(ra.t_) {}
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Iterator begin() const { return Iterator(&t_[N]); }
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Iterator end() const { return Iterator(&t_[0]); }
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private:
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T (&t_)[N];
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DISALLOW_ASSIGN(ReversedAdapter);
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};
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} // namespace internal
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// Reversed returns a container adapter usable in a range-based "for" statement
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// for iterating a reversible container in reverse order.
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//
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// Example:
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//
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// std::vector<int> v = ...;
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// for (int i : base::Reversed(v)) {
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// // iterates through v from back to front
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// }
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template <typename T>
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internal::ReversedAdapter<T> Reversed(T& t) {
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return internal::ReversedAdapter<T>(t);
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}
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} // namespace base
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#endif // BASE_CONTAINERS_ADAPTERS_H_
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