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// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef BASE_CONTAINERS_ADAPTERS_H_
#define BASE_CONTAINERS_ADAPTERS_H_
#include <stddef.h>
#include <iterator>
#include <utility>
#include "base/memory/raw_ptr_exclusion.h"
namespace base {
namespace internal {
// Internal adapter class for implementing base::Reversed.
template <typename T>
class ReversedAdapter {
public:
using Iterator = decltype(std::rbegin(std::declval<T&>()));
explicit ReversedAdapter(T& t) : t_(t) {}
ReversedAdapter(const ReversedAdapter& ra) : t_(ra.t_) {}
ReversedAdapter& operator=(const ReversedAdapter&) = delete;
Iterator begin() const { return std::rbegin(t_); }
Iterator end() const { return std::rend(t_); }
private:
// Not a raw_ref<...> for performance reasons: on-stack pointer.
// It is only used inside for loops. Ideally, the container being iterated
// over should be the one held via a raw_ref/raw_ptrs.
RAW_PTR_EXCLUSION T& t_;
};
} // namespace internal
// Reversed returns a container adapter usable in a range-based "for" statement
// for iterating a reversible container in reverse order.
//
// Example:
//
// std::vector<int> v = ...;
// for (int i : base::Reversed(v)) {
// // iterates through v from back to front
// }
template <typename T>
internal::ReversedAdapter<T> Reversed(T& t) {
return internal::ReversedAdapter<T>(t);
}
} // namespace base
#endif // BASE_CONTAINERS_ADAPTERS_H_
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