| // 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: |
| // RAW_PTR_EXCLUSION: References a STACK_ALLOCATED class. 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_ |