| Avi Drissman | e4622aa | 2022-09-08 20:36:06 | [diff] [blame] | 1 | // Copyright 2014 The Chromium Authors |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 2 | // Use of this source code is governed by a BSD-style license that can be |
| 3 | // found in the LICENSE file. |
| 4 | |
| 5 | #ifndef BASE_CONTAINERS_ADAPTERS_H_ |
| 6 | #define BASE_CONTAINERS_ADAPTERS_H_ |
| 7 | |
| mdempsky | 1379782 | 2015-10-15 01:06:10 | [diff] [blame] | 8 | #include <stddef.h> |
| 9 | |
| 10 | #include <iterator> |
| Avi Drissman | 7ca220e | 2018-12-28 01:53:59 | [diff] [blame] | 11 | #include <utility> |
| mdempsky | 1379782 | 2015-10-15 01:06:10 | [diff] [blame] | 12 | |
| Bartek Nowierski | 0201188 | 2023-06-20 19:00:10 | [diff] [blame] | 13 | #include "base/memory/raw_ptr_exclusion.h" |
| Ali Hijazi | a887789 | 2022-11-10 20:51:03 | [diff] [blame] | 14 | |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 15 | namespace base { |
| 16 | |
| 17 | namespace internal { |
| 18 | |
| 19 | // Internal adapter class for implementing base::Reversed. |
| 20 | template <typename T> |
| 21 | class ReversedAdapter { |
| 22 | public: |
| Avi Drissman | 7ca220e | 2018-12-28 01:53:59 | [diff] [blame] | 23 | using Iterator = decltype(std::rbegin(std::declval<T&>())); |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 24 | |
| 25 | explicit ReversedAdapter(T& t) : t_(t) {} |
| 26 | ReversedAdapter(const ReversedAdapter& ra) : t_(ra.t_) {} |
| Lei Zhang | 6825df4 | 2020-06-23 16:17:43 | [diff] [blame] | 27 | ReversedAdapter& operator=(const ReversedAdapter&) = delete; |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 28 | |
| Bartek Nowierski | 0201188 | 2023-06-20 19:00:10 | [diff] [blame] | 29 | Iterator begin() const { return std::rbegin(t_); } |
| 30 | Iterator end() const { return std::rend(t_); } |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 31 | |
| 32 | private: |
| Bartek Nowierski | f5eeeba | 2024-01-25 12:49:39 | [diff] [blame] | 33 | // RAW_PTR_EXCLUSION: References a STACK_ALLOCATED class. It is only used |
| 34 | // inside for loops. Ideally, the container being iterated over should be the |
| 35 | // one held via a raw_ref/raw_ptrs. |
| Bartek Nowierski | 0201188 | 2023-06-20 19:00:10 | [diff] [blame] | 36 | RAW_PTR_EXCLUSION T& t_; |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 37 | }; |
| 38 | |
| mdempsky | ae84688 | 2014-09-29 18:48:12 | [diff] [blame] | 39 | } // namespace internal |
| 40 | |
| 41 | // Reversed returns a container adapter usable in a range-based "for" statement |
| 42 | // for iterating a reversible container in reverse order. |
| 43 | // |
| 44 | // Example: |
| 45 | // |
| 46 | // std::vector<int> v = ...; |
| 47 | // for (int i : base::Reversed(v)) { |
| 48 | // // iterates through v from back to front |
| 49 | // } |
| 50 | template <typename T> |
| 51 | internal::ReversedAdapter<T> Reversed(T& t) { |
| 52 | return internal::ReversedAdapter<T>(t); |
| 53 | } |
| 54 | |
| 55 | } // namespace base |
| 56 | |
| 57 | #endif // BASE_CONTAINERS_ADAPTERS_H_ |