base/containers/adapters.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   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
   8 #include "base/macros.h"
   9
  10 namespace base {
  11
  12 namespace internal {
  13
  14 // Internal adapter class for implementing base::Reversed.
  15 template <typename T>
  16 class ReversedAdapter {
  17  public:
  18   typedef decltype(static_cast<T*>(nullptr)->rbegin()) Iterator;
  19
  20   explicit ReversedAdapter(T& t) : t_(t) {}
  21   ReversedAdapter(const ReversedAdapter& ra) : t_(ra.t_) {}
  22
  23   Iterator begin() const { return t_.rbegin(); }
  24   Iterator end() const { return t_.rend(); }
  25
  26  private:
  27   T& t_;
  28
  29   DISALLOW_ASSIGN(ReversedAdapter);
  30 };
  31
  32 }  // namespace internal
  33
  34 // Reversed returns a container adapter usable in a range-based "for" statement
  35 // for iterating a reversible container in reverse order.
  36 //
  37 // Example:
  38 //
  39 //   std::vector<int> v = ...;
  40 //   for (int i : base::Reversed(v)) {
  41 //     // iterates through v from back to front
  42 //   }
  43 template <typename T>
  44 internal::ReversedAdapter<T> Reversed(T& t) {
  45   return internal::ReversedAdapter<T>(t);
  46 }
  47
  48 }  // namespace base
  49
  50 #endif  // BASE_CONTAINERS_ADAPTERS_H_