chromium/base/containers/unique_ptr_adapters.h

// Copyright 2017 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_UNIQUE_PTR_ADAPTERS_H_
#define BASE_CONTAINERS_UNIQUE_PTR_ADAPTERS_H_

#include <memory>

#include "base/memory/raw_ptr.h"

namespace base {

// This transparent comparator allows to lookup by raw pointer in
// a container of unique pointers. This functionality is based on C++14
// extensions to std::set/std::map interface, and can also be used
// with base::flat_set/base::flat_map.
//
// Example usage:
//   Foo* foo = ...
//   std::set<std::unique_ptr<Foo>, base::UniquePtrComparator> set;
//   set.insert(std::unique_ptr<Foo>(foo));
//   ...
//   auto it = set.find(foo);
//   EXPECT_EQ(foo, it->get());
//
// You can find more information about transparent comparisons here:
// http://en.cppreference.com/w/cpp/utility/functional/less_void
struct UniquePtrComparator { … };

// UniquePtrMatcher is useful for finding an element in a container of
// unique_ptrs when you have the raw pointer.
//
// Example usage:
//   std::vector<std::unique_ptr<Foo>> vector;
//   Foo* element = ...
//   auto iter = base::ranges::find_if(vector, MatchesUniquePtr(element));
//
// Example of erasing from container:
//   EraseIf(v, MatchesUniquePtr(element));
//
template <class T, class Deleter = std::default_delete<T>>
struct UniquePtrMatcher {
  explicit UniquePtrMatcher(T* t) : … { … }

  bool operator()(const std::unique_ptr<T, Deleter>& o) { … }

 private:
  const raw_ptr<T, DanglingUntriaged> t_;
};

template <class T, class Deleter = std::default_delete<T>>
UniquePtrMatcher<T, Deleter> MatchesUniquePtr(T* t) { … }

}  // namespace base

#endif  // BASE_CONTAINERS_UNIQUE_PTR_ADAPTERS_H_