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// Copyright 2017 The Chromium Authors. All rights reserved.
// 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>
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 {
using is_transparent = int;
template <typename T, class Deleter = std::default_delete<T>>
bool operator()(const std::unique_ptr<T, Deleter>& lhs,
const std::unique_ptr<T, Deleter>& rhs) const {
return lhs < rhs;
}
template <typename T, class Deleter = std::default_delete<T>>
bool operator()(const T* lhs, const std::unique_ptr<T, Deleter>& rhs) const {
return lhs < rhs.get();
}
template <typename T, class Deleter = std::default_delete<T>>
bool operator()(const std::unique_ptr<T, Deleter>& lhs, const T* rhs) const {
return lhs.get() < rhs;
}
};
// 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 = std::find_if(vector.begin(), vector.end(),
// 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) : t_(t) {}
bool operator()(const std::unique_ptr<T, Deleter>& o) {
return o.get() == t_;
}
private:
T* const t_;
};
template <class T, class Deleter = std::default_delete<T>>
UniquePtrMatcher<T, Deleter> MatchesUniquePtr(T* t) {
return UniquePtrMatcher<T, Deleter>(t);
}
} // namespace base
#endif // BASE_CONTAINERS_UNIQUE_PTR_ADAPTERS_H_
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