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base / memory / values_equivalent.h [blame]
// Copyright 2022 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_MEMORY_VALUES_EQUIVALENT_H_
#define BASE_MEMORY_VALUES_EQUIVALENT_H_
#include <functional>
#include <memory>
#include <type_traits>
#include "base/memory/scoped_refptr.h"
namespace base {
namespace internal {
template <typename T>
concept IsPointer = std::is_pointer_v<T>;
} // namespace internal
// Compares two pointers for equality, returns the dereferenced value comparison
// if both are non-null.
// Behaves like std::optional<T>::operator==(const std::optional<T>&) but for
// pointers, with an optional predicate.
// If `p` is specified, `p(const T& x, const T& y)` should return whether `x`
// and `y` are equal. It's called with `(*a, *b)` when `a != b && a && b`.
template <typename T, typename Predicate = std::equal_to<>>
bool ValuesEquivalent(const T* a, const T* b, Predicate p = {}) {
if (a == b)
return true;
if (!a || !b)
return false;
return p(*a, *b);
}
// Specialize for smart pointers like std::unique_ptr and base::scoped_refptr
// that provide a T* get() method.
// Example usage:
// struct Example {
// std::unique_ptr<Child> child;
// bool operator==(const Example& other) const {
// return base::ValuesEquivalent(child, other.child);
// }
// };
template <typename T, typename Predicate = std::equal_to<>>
requires requires(const T& t) {
{ t.get() } -> internal::IsPointer;
}
bool ValuesEquivalent(const T& x, const T& y, Predicate p = {}) {
return ValuesEquivalent(x.get(), y.get(), std::move(p));
}
// Specialize for smart pointers like blink::Persistent and blink::Member that
// provide a T* Get() method.
// Example usage:
// namespace blink {
// struct Example : public GarbageCollected<Example> {
// Member<Child> child;
// bool operator==(const Example& other) const {
// return base::ValuesEquivalent(child, other.child);
// }
// void Trace(Visitor*) const;
// };
// } // namespace blink
template <typename T, typename Predicate = std::equal_to<>>
requires requires(const T& t) {
{ t.Get() } -> internal::IsPointer;
}
bool ValuesEquivalent(const T& x, const T& y, Predicate p = {}) {
return ValuesEquivalent(x.Get(), y.Get(), std::move(p));
}
} // namespace base
#endif // BASE_MEMORY_VALUES_EQUIVALENT_H_