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64 lines
1.8 KiB
C++
64 lines
1.8 KiB
C++
// Copyright 2013 The Flutter Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef FLUTTER_FML_MAKE_COPYABLE_H_
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#define FLUTTER_FML_MAKE_COPYABLE_H_
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#include <utility>
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#include "flutter/fml/memory/ref_counted.h"
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#include "flutter/fml/memory/ref_ptr.h"
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namespace fml {
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namespace internal {
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template <typename T>
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class CopyableLambda {
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public:
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explicit CopyableLambda(T func)
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: impl_(MakeRefCounted<Impl>(std::move(func))) {}
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template <typename... ArgType>
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auto operator()(ArgType&&... args) const {
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return impl_->func_(std::forward<ArgType>(args)...);
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}
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private:
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class Impl : public RefCountedThreadSafe<Impl> {
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public:
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explicit Impl(T func) : func_(std::move(func)) {}
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T func_;
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};
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RefPtr<Impl> impl_;
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};
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} // namespace internal
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// Provides a wrapper for a move-only lambda that is implictly convertable to an
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// std::function.
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//
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// std::function is copyable, but if a lambda captures an argument with a
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// move-only type, the lambda itself is not copyable. In order to use the lambda
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// in places that accept std::functions, we provide a copyable object that wraps
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// the lambda and is implicitly convertable to an std::function.
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//
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// EXAMPLE:
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//
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// std::unique_ptr<Foo> foo = ...
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// std::function<int()> func =
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// fml::MakeCopyable([bar = std::move(foo)]() { return bar->count(); });
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//
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// Notice that the return type of MakeCopyable is rarely used directly. Instead,
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// callers typically erase the type by implicitly converting the return value
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// to an std::function.
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template <typename T>
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internal::CopyableLambda<T> MakeCopyable(T lambda) {
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return internal::CopyableLambda<T>(std::move(lambda));
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}
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} // namespace fml
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#endif // FLUTTER_FML_MAKE_COPYABLE_H_
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