/*
- * Copyright 2016 Facebook, Inc.
- *
- * @author Eric Niebler (eniebler@fb.com), Sven Over (over@fb.com)
+ * Copyright 2017-present Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
- *
+ */
+/*
+ * @author Eric Niebler (eniebler@fb.com), Sven Over (over@fb.com)
* Acknowledgements: Giuseppe Ottaviano (ott@fb.com)
*/
#include <utility>
#include <folly/CppAttributes.h>
+#include <folly/Portability.h>
+#include <folly/Traits.h>
+#include <folly/functional/Invoke.h>
namespace folly {
-namespace impl {
-template <typename FunctionType, bool Const = false>
+template <typename FunctionType>
class Function;
template <typename ReturnType, typename... Args>
-Function<ReturnType(Args...), true> constCastFunction(
- Function<ReturnType(Args...), false>&&) noexcept;
-} // impl
+Function<ReturnType(Args...) const> constCastFunction(
+ Function<ReturnType(Args...)>&&) noexcept;
+
+#if FOLLY_HAVE_NOEXCEPT_FUNCTION_TYPE
+template <typename ReturnType, typename... Args>
+Function<ReturnType(Args...) const noexcept> constCastFunction(
+ Function<ReturnType(Args...) noexcept>&&) noexcept;
+#endif
namespace detail {
namespace function {
union Data {
void* big;
- typename std::aligned_storage<6 * sizeof(void*)>::type small;
+ std::aligned_storage<6 * sizeof(void*)>::type tiny;
};
-template <bool If, typename T>
-using ConstIf = typename std::conditional<If, const T, T>::type;
-
-template <typename Fun, typename FunT = typename std::decay<Fun>::type>
-using IsSmall = std::integral_constant<
- bool,
- (sizeof(FunT) <= sizeof(Data::small) &&
- // Same as is_nothrow_move_constructible, but w/ no template instantiation.
- noexcept(FunT(std::declval<FunT&&>()))
- )>;
+template <typename Fun, typename = Fun*>
+using IsSmall = Conjunction<
+ std::integral_constant<bool, (sizeof(Fun) <= sizeof(Data::tiny))>,
+ std::is_nothrow_move_constructible<Fun>>;
using SmallTag = std::true_type;
using HeapTag = std::false_type;
+template <typename T>
+struct NotFunction : std::true_type {};
+template <typename T>
+struct NotFunction<Function<T>> : std::false_type {};
+
+template <typename T>
+using EnableIfNotFunction =
+ typename std::enable_if<NotFunction<T>::value>::type;
+
+struct CoerceTag {};
+
template <typename T>
bool isNullPtrFn(T* p) {
return p == nullptr;
return {};
}
-template <typename ReturnType, typename... Args>
-ReturnType uninitCall(Data&, Args&&...) {
- throw std::bad_function_call();
-}
inline bool uninitNoop(Op, Data*, Data*) {
return false;
}
+template <typename FunctionType>
+struct FunctionTraits;
+
+template <typename ReturnType, typename... Args>
+struct FunctionTraits<ReturnType(Args...)> {
+ using Call = ReturnType (*)(Data&, Args&&...);
+ using IsConst = std::false_type;
+ using ConstSignature = ReturnType(Args...) const;
+ using NonConstSignature = ReturnType(Args...);
+ using OtherSignature = ConstSignature;
+
+ template <typename F, typename G = typename std::decay<F>::type>
+ using ResultOf = decltype(
+ static_cast<ReturnType>(std::declval<G&>()(std::declval<Args>()...)));
+
+ template <typename Fun>
+ static ReturnType callSmall(Data& p, Args&&... args) {
+ return static_cast<ReturnType>((*static_cast<Fun*>(
+ static_cast<void*>(&p.tiny)))(static_cast<Args&&>(args)...));
+ }
+
+ template <typename Fun>
+ static ReturnType callBig(Data& p, Args&&... args) {
+ return static_cast<ReturnType>(
+ (*static_cast<Fun*>(p.big))(static_cast<Args&&>(args)...));
+ }
+
+ static ReturnType uninitCall(Data&, Args&&...) {
+ throw std::bad_function_call();
+ }
+
+ ReturnType operator()(Args... args) {
+ auto& fn = *static_cast<Function<NonConstSignature>*>(this);
+ return fn.call_(fn.data_, static_cast<Args&&>(args)...);
+ }
+
+ class SharedProxy {
+ std::shared_ptr<Function<NonConstSignature>> sp_;
+
+ public:
+ explicit SharedProxy(Function<NonConstSignature>&& func)
+ : sp_(std::make_shared<Function<NonConstSignature>>(std::move(func))) {}
+ ReturnType operator()(Args&&... args) const {
+ return (*sp_)(static_cast<Args&&>(args)...);
+ }
+ };
+};
+
+template <typename ReturnType, typename... Args>
+struct FunctionTraits<ReturnType(Args...) const> {
+ using Call = ReturnType (*)(Data&, Args&&...);
+ using IsConst = std::true_type;
+ using ConstSignature = ReturnType(Args...) const;
+ using NonConstSignature = ReturnType(Args...);
+ using OtherSignature = NonConstSignature;
+
+ template <typename F, typename G = typename std::decay<F>::type>
+ using ResultOf = decltype(static_cast<ReturnType>(
+ std::declval<const G&>()(std::declval<Args>()...)));
+
+ template <typename Fun>
+ static ReturnType callSmall(Data& p, Args&&... args) {
+ return static_cast<ReturnType>((*static_cast<const Fun*>(
+ static_cast<void*>(&p.tiny)))(static_cast<Args&&>(args)...));
+ }
+
+ template <typename Fun>
+ static ReturnType callBig(Data& p, Args&&... args) {
+ return static_cast<ReturnType>(
+ (*static_cast<const Fun*>(p.big))(static_cast<Args&&>(args)...));
+ }
+
+ static ReturnType uninitCall(Data&, Args&&...) {
+ throw std::bad_function_call();
+ }
+
+ ReturnType operator()(Args... args) const {
+ auto& fn = *static_cast<const Function<ConstSignature>*>(this);
+ return fn.call_(fn.data_, static_cast<Args&&>(args)...);
+ }
+
+ class SharedProxy {
+ std::shared_ptr<Function<ConstSignature>> sp_;
+
+ public:
+ explicit SharedProxy(Function<ConstSignature>&& func)
+ : sp_(std::make_shared<Function<ConstSignature>>(std::move(func))) {}
+ ReturnType operator()(Args&&... args) const {
+ return (*sp_)(static_cast<Args&&>(args)...);
+ }
+ };
+};
+
+#if FOLLY_HAVE_NOEXCEPT_FUNCTION_TYPE
+template <typename ReturnType, typename... Args>
+struct FunctionTraits<ReturnType(Args...) noexcept> {
+ using Call = ReturnType (*)(Data&, Args&&...) noexcept;
+ using IsConst = std::false_type;
+ using ConstSignature = ReturnType(Args...) const noexcept;
+ using NonConstSignature = ReturnType(Args...) noexcept;
+ using OtherSignature = ConstSignature;
+
+ template <typename F, typename G = typename std::decay<F>::type>
+ using ResultOf = decltype(
+ static_cast<ReturnType>(std::declval<G&>()(std::declval<Args>()...)));
+
+ template <typename Fun>
+ static ReturnType callSmall(Data& p, Args&&... args) noexcept {
+ return static_cast<ReturnType>((*static_cast<Fun*>(
+ static_cast<void*>(&p.tiny)))(static_cast<Args&&>(args)...));
+ }
+
+ template <typename Fun>
+ static ReturnType callBig(Data& p, Args&&... args) noexcept {
+ return static_cast<ReturnType>(
+ (*static_cast<Fun*>(p.big))(static_cast<Args&&>(args)...));
+ }
+
+ static ReturnType uninitCall(Data&, Args&&...) noexcept {
+ throw std::bad_function_call();
+ }
+
+ ReturnType operator()(Args... args) noexcept {
+ auto& fn = *static_cast<Function<NonConstSignature>*>(this);
+ return fn.call_(fn.data_, static_cast<Args&&>(args)...);
+ }
+
+ class SharedProxy {
+ std::shared_ptr<Function<NonConstSignature>> sp_;
+
+ public:
+ explicit SharedProxy(Function<NonConstSignature>&& func)
+ : sp_(std::make_shared<Function<NonConstSignature>>(std::move(func))) {}
+ ReturnType operator()(Args&&... args) const {
+ return (*sp_)(static_cast<Args&&>(args)...);
+ }
+ };
+};
+
+template <typename ReturnType, typename... Args>
+struct FunctionTraits<ReturnType(Args...) const noexcept> {
+ using Call = ReturnType (*)(Data&, Args&&...) noexcept;
+ using IsConst = std::true_type;
+ using ConstSignature = ReturnType(Args...) const noexcept;
+ using NonConstSignature = ReturnType(Args...) noexcept;
+ using OtherSignature = NonConstSignature;
+
+ template <typename F, typename G = typename std::decay<F>::type>
+ using ResultOf = decltype(static_cast<ReturnType>(
+ std::declval<const G&>()(std::declval<Args>()...)));
+
+ template <typename Fun>
+ static ReturnType callSmall(Data& p, Args&&... args) noexcept {
+ return static_cast<ReturnType>((*static_cast<const Fun*>(
+ static_cast<void*>(&p.tiny)))(static_cast<Args&&>(args)...));
+ }
+
+ template <typename Fun>
+ static ReturnType callBig(Data& p, Args&&... args) noexcept {
+ return static_cast<ReturnType>(
+ (*static_cast<const Fun*>(p.big))(static_cast<Args&&>(args)...));
+ }
+
+ static ReturnType uninitCall(Data&, Args&&...) noexcept {
+ throw std::bad_function_call();
+ }
+
+ ReturnType operator()(Args... args) const noexcept {
+ auto& fn = *static_cast<const Function<ConstSignature>*>(this);
+ return fn.call_(fn.data_, static_cast<Args&&>(args)...);
+ }
+
+ class SharedProxy {
+ std::shared_ptr<Function<ConstSignature>> sp_;
+
+ public:
+ explicit SharedProxy(Function<ConstSignature>&& func)
+ : sp_(std::make_shared<Function<ConstSignature>>(std::move(func))) {}
+ ReturnType operator()(Args&&... args) const {
+ return (*sp_)(static_cast<Args&&>(args)...);
+ }
+ };
+};
+#endif
+
+template <typename Fun>
+bool execSmall(Op o, Data* src, Data* dst) {
+ switch (o) {
+ case Op::MOVE:
+ ::new (static_cast<void*>(&dst->tiny))
+ Fun(std::move(*static_cast<Fun*>(static_cast<void*>(&src->tiny))));
+ FOLLY_FALLTHROUGH;
+ case Op::NUKE:
+ static_cast<Fun*>(static_cast<void*>(&src->tiny))->~Fun();
+ break;
+ case Op::FULL:
+ return true;
+ case Op::HEAP:
+ break;
+ }
+ return false;
+}
+
+template <typename Fun>
+bool execBig(Op o, Data* src, Data* dst) {
+ switch (o) {
+ case Op::MOVE:
+ dst->big = src->big;
+ src->big = nullptr;
+ break;
+ case Op::NUKE:
+ delete static_cast<Fun*>(src->big);
+ break;
+ case Op::FULL:
+ case Op::HEAP:
+ break;
+ }
+ return true;
+}
+
} // namespace function
} // namespace detail
-namespace impl {
-
-template <typename ReturnType, typename... Args, bool Const>
-class Function<ReturnType(Args...), Const> final {
+template <typename FunctionType>
+class Function final : private detail::function::FunctionTraits<FunctionType> {
// These utility types are defined outside of the template to reduce
// the number of instantiations, and then imported in the class
// namespace for convenience.
using Op = detail::function::Op;
using SmallTag = detail::function::SmallTag;
using HeapTag = detail::function::HeapTag;
- using Call = ReturnType (*)(Data&, Args&&...);
+ using CoerceTag = detail::function::CoerceTag;
+
+ using Traits = detail::function::FunctionTraits<FunctionType>;
+ using Call = typename Traits::Call;
using Exec = bool (*)(Op, Data*, Data*);
- template <typename T>
- using ConstIf = detail::function::ConstIf<Const, T>;
template <typename Fun>
using IsSmall = detail::function::IsSmall<Fun>;
- /**
- * @Function is const-safe:
- * - @call_ takes @Data as non-const param to avoid code/data duplication.
- * - @data_ can only be mutated if @constCastFunction is used.
- */
- mutable Data data_;
- Call call_{&detail::function::uninitCall<ReturnType, Args...>};
+ // The `data_` member is mutable to allow `constCastFunction` to work without
+ // invoking undefined behavior. Const-correctness is only violated when
+ // `FunctionType` is a const function type (e.g., `int() const`) and `*this`
+ // is the result of calling `constCastFunction`.
+ mutable Data data_{};
+ Call call_{&Traits::uninitCall};
Exec exec_{&detail::function::uninitNoop};
- friend Function<ReturnType(Args...), true> constCastFunction<>(
- Function<ReturnType(Args...), false>&&) noexcept;
- friend class Function<ReturnType(Args...), !Const>;
-
- template <typename Fun>
- struct OpsSmall {
- using FunT = typename std::decay<Fun>::type;
- static ReturnType call(Data& p, Args&&... args) {
- return static_cast<ReturnType>((*static_cast<ConstIf<FunT>*>(
- static_cast<void*>(&p.small)))(static_cast<Args&&>(args)...));
- }
- static bool exec(Op o, Data* src, Data* dst) {
- switch (o) {
- case Op::MOVE:
- ::new (static_cast<void*>(&dst->small)) FunT(
- std::move(*static_cast<FunT*>(static_cast<void*>(&src->small))));
- FOLLY_FALLTHROUGH;
- case Op::NUKE:
- static_cast<FunT*>(static_cast<void*>(&src->small))->~FunT();
- break;
- case Op::FULL:
- return true;
- case Op::HEAP:
- break;
- }
- return false;
- }
- };
+ friend Traits;
+ friend Function<typename Traits::ConstSignature> folly::constCastFunction<>(
+ Function<typename Traits::NonConstSignature>&&) noexcept;
+ friend class Function<typename Traits::OtherSignature>;
template <typename Fun>
Function(Fun&& fun, SmallTag) noexcept {
- using Ops = OpsSmall<Fun>;
+ using FunT = typename std::decay<Fun>::type;
if (!detail::function::isNullPtrFn(fun)) {
- ::new (static_cast<void*>(&data_.small))
- typename Ops::FunT(static_cast<Fun&&>(fun));
- exec_ = &Ops::exec;
- call_ = &Ops::call;
+ ::new (static_cast<void*>(&data_.tiny)) FunT(static_cast<Fun&&>(fun));
+ call_ = &Traits::template callSmall<FunT>;
+ exec_ = &detail::function::execSmall<FunT>;
}
}
- template <typename Fun>
- struct OpsHeap {
- using FunT = typename std::decay<Fun>::type;
- static ReturnType call(Data& p, Args&&... args) {
- return static_cast<ReturnType>(
- (*static_cast<ConstIf<FunT>*>(p.big))(static_cast<Args&&>(args)...));
- }
- static bool exec(Op o, Data* src, Data* dst) {
- switch (o) {
- case Op::MOVE:
- dst->big = src->big;
- src->big = nullptr;
- break;
- case Op::NUKE:
- delete static_cast<FunT*>(src->big);
- break;
- case Op::FULL:
- case Op::HEAP:
- break;
- }
- return true;
- }
- };
-
template <typename Fun>
Function(Fun&& fun, HeapTag) {
- using Ops = OpsHeap<Fun>;
- data_.big = new typename Ops::FunT(static_cast<Fun&&>(fun));
- call_ = &Ops::call;
- exec_ = &Ops::exec;
+ using FunT = typename std::decay<Fun>::type;
+ data_.big = new FunT(static_cast<Fun&&>(fun));
+ call_ = &Traits::template callBig<FunT>;
+ exec_ = &detail::function::execBig<FunT>;
}
- template <typename F, typename G = typename std::decay<F>::type>
- using ResultOf = decltype(static_cast<ReturnType>(
- std::declval<ConstIf<G>&>()(std::declval<Args>()...)));
+ template <typename Signature>
+ Function(Function<Signature>&& that, CoerceTag)
+ : Function(static_cast<Function<Signature>&&>(that), HeapTag{}) {}
+
+ Function(
+ Function<typename Traits::OtherSignature>&& that,
+ CoerceTag) noexcept {
+ that.exec_(Op::MOVE, &that.data_, &data_);
+ std::swap(call_, that.call_);
+ std::swap(exec_, that.exec_);
+ }
public:
/**
Function() = default;
// not copyable
- // NOTE: Deleting the non-const copy constructor is unusual but necessary to
- // prevent copies from non-const `Function` object from selecting the
- // perfect forwarding implicit converting constructor below
- // (i.e., `template <typename Fun> Function(Fun&&)`).
- Function(Function&) = delete;
Function(const Function&) = delete;
+#if __OBJC__
+ // Make sure Objective C blocks are copied
+ template <class ReturnType, class... Args>
+ /*implicit*/ Function(ReturnType (^objCBlock)(Args... args))
+ : Function([blockCopy = (ReturnType (^)(Args...))[objCBlock copy]](
+ Args... args) { return blockCopy(args...); }){};
+#endif
+
/**
* Move constructor
*/
/* implicit */ Function(std::nullptr_t) noexcept {}
/**
- * Constructs a new `Function` from any callable object. This
- * handles function pointers, pointers to static member functions,
- * `std::reference_wrapper` objects, `std::function` objects, and arbitrary
- * objects that implement `operator()` if the parameter signature
- * matches (i.e. it returns R when called with Args...).
- * For a `Function` with a const function type, the object must be
- * callable from a const-reference, i.e. implement `operator() const`.
- * For a `Function` with a non-const function type, the object will
- * be called from a non-const reference, which means that it will execute
- * a non-const `operator()` if it is defined, and falls back to
- * `operator() const` otherwise.
+ * Constructs a new `Function` from any callable object that is _not_ a
+ * `folly::Function`. This handles function pointers, pointers to static
+ * member functions, `std::reference_wrapper` objects, `std::function`
+ * objects, and arbitrary objects that implement `operator()` if the parameter
+ * signature matches (i.e. it returns an object convertible to `R` when called
+ * with `Args...`).
*
* \note `typename = ResultOf<Fun>` prevents this overload from being
* selected by overload resolution when `fun` is not a compatible function.
+ *
+ * \note The noexcept requires some explanation. IsSmall is true when the
+ * decayed type fits within the internal buffer and is noexcept-movable. But
+ * this ctor might copy, not move. What we need here, if this ctor does a
+ * copy, is that this ctor be noexcept when the copy is noexcept. That is not
+ * checked in IsSmall, and shouldn't be, because once the Function is
+ * constructed, the contained object is never copied. This check is for this
+ * ctor only, in the case that this ctor does a copy.
*/
- template <class Fun, typename = ResultOf<Fun>>
- /* implicit */ Function(Fun&& fun) noexcept(IsSmall<Fun>::value)
+ template <
+ typename Fun,
+ typename = detail::function::EnableIfNotFunction<Fun>,
+ typename = typename Traits::template ResultOf<Fun>>
+ /* implicit */ Function(Fun fun) noexcept(
+ IsSmall<Fun>::value && noexcept(Fun(std::declval<Fun>())))
: Function(static_cast<Fun&&>(fun), IsSmall<Fun>{}) {}
/**
- * For moving a `Function<X(Ys..) const>` into a `Function<X(Ys...)>`.
+ * For move-constructing from a `folly::Function<X(Ys...) [const?]>`.
+ * For a `Function` with a `const` function type, the object must be
+ * callable from a `const`-reference, i.e. implement `operator() const`.
+ * For a `Function` with a non-`const` function type, the object will
+ * be called from a non-const reference, which means that it will execute
+ * a non-const `operator()` if it is defined, and falls back to
+ * `operator() const` otherwise.
*/
template <
- bool OtherConst,
- typename std::enable_if<!Const && OtherConst, int>::type = 0>
- Function(Function<ReturnType(Args...), OtherConst>&& that) noexcept {
- that.exec_(Op::MOVE, &that.data_, &data_);
- std::swap(call_, that.call_);
- std::swap(exec_, that.exec_);
- }
+ typename Signature,
+ typename = typename Traits::template ResultOf<Function<Signature>>>
+ Function(Function<Signature>&& that) noexcept(
+ noexcept(Function(std::move(that), CoerceTag{})))
+ : Function(std::move(that), CoerceTag{}) {}
/**
* If `ptr` is null, constructs an empty `Function`. Otherwise,
exec_(Op::NUKE, &data_, nullptr);
}
- Function& operator=(Function&) = delete;
Function& operator=(const Function&) = delete;
+#if __OBJC__
+ // Make sure Objective C blocks are copied
+ template <class ReturnType, class... Args>
+ /* implicit */ Function &operator=(ReturnType (^objCBlock)(Args... args)) {
+ (*this) = [blockCopy = (ReturnType (^)(Args...))[objCBlock copy]](
+ Args... args) { return blockCopy(args...); };
+ return *this;
+ }
+#endif
+
/**
* Move assignment operator
+ *
+ * \note Leaves `that` in a valid but unspecified state. If `&that == this`
+ * then `*this` is left in a valid but unspecified state.
*/
Function& operator=(Function&& that) noexcept {
- if (&that != this) {
- // Q: Why is is safe to destroy and reconstruct this object in place?
- // A: Two reasons: First, `Function` is a final class, so in doing this
- // we aren't slicing off any derived parts. And second, the move
- // operation is guaranteed not to throw so we always leave the object
- // in a valid state.
- this->~Function();
- ::new (this) Function(std::move(that));
- }
+ // Q: Why is it safe to destroy and reconstruct this object in place?
+ // A: Two reasons: First, `Function` is a final class, so in doing this
+ // we aren't slicing off any derived parts. And second, the move
+ // operation is guaranteed not to throw so we always leave the object
+ // in a valid state.
+ // In the case of self-move (this == &that), this leaves the object in
+ // a default-constructed state. First the object is destroyed, then we
+ // pass the destroyed object to the move constructor. The first thing the
+ // move constructor does is default-construct the object. That object is
+ // "moved" into itself, which is a no-op for a default-constructed Function.
+ this->~Function();
+ ::new (this) Function(std::move(that));
return *this;
}
* \note `typename = ResultOf<Fun>` prevents this overload from being
* selected by overload resolution when `fun` is not a compatible function.
*/
- template <class Fun, typename = ResultOf<Fun>>
- Function& operator=(Fun&& fun) noexcept(
+ template <typename Fun, typename = decltype(Function(std::declval<Fun>()))>
+ Function& operator=(Fun fun) noexcept(
noexcept(/* implicit */ Function(std::declval<Fun>()))) {
// Doing this in place is more efficient when we can do so safely.
if (noexcept(/* implicit */ Function(std::declval<Fun>()))) {
return *this;
}
+ /**
+ * For assigning from a `Function<X(Ys..) [const?]>`.
+ */
+ template <
+ typename Signature,
+ typename = typename Traits::template ResultOf<Function<Signature>>>
+ Function& operator=(Function<Signature>&& that) noexcept(
+ noexcept(Function(std::move(that)))) {
+ return (*this = Function(std::move(that)));
+ }
+
/**
* Clears this `Function`.
*/
/**
* Call the wrapped callable object with the specified arguments.
- * If this `Function` object is a const `folly::Function` object,
- * this overload shall not participate in overload resolution.
*/
- template <
- // `True` makes `operator()` a template so we can SFINAE on `Const`,
- // which is non-deduced here.
- bool True = true,
- typename std::enable_if<True && !Const, int>::type = 0>
- ReturnType operator()(Args... args) {
- return call_(data_, static_cast<Args&&>(args)...);
- }
-
- /**
- * Call the wrapped callable object with the specified arguments.
- * If this `Function` object is not a const `folly::Function` object,
- * this overload shall not participate in overload resolution.
- */
- template <
- // `True` makes `operator()` a template so we can SFINAE on `Const`,
- // which is non-deduced here.
- bool True = true,
- typename std::enable_if<True && Const, int>::type = 0>
- ReturnType operator()(Args... args) const {
- return call_(data_, static_cast<Args&&>(args)...);
- }
+ using Traits::operator();
/**
* Exchanges the callable objects of `*this` and `that`.
return exec_(Op::HEAP, nullptr, nullptr);
}
+ using typename Traits::SharedProxy;
+
+ /**
+ * Move this `Function` into a copyable callable object, of which all copies
+ * share the state.
+ */
+ SharedProxy asSharedProxy() && {
+ return SharedProxy{std::move(*this)};
+ }
+
/**
* Construct a `std::function` by moving in the contents of this `Function`.
* Note that the returned `std::function` will share its state (i.e. captured
* data) across all copies you make of it, so be very careful when copying.
*/
- std::function<ReturnType(Args...)> asStdFunction() && {
- struct Impl {
- std::shared_ptr<Function> sp_;
- ReturnType operator()(Args&&... args) const {
- return (*sp_)(static_cast<Args&&>(args)...);
- }
- };
- return Impl{std::make_shared<Function>(std::move(*this))};
+ std::function<typename Traits::NonConstSignature> asStdFunction() && {
+ return std::move(*this).asSharedProxy();
}
};
-template <typename FunctionType, bool Const>
-void swap(
- Function<FunctionType, Const>& lhs,
- Function<FunctionType, Const>& rhs) noexcept {
+template <typename FunctionType>
+void swap(Function<FunctionType>& lhs, Function<FunctionType>& rhs) noexcept {
lhs.swap(rhs);
}
-template <typename FunctionType, bool Const>
-bool operator==(const Function<FunctionType, Const>& fn, std::nullptr_t) {
+template <typename FunctionType>
+bool operator==(const Function<FunctionType>& fn, std::nullptr_t) {
return !fn;
}
-template <typename FunctionType, bool Const>
-bool operator==(std::nullptr_t, const Function<FunctionType, Const>& fn) {
+template <typename FunctionType>
+bool operator==(std::nullptr_t, const Function<FunctionType>& fn) {
return !fn;
}
-template <typename FunctionType, bool Const>
-bool operator!=(const Function<FunctionType, Const>& fn, std::nullptr_t) {
+template <typename FunctionType>
+bool operator!=(const Function<FunctionType>& fn, std::nullptr_t) {
return !(fn == nullptr);
}
-template <typename FunctionType, bool Const>
-bool operator!=(std::nullptr_t, const Function<FunctionType, Const>& fn) {
+template <typename FunctionType>
+bool operator!=(std::nullptr_t, const Function<FunctionType>& fn) {
return !(nullptr == fn);
}
/**
- * NOTE: See detailed note about @constCastFunction at the top of the file.
+ * NOTE: See detailed note about `constCastFunction` at the top of the file.
* This is potentially dangerous and requires the equivalent of a `const_cast`.
*/
template <typename ReturnType, typename... Args>
-Function<ReturnType(Args...), true> constCastFunction(
- Function<ReturnType(Args...), false>&& that) noexcept {
- Function<ReturnType(Args...), true> fn{};
- that.exec_(detail::function::Op::MOVE, &that.data_, &fn.data_);
- std::swap(fn.call_, that.call_);
- std::swap(fn.exec_, that.exec_);
- return fn;
+Function<ReturnType(Args...) const> constCastFunction(
+ Function<ReturnType(Args...)>&& that) noexcept {
+ return Function<ReturnType(Args...) const>{std::move(that),
+ detail::function::CoerceTag{}};
}
-template <typename FunctionType>
-Function<FunctionType, true> constCastFunction(
- Function<FunctionType, true>&& that) noexcept {
+template <typename ReturnType, typename... Args>
+Function<ReturnType(Args...) const> constCastFunction(
+ Function<ReturnType(Args...) const>&& that) noexcept {
return std::move(that);
}
-template <typename FunctionType>
-struct MakeFunction {};
-
+#if FOLLY_HAVE_NOEXCEPT_FUNCTION_TYPE
template <typename ReturnType, typename... Args>
-struct MakeFunction<ReturnType(Args...)> {
- using type = Function<ReturnType(Args...), false>;
-};
+Function<ReturnType(Args...) const noexcept> constCastFunction(
+ Function<ReturnType(Args...) noexcept>&& that) noexcept {
+ return Function<ReturnType(Args...) const noexcept>{
+ std::move(that), detail::function::CoerceTag{}};
+}
template <typename ReturnType, typename... Args>
-struct MakeFunction<ReturnType(Args...) const> {
- using type = Function<ReturnType(Args...), true>;
-};
-} // namespace impl
+Function<ReturnType(Args...) const noexcept> constCastFunction(
+ Function<ReturnType(Args...) const noexcept>&& that) noexcept {
+ return std::move(that);
+}
+#endif
-/* using override */ using impl::constCastFunction;
+namespace detail {
+namespace function {
+template <typename Fun, typename FunctionType, typename = void>
+struct IsCallableAsImpl : std::false_type {};
+
+template <typename Fun, typename ReturnType, typename... Args>
+struct IsCallableAsImpl<
+ Fun,
+ ReturnType(Args...),
+ void_t<typename std::result_of<Fun && (Args && ...)>::type>>
+ : std::is_convertible<
+ typename std::result_of<Fun && (Args && ...)>::type,
+ ReturnType> {};
+
+template <typename Fun, typename FunctionType>
+struct IsCallableAs : IsCallableAsImpl<Fun, FunctionType> {};
+} // namespace function
+} // namespace detail
+
+/**
+ * @class FunctionRef
+ *
+ * @brief A reference wrapper for callable objects
+ *
+ * FunctionRef is similar to std::reference_wrapper, but the template parameter
+ * is the function signature type rather than the type of the referenced object.
+ * A folly::FunctionRef is cheap to construct as it contains only a pointer to
+ * the referenced callable and a pointer to a function which invokes the
+ * callable.
+ *
+ * The user of FunctionRef must be aware of the reference semantics: storing a
+ * copy of a FunctionRef is potentially dangerous and should be avoided unless
+ * the referenced object definitely outlives the FunctionRef object. Thus any
+ * function that accepts a FunctionRef parameter should only use it to invoke
+ * the referenced function and not store a copy of it. Knowing that FunctionRef
+ * itself has reference semantics, it is generally okay to use it to reference
+ * lambdas that capture by reference.
+ */
template <typename FunctionType>
-using Function = typename impl::MakeFunction<FunctionType>::type;
-}
+class FunctionRef;
+
+template <typename ReturnType, typename... Args>
+class FunctionRef<ReturnType(Args...)> final {
+ using Call = ReturnType (*)(void*, Args&&...);
+
+ static ReturnType uninitCall(void*, Args&&...) {
+ throw std::bad_function_call();
+ }
+
+ template <typename Fun>
+ static ReturnType call(void* object, Args&&... args) {
+ using Pointer = _t<std::add_pointer<Fun>>;
+ return static_cast<ReturnType>(invoke(
+ static_cast<Fun&&>(*static_cast<Pointer>(object)),
+ static_cast<Args&&>(args)...));
+ }
+
+ void* object_{nullptr};
+ Call call_{&FunctionRef::uninitCall};
+
+ public:
+ /**
+ * Default constructor. Constructs an empty FunctionRef.
+ *
+ * Invoking it will throw std::bad_function_call.
+ */
+ FunctionRef() = default;
+
+ /**
+ * Construct a FunctionRef from a reference to a callable object.
+ */
+ template <
+ typename Fun,
+ typename std::enable_if<
+ Conjunction<
+ Negation<std::is_same<FunctionRef, _t<std::decay<Fun>>>>,
+ detail::function::IsCallableAs<Fun, ReturnType(Args...)>>::value,
+ int>::type = 0>
+ constexpr /* implicit */ FunctionRef(Fun&& fun) noexcept
+ // `Fun` may be a const type, in which case we have to do a const_cast
+ // to store the address in a `void*`. This is safe because the `void*`
+ // will be cast back to `Fun*` (which is a const pointer whenever `Fun`
+ // is a const type) inside `FunctionRef::call`
+ : object_(
+ const_cast<void*>(static_cast<void const*>(std::addressof(fun)))),
+ call_(&FunctionRef::call<Fun>) {}
+
+ ReturnType operator()(Args... args) const {
+ return call_(object_, static_cast<Args&&>(args)...);
+ }
+
+ constexpr explicit operator bool() const {
+ return object_;
+ }
+};
+
+} // namespace folly
projects / folly.git / blobdiff