bool,
(sizeof(FunT) <= sizeof(Data::tiny) &&
// Same as is_nothrow_move_constructible, but w/ no template instantiation.
- noexcept(FunT(std::declval<FunT&&>()))
- )>;
+ noexcept(FunT(std::declval<FunT&&>())))>;
using SmallTag = std::true_type;
using HeapTag = std::false_type;
return true;
}
+// Invoke helper
+template <typename F, typename... Args>
+inline auto invoke(F&& f, Args&&... args)
+ -> decltype(std::forward<F>(f)(std::forward<Args>(args)...)) {
+ return std::forward<F>(f)(std::forward<Args>(args)...);
+}
+
+template <typename M, typename C, typename... Args>
+inline auto invoke(M(C::*d), Args&&... args)
+ -> decltype(std::mem_fn(d)(std::forward<Args>(args)...)) {
+ return std::mem_fn(d)(std::forward<Args>(args)...);
+}
+
} // namespace function
} // namespace detail
Function<ReturnType(Args...) const>&& that) noexcept {
return std::move(that);
}
+
+/**
+ * @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>
+class FunctionRef;
+
+template <typename ReturnType, typename... Args>
+class FunctionRef<ReturnType(Args...)> final {
+ using Call = ReturnType (*)(void*, Args&&...);
+
+ void* object_{nullptr};
+ Call call_{&FunctionRef::uninitCall};
+
+ static ReturnType uninitCall(void*, Args&&...) {
+ throw std::bad_function_call();
+ }
+
+ template <typename Fun>
+ static ReturnType call(void* object, Args&&... args) {
+ return static_cast<ReturnType>(detail::function::invoke(
+ *static_cast<Fun*>(object), static_cast<Args&&>(args)...));
+ }
+
+ 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>
+ /* implicit */ FunctionRef(Fun&& fun) noexcept {
+ using ReferencedType = typename std::remove_reference<Fun>::type;
+
+ static_assert(
+ std::is_convertible<
+ typename std::result_of<ReferencedType&(Args && ...)>::type,
+ ReturnType>::value,
+ "FunctionRef cannot be constructed from object with "
+ "incompatible function signature");
+
+ // `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<ReferencedType>;
+ }
+
+ ReturnType operator()(Args... args) const {
+ return call_(object_, static_cast<Args&&>(args)...);
+ }
+};
+
} // namespace folly
--- /dev/null
+/*
+ * Copyright 2016 Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * 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.
+ */
+
+#include <list>
+
+#include <folly/Function.h>
+#include <folly/portability/GTest.h>
+
+using folly::Function;
+using folly::FunctionRef;
+
+TEST(FunctionRef, Simple) {
+ int x = 1000;
+ auto lambda = [&x](int v) { return x += v; };
+
+ FunctionRef<int(int)> fref = lambda;
+ EXPECT_EQ(1005, fref(5));
+ EXPECT_EQ(1011, fref(6));
+ EXPECT_EQ(1018, fref(7));
+
+ FunctionRef<int(int)> const cfref = lambda;
+ EXPECT_EQ(1023, cfref(5));
+ EXPECT_EQ(1029, cfref(6));
+ EXPECT_EQ(1036, cfref(7));
+
+ auto const& clambda = lambda;
+
+ FunctionRef<int(int)> fcref = clambda;
+ EXPECT_EQ(1041, fcref(5));
+ EXPECT_EQ(1047, fcref(6));
+ EXPECT_EQ(1054, fcref(7));
+
+ FunctionRef<int(int)> const cfcref = clambda;
+ EXPECT_EQ(1059, cfcref(5));
+ EXPECT_EQ(1065, cfcref(6));
+ EXPECT_EQ(1072, cfcref(7));
+}
+
+TEST(FunctionRef, FunctionPtr) {
+ int (*funcptr)(int) = [](int v) { return v * v; };
+
+ FunctionRef<int(int)> fref = funcptr;
+ EXPECT_EQ(100, fref(10));
+ EXPECT_EQ(121, fref(11));
+
+ FunctionRef<int(int)> const cfref = funcptr;
+ EXPECT_EQ(100, cfref(10));
+ EXPECT_EQ(121, cfref(11));
+}
+
+TEST(FunctionRef, OverloadedFunctor) {
+ struct OverloadedFunctor {
+ // variant 1
+ int operator()(int x) {
+ return 100 + 1 * x;
+ }
+
+ // variant 2 (const-overload of v1)
+ int operator()(int x) const {
+ return 100 + 2 * x;
+ }
+
+ // variant 3
+ int operator()(int x, int) {
+ return 100 + 3 * x;
+ }
+
+ // variant 4 (const-overload of v3)
+ int operator()(int x, int) const {
+ return 100 + 4 * x;
+ }
+
+ // variant 5 (non-const, has no const-overload)
+ int operator()(int x, char const*) {
+ return 100 + 5 * x;
+ }
+
+ // variant 6 (const only)
+ int operator()(int x, std::vector<int> const&) const {
+ return 100 + 6 * x;
+ }
+ };
+ OverloadedFunctor of;
+ auto const& cof = of;
+
+ FunctionRef<int(int)> variant1 = of;
+ EXPECT_EQ(100 + 1 * 15, variant1(15));
+ FunctionRef<int(int)> const cvariant1 = of;
+ EXPECT_EQ(100 + 1 * 15, cvariant1(15));
+
+ FunctionRef<int(int)> variant2 = cof;
+ EXPECT_EQ(100 + 2 * 16, variant2(16));
+ FunctionRef<int(int)> const cvariant2 = cof;
+ EXPECT_EQ(100 + 2 * 16, cvariant2(16));
+
+ FunctionRef<int(int, int)> variant3 = of;
+ EXPECT_EQ(100 + 3 * 17, variant3(17, 0));
+ FunctionRef<int(int, int)> const cvariant3 = of;
+ EXPECT_EQ(100 + 3 * 17, cvariant3(17, 0));
+
+ FunctionRef<int(int, int)> variant4 = cof;
+ EXPECT_EQ(100 + 4 * 18, variant4(18, 0));
+ FunctionRef<int(int, int)> const cvariant4 = cof;
+ EXPECT_EQ(100 + 4 * 18, cvariant4(18, 0));
+
+ FunctionRef<int(int, char const*)> variant5 = of;
+ EXPECT_EQ(100 + 5 * 19, variant5(19, "foo"));
+ FunctionRef<int(int, char const*)> const cvariant5 = of;
+ EXPECT_EQ(100 + 5 * 19, cvariant5(19, "foo"));
+
+ FunctionRef<int(int, std::vector<int> const&)> variant6 = of;
+ EXPECT_EQ(100 + 6 * 20, variant6(20, {}));
+ EXPECT_EQ(100 + 6 * 20, variant6(20, {1, 2, 3}));
+ FunctionRef<int(int, std::vector<int> const&)> const cvariant6 = of;
+ EXPECT_EQ(100 + 6 * 20, cvariant6(20, {}));
+ EXPECT_EQ(100 + 6 * 20, cvariant6(20, {1, 2, 3}));
+
+ FunctionRef<int(int, std::vector<int> const&)> variant6const = cof;
+ EXPECT_EQ(100 + 6 * 21, variant6const(21, {}));
+ FunctionRef<int(int, std::vector<int> const&)> const cvariant6const = cof;
+ EXPECT_EQ(100 + 6 * 21, cvariant6const(21, {}));
+}
+
+TEST(FunctionRef, DefaultConstructAndAssign) {
+ FunctionRef<int(int, int)> fref;
+
+ EXPECT_THROW(fref(1, 2), std::bad_function_call);
+
+ int (*func)(int, int) = [](int x, int y) { return 10 * x + y; };
+ fref = func;
+
+ EXPECT_EQ(42, fref(4, 2));
+}
+
+template <typename ValueType>
+class ForEach {
+ public:
+ template <typename InputIterator>
+ ForEach(InputIterator begin, InputIterator end)
+ : func_([begin, end](FunctionRef<void(ValueType)> f) {
+ for (auto it = begin; it != end; ++it) {
+ f(*it);
+ }
+ }) {}
+
+ void operator()(FunctionRef<void(ValueType)> f) const {
+ func_(f);
+ }
+
+ private:
+ Function<void(FunctionRef<void(ValueType)>) const> const func_;
+};
+
+TEST(FunctionRef, ForEach) {
+ std::list<int> s{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
+
+ int sum = 0;
+
+ ForEach<int> fe{s.begin(), s.end()};
+
+ fe([&](int x) { sum += x; });
+
+ EXPECT_EQ(55, sum);
+}
projects / folly.git / commitdiff