tvl-depot/absl/base/internal/invoke.h

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// Copyright 2017 The Abseil Authors.
//
// 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
//
// https://www.apache.org/licenses/LICENSE-2.0
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//
// 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.
//
// absl::base_internal::Invoke(f, args...) is an implementation of
// INVOKE(f, args...) from section [func.require] of the C++ standard.
//
// [func.require]
// Define INVOKE (f, t1, t2, ..., tN) as follows:
// 1. (t1.*f)(t2, ..., tN) when f is a pointer to a member function of a class T
// and t1 is an object of type T or a reference to an object of type T or a
// reference to an object of a type derived from T;
// 2. ((*t1).*f)(t2, ..., tN) when f is a pointer to a member function of a
// class T and t1 is not one of the types described in the previous item;
// 3. t1.*f when N == 1 and f is a pointer to member data of a class T and t1 is
// an object of type T or a reference to an object of type T or a reference
// to an object of a type derived from T;
// 4. (*t1).*f when N == 1 and f is a pointer to member data of a class T and t1
// is not one of the types described in the previous item;
// 5. f(t1, t2, ..., tN) in all other cases.
//
// The implementation is SFINAE-friendly: substitution failure within Invoke()
// isn't an error.
#ifndef ABSL_BASE_INTERNAL_INVOKE_H_
#define ABSL_BASE_INTERNAL_INVOKE_H_
#include <algorithm>
#include <type_traits>
#include <utility>
Export of internal Abseil changes -- f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e by Andy Soffer <asoffer@google.com>: Ensure that Invoke can support C++17 in the sense that noexcept is part of the type. PiperOrigin-RevId: 261730155 -- bf796ab71653a80498f9374bc8c5111d065c64ba by Abseil Team <absl-team@google.com>: Fix typo in static_assert message for copy/move constructible by replacing "by" with "be". PiperOrigin-RevId: 261713992 -- 8c7c17c40d03a322f304a2fd73ed34462dbf265a by Andy Soffer <asoffer@google.com>: Add absl::is_function drop-in replacement for std::is_function. Some standard libraries incorrectly implement std::is_function in a few corner cases. In particular, libstdc++ functions marked noexcept. The trick being used here is that function types decay to pointers. After excluding cases like is_class, etc, we can distinguish function types by testing for this decay. Many thanks to ericwf@ for essentially writing this CL. PiperOrigin-RevId: 261705008 -- c5adf42d0a132c2525d17a719329eab2ffe0aa94 by Abseil Team <absl-team@google.com>: Add microbenchmark for StrSplit that uses delimiter ByAnyChar. PiperOrigin-RevId: 261424010 -- 66a342f9381ec56be2fe3aa5b3193dd3538a9740 by Andy Soffer <asoffer@google.com>: CMake support for Abseil Random This change touches almost build-related files for CMake almost exclusively. The one minor exception is random/internal/salted_seed_seq.h. The default warnings configuration for one of our CI builds requests not having named but unused parameters. The change in this file cleans up that warning. PiperOrigin-RevId: 261192369 GitOrigin-RevId: f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e Change-Id: I05f662baacfe78750651535aa658f61c2327bc44
2019-08-05 20:32:04 +02:00
#include "absl/meta/type_traits.h"
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// The following code is internal implementation detail. See the comment at the
// top of this file for the API documentation.
namespace absl {
namespace base_internal {
// The five classes below each implement one of the clauses from the definition
// of INVOKE. The inner class template Accept<F, Args...> checks whether the
// clause is applicable; static function template Invoke(f, args...) does the
// invocation.
//
// By separating the clause selection logic from invocation we make sure that
// Invoke() does exactly what the standard says.
template <typename Derived>
struct StrippedAccept {
template <typename... Args>
struct Accept : Derived::template AcceptImpl<typename std::remove_cv<
typename std::remove_reference<Args>::type>::type...> {};
};
// (t1.*f)(t2, ..., tN) when f is a pointer to a member function of a class T
// and t1 is an object of type T or a reference to an object of type T or a
// reference to an object of a type derived from T.
struct MemFunAndRef : StrippedAccept<MemFunAndRef> {
template <typename... Args>
struct AcceptImpl : std::false_type {};
Export of internal Abseil changes -- f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e by Andy Soffer <asoffer@google.com>: Ensure that Invoke can support C++17 in the sense that noexcept is part of the type. PiperOrigin-RevId: 261730155 -- bf796ab71653a80498f9374bc8c5111d065c64ba by Abseil Team <absl-team@google.com>: Fix typo in static_assert message for copy/move constructible by replacing "by" with "be". PiperOrigin-RevId: 261713992 -- 8c7c17c40d03a322f304a2fd73ed34462dbf265a by Andy Soffer <asoffer@google.com>: Add absl::is_function drop-in replacement for std::is_function. Some standard libraries incorrectly implement std::is_function in a few corner cases. In particular, libstdc++ functions marked noexcept. The trick being used here is that function types decay to pointers. After excluding cases like is_class, etc, we can distinguish function types by testing for this decay. Many thanks to ericwf@ for essentially writing this CL. PiperOrigin-RevId: 261705008 -- c5adf42d0a132c2525d17a719329eab2ffe0aa94 by Abseil Team <absl-team@google.com>: Add microbenchmark for StrSplit that uses delimiter ByAnyChar. PiperOrigin-RevId: 261424010 -- 66a342f9381ec56be2fe3aa5b3193dd3538a9740 by Andy Soffer <asoffer@google.com>: CMake support for Abseil Random This change touches almost build-related files for CMake almost exclusively. The one minor exception is random/internal/salted_seed_seq.h. The default warnings configuration for one of our CI builds requests not having named but unused parameters. The change in this file cleans up that warning. PiperOrigin-RevId: 261192369 GitOrigin-RevId: f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e Change-Id: I05f662baacfe78750651535aa658f61c2327bc44
2019-08-05 20:32:04 +02:00
template <typename MemFunType, typename C, typename Obj, typename... Args>
struct AcceptImpl<MemFunType C::*, Obj, Args...>
: std::integral_constant<bool, std::is_base_of<C, Obj>::value &&
absl::is_function<MemFunType>::value> {
};
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template <typename MemFun, typename Obj, typename... Args>
static decltype((std::declval<Obj>().*
std::declval<MemFun>())(std::declval<Args>()...))
Invoke(MemFun&& mem_fun, Obj&& obj, Args&&... args) {
return (std::forward<Obj>(obj).*
std::forward<MemFun>(mem_fun))(std::forward<Args>(args)...);
}
};
// ((*t1).*f)(t2, ..., tN) when f is a pointer to a member function of a
// class T and t1 is not one of the types described in the previous item.
struct MemFunAndPtr : StrippedAccept<MemFunAndPtr> {
template <typename... Args>
struct AcceptImpl : std::false_type {};
Export of internal Abseil changes -- f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e by Andy Soffer <asoffer@google.com>: Ensure that Invoke can support C++17 in the sense that noexcept is part of the type. PiperOrigin-RevId: 261730155 -- bf796ab71653a80498f9374bc8c5111d065c64ba by Abseil Team <absl-team@google.com>: Fix typo in static_assert message for copy/move constructible by replacing "by" with "be". PiperOrigin-RevId: 261713992 -- 8c7c17c40d03a322f304a2fd73ed34462dbf265a by Andy Soffer <asoffer@google.com>: Add absl::is_function drop-in replacement for std::is_function. Some standard libraries incorrectly implement std::is_function in a few corner cases. In particular, libstdc++ functions marked noexcept. The trick being used here is that function types decay to pointers. After excluding cases like is_class, etc, we can distinguish function types by testing for this decay. Many thanks to ericwf@ for essentially writing this CL. PiperOrigin-RevId: 261705008 -- c5adf42d0a132c2525d17a719329eab2ffe0aa94 by Abseil Team <absl-team@google.com>: Add microbenchmark for StrSplit that uses delimiter ByAnyChar. PiperOrigin-RevId: 261424010 -- 66a342f9381ec56be2fe3aa5b3193dd3538a9740 by Andy Soffer <asoffer@google.com>: CMake support for Abseil Random This change touches almost build-related files for CMake almost exclusively. The one minor exception is random/internal/salted_seed_seq.h. The default warnings configuration for one of our CI builds requests not having named but unused parameters. The change in this file cleans up that warning. PiperOrigin-RevId: 261192369 GitOrigin-RevId: f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e Change-Id: I05f662baacfe78750651535aa658f61c2327bc44
2019-08-05 20:32:04 +02:00
template <typename MemFunType, typename C, typename Ptr, typename... Args>
struct AcceptImpl<MemFunType C::*, Ptr, Args...>
: std::integral_constant<bool, !std::is_base_of<C, Ptr>::value &&
absl::is_function<MemFunType>::value> {
};
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template <typename MemFun, typename Ptr, typename... Args>
static decltype(((*std::declval<Ptr>()).*
std::declval<MemFun>())(std::declval<Args>()...))
Invoke(MemFun&& mem_fun, Ptr&& ptr, Args&&... args) {
return ((*std::forward<Ptr>(ptr)).*
std::forward<MemFun>(mem_fun))(std::forward<Args>(args)...);
}
};
// t1.*f when N == 1 and f is a pointer to member data of a class T and t1 is
// an object of type T or a reference to an object of type T or a reference
// to an object of a type derived from T.
struct DataMemAndRef : StrippedAccept<DataMemAndRef> {
template <typename... Args>
struct AcceptImpl : std::false_type {};
template <typename R, typename C, typename Obj>
Export of internal Abseil changes -- f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e by Andy Soffer <asoffer@google.com>: Ensure that Invoke can support C++17 in the sense that noexcept is part of the type. PiperOrigin-RevId: 261730155 -- bf796ab71653a80498f9374bc8c5111d065c64ba by Abseil Team <absl-team@google.com>: Fix typo in static_assert message for copy/move constructible by replacing "by" with "be". PiperOrigin-RevId: 261713992 -- 8c7c17c40d03a322f304a2fd73ed34462dbf265a by Andy Soffer <asoffer@google.com>: Add absl::is_function drop-in replacement for std::is_function. Some standard libraries incorrectly implement std::is_function in a few corner cases. In particular, libstdc++ functions marked noexcept. The trick being used here is that function types decay to pointers. After excluding cases like is_class, etc, we can distinguish function types by testing for this decay. Many thanks to ericwf@ for essentially writing this CL. PiperOrigin-RevId: 261705008 -- c5adf42d0a132c2525d17a719329eab2ffe0aa94 by Abseil Team <absl-team@google.com>: Add microbenchmark for StrSplit that uses delimiter ByAnyChar. PiperOrigin-RevId: 261424010 -- 66a342f9381ec56be2fe3aa5b3193dd3538a9740 by Andy Soffer <asoffer@google.com>: CMake support for Abseil Random This change touches almost build-related files for CMake almost exclusively. The one minor exception is random/internal/salted_seed_seq.h. The default warnings configuration for one of our CI builds requests not having named but unused parameters. The change in this file cleans up that warning. PiperOrigin-RevId: 261192369 GitOrigin-RevId: f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e Change-Id: I05f662baacfe78750651535aa658f61c2327bc44
2019-08-05 20:32:04 +02:00
struct AcceptImpl<R C::*, Obj>
: std::integral_constant<bool, std::is_base_of<C, Obj>::value &&
!absl::is_function<R>::value> {};
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template <typename DataMem, typename Ref>
static decltype(std::declval<Ref>().*std::declval<DataMem>()) Invoke(
DataMem&& data_mem, Ref&& ref) {
return std::forward<Ref>(ref).*std::forward<DataMem>(data_mem);
}
};
// (*t1).*f when N == 1 and f is a pointer to member data of a class T and t1
// is not one of the types described in the previous item.
struct DataMemAndPtr : StrippedAccept<DataMemAndPtr> {
template <typename... Args>
struct AcceptImpl : std::false_type {};
template <typename R, typename C, typename Ptr>
struct AcceptImpl<R C::*, Ptr>
Export of internal Abseil changes -- f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e by Andy Soffer <asoffer@google.com>: Ensure that Invoke can support C++17 in the sense that noexcept is part of the type. PiperOrigin-RevId: 261730155 -- bf796ab71653a80498f9374bc8c5111d065c64ba by Abseil Team <absl-team@google.com>: Fix typo in static_assert message for copy/move constructible by replacing "by" with "be". PiperOrigin-RevId: 261713992 -- 8c7c17c40d03a322f304a2fd73ed34462dbf265a by Andy Soffer <asoffer@google.com>: Add absl::is_function drop-in replacement for std::is_function. Some standard libraries incorrectly implement std::is_function in a few corner cases. In particular, libstdc++ functions marked noexcept. The trick being used here is that function types decay to pointers. After excluding cases like is_class, etc, we can distinguish function types by testing for this decay. Many thanks to ericwf@ for essentially writing this CL. PiperOrigin-RevId: 261705008 -- c5adf42d0a132c2525d17a719329eab2ffe0aa94 by Abseil Team <absl-team@google.com>: Add microbenchmark for StrSplit that uses delimiter ByAnyChar. PiperOrigin-RevId: 261424010 -- 66a342f9381ec56be2fe3aa5b3193dd3538a9740 by Andy Soffer <asoffer@google.com>: CMake support for Abseil Random This change touches almost build-related files for CMake almost exclusively. The one minor exception is random/internal/salted_seed_seq.h. The default warnings configuration for one of our CI builds requests not having named but unused parameters. The change in this file cleans up that warning. PiperOrigin-RevId: 261192369 GitOrigin-RevId: f8fe0f483378c7520d8f8bdfabe4b20de4d96c7e Change-Id: I05f662baacfe78750651535aa658f61c2327bc44
2019-08-05 20:32:04 +02:00
: std::integral_constant<bool, !std::is_base_of<C, Ptr>::value &&
!absl::is_function<R>::value> {};
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template <typename DataMem, typename Ptr>
static decltype((*std::declval<Ptr>()).*std::declval<DataMem>()) Invoke(
DataMem&& data_mem, Ptr&& ptr) {
return (*std::forward<Ptr>(ptr)).*std::forward<DataMem>(data_mem);
}
};
// f(t1, t2, ..., tN) in all other cases.
struct Callable {
// Callable doesn't have Accept because it's the last clause that gets picked
// when none of the previous clauses are applicable.
template <typename F, typename... Args>
static decltype(std::declval<F>()(std::declval<Args>()...)) Invoke(
F&& f, Args&&... args) {
return std::forward<F>(f)(std::forward<Args>(args)...);
}
};
// Resolves to the first matching clause.
template <typename... Args>
struct Invoker {
typedef typename std::conditional<
MemFunAndRef::Accept<Args...>::value, MemFunAndRef,
typename std::conditional<
MemFunAndPtr::Accept<Args...>::value, MemFunAndPtr,
typename std::conditional<
DataMemAndRef::Accept<Args...>::value, DataMemAndRef,
typename std::conditional<DataMemAndPtr::Accept<Args...>::value,
DataMemAndPtr, Callable>::type>::type>::
type>::type type;
};
// The result type of Invoke<F, Args...>.
template <typename F, typename... Args>
using InvokeT = decltype(Invoker<F, Args...>::type::Invoke(
std::declval<F>(), std::declval<Args>()...));
// Invoke(f, args...) is an implementation of INVOKE(f, args...) from section
// [func.require] of the C++ standard.
template <typename F, typename... Args>
InvokeT<F, Args...> Invoke(F&& f, Args&&... args) {
return Invoker<F, Args...>::type::Invoke(std::forward<F>(f),
std::forward<Args>(args)...);
}
} // namespace base_internal
} // namespace absl
#endif // ABSL_BASE_INTERNAL_INVOKE_H_