/src/abseil-cpp/absl/functional/internal/function_ref.h

Source
// Copyright 2019 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
//
// 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.

#ifndef ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
#define ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_

#include <cassert>
#include <functional>
#include <type_traits>

#include "absl/functional/any_invocable.h"
#include "absl/meta/type_traits.h"

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace functional_internal {

// Like a void* that can handle function pointers as well. The standard does not
// allow function pointers to round-trip through void*, but void(*)() is fine.
//
// Note: It's important that this class remains trivial and is the same size as
// a pointer, since this allows the compiler to perform tail-call optimizations
// when the underlying function is a callable object with a matching signature.
union VoidPtr {
  const void* obj;
  void (*fun)();
};

// Chooses the best type for passing T as an argument.
// Attempt to be close to SystemV AMD64 ABI. Objects with trivial copy ctor are
// passed by value.
template <typename T, bool IsLValueReference = std::is_lvalue_reference_v<T>>
struct PassByValue : std::false_type {};

template <typename T>
struct PassByValue<T, /*IsLValueReference=*/false>
    : std::integral_constant<
          bool, std::is_trivially_copy_constructible_v<T> &&
                    std::is_trivially_copy_assignable_v<std::remove_cv_t<T>> &&
                    std::is_trivially_destructible_v<T> &&
                    sizeof(T) <= 2 * sizeof(void*)> {};

template <typename T>
struct ForwardT : std::conditional<PassByValue<T>::value, T, T&&> {};

// An Invoker takes a pointer to the type-erased invokable object, followed by
// the arguments that the invokable object expects.
//
// Note: The order of arguments here is an optimization, since member functions
// have an implicit "this" pointer as their first argument, putting VoidPtr
// first allows the compiler to perform tail-call optimization in many cases.
template <typename R, typename... Args>
using Invoker = R (*)(VoidPtr, typename ForwardT<Args>::type...);

//
// InvokeObject and InvokeFunction provide static "Invoke" functions that can be
// used as Invokers for objects or functions respectively.
//
// static_cast<R> handles the case the return type is void.
template <typename Obj, typename R, typename... Args>
R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) {
  using T = std::remove_reference_t<Obj>;
  return static_cast<R>(std::invoke(
      std::forward<Obj>(*const_cast<T*>(static_cast<const T*>(ptr.obj))),
      std::forward<typename ForwardT<Args>::type>(args)...));
}

template <typename Obj, typename Fun, Fun F, typename R, typename... Args>
R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) {
  using T = std::remove_reference_t<Obj>;
  Obj&& obj =
      std::forward<Obj>(*const_cast<T*>(static_cast<const T*>(ptr.obj)));
  // Avoid std::invoke() since the callee is a known function at compile time
  if constexpr (std::is_member_function_pointer_v<Fun>) {
    return static_cast<R>((std::forward<Obj>(obj).*F)(
        std::forward<typename ForwardT<Args>::type>(args)...));
  } else {
    return static_cast<R>(
        F(std::forward<Obj>(obj),
          std::forward<typename ForwardT<Args>::type>(args)...));
  }
}

template <typename T, typename Fun, Fun F, typename R, typename... Args>
R InvokePtr(VoidPtr ptr, typename ForwardT<Args>::type... args) {
  T* obj = const_cast<T*>(static_cast<const T*>(ptr.obj));
  // Avoid std::invoke() since the callee is a known function at compile time
  if constexpr (std::is_member_function_pointer_v<Fun>) {
    return static_cast<R>(
        (obj->*F)(std::forward<typename ForwardT<Args>::type>(args)...));
  } else {
    return static_cast<R>(
        F(obj, std::forward<typename ForwardT<Args>::type>(args)...));
  }
}

template <typename Fun, typename R, typename... Args>
R InvokeFunction(VoidPtr ptr, typename ForwardT<Args>::type... args) {
  auto f = reinterpret_cast<Fun>(ptr.fun);
  return static_cast<R>(
      std::invoke(f, std::forward<typename ForwardT<Args>::type>(args)...));
}

template <typename Fun, Fun F, typename R, typename... Args>
R InvokeFunction(VoidPtr, typename ForwardT<Args>::type... args) {
  return static_cast<R>(
      F(std::forward<typename ForwardT<Args>::type>(args)...));
}

template <typename Sig>
void AssertNonNull(const std::function<Sig>& f) {
  assert(f != nullptr);
  (void)f;
}

template <typename Sig>
void AssertNonNull(const AnyInvocable<Sig>& f) {
  assert(f != nullptr);
  (void)f;
}

template <typename F>
void AssertNonNull(const F&) {}

template <typename F, typename C>
void AssertNonNull(F C::* f) {
  assert(f != nullptr);
  (void)f;
}

template <bool C>
using EnableIf = typename ::std::enable_if_t<C, int>;

}  // namespace functional_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_

Line	Count	Source
1		// Copyright 2019 The Abseil Authors.
2		//
3		// Licensed under the Apache License, Version 2.0 (the "License");
4		// you may not use this file except in compliance with the License.
5		// You may obtain a copy of the License at
6		//
7		// https://www.apache.org/licenses/LICENSE-2.0
8		//
9		// Unless required by applicable law or agreed to in writing, software
10		// distributed under the License is distributed on an "AS IS" BASIS,
11		// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12		// See the License for the specific language governing permissions and
13		// limitations under the License.
14
15		#ifndef ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
16		#define ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_
17
18		#include <cassert>
19		#include <functional>
20		#include <type_traits>
21
22		#include "absl/functional/any_invocable.h"
23		#include "absl/meta/type_traits.h"
24
25		namespace absl {
26		ABSL_NAMESPACE_BEGIN
27		namespace functional_internal {
28
29		// Like a void* that can handle function pointers as well. The standard does not
30		// allow function pointers to round-trip through void, but void()() is fine.
31		//
32		// Note: It's important that this class remains trivial and is the same size as
33		// a pointer, since this allows the compiler to perform tail-call optimizations
34		// when the underlying function is a callable object with a matching signature.
35		union VoidPtr {
36		const void* obj;
37		void (*fun)();
38		};
39
40		// Chooses the best type for passing T as an argument.
41		// Attempt to be close to SystemV AMD64 ABI. Objects with trivial copy ctor are
42		// passed by value.
43		template <typename T, bool IsLValueReference = std::is_lvalue_reference_v<T>>
44		struct PassByValue : std::false_type {};
45
46		template <typename T>
47		struct PassByValue<T, /IsLValueReference=/false>
48		: std::integral_constant<
49		bool, std::is_trivially_copy_constructible_v<T> &&
50		std::is_trivially_copy_assignable_v<std::remove_cv_t<T>> &&
51		std::is_trivially_destructible_v<T> &&
52		sizeof(T) <= 2 * sizeof(void*)> {};
53
54		template <typename T>
55		struct ForwardT : std::conditional<PassByValue<T>::value, T, T&&> {};
56
57		// An Invoker takes a pointer to the type-erased invokable object, followed by
58		// the arguments that the invokable object expects.
59		//
60		// Note: The order of arguments here is an optimization, since member functions
61		// have an implicit "this" pointer as their first argument, putting VoidPtr
62		// first allows the compiler to perform tail-call optimization in many cases.
63		template <typename R, typename... Args>
64		using Invoker = R (*)(VoidPtr, typename ForwardT<Args>::type...);
65
66		//
67		// InvokeObject and InvokeFunction provide static "Invoke" functions that can be
68		// used as Invokers for objects or functions respectively.
69		//
70		// static_cast<R> handles the case the return type is void.
71		template <typename Obj, typename R, typename... Args>
72	0	R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) {
73	0	using T = std::remove_reference_t<Obj>;
74	0	return static_cast<R>(std::invoke(
75	0	std::forward<Obj>(const_cast<T>(static_cast<const T*>(ptr.obj))),
76	0	std::forward<typename ForwardT<Args>::type>(args)...));
77	0	} Unexecuted instantiation: void absl::functional_internal::InvokeObject<absl::Cord::HashFragmented<absl::hash_internal::MixingHashState>(absl::hash_internal::MixingHashState) const::{lambda(std::__1::basic_string_view<char, std::__1::char_traits<char> >)#1}&, void, std::__1::basic_string_view<char, std::__1::char_traits<char> > >(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<std::__1::basic_string_view<char, std::__1::char_traits<char> > >::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)>)::{lambda(absl::Span<unsigned int>)#1}&, void, absl::Span<unsigned int> >(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::Span<unsigned int> >::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatFPositiveExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&, bool)::$_0&, void, absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)>)::{lambda(absl::Span<unsigned int>)#1}&, void, absl::Span<unsigned int> >(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::Span<unsigned int> >::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatFNegativeExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0&, void, absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatEPositiveExpSlow(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0&, void, absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatENegativeExpSlow(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0&, void, absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatGPositiveExpSlow<absl::uint128>(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)#1}&, void, absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatGNegativeExpSlow<absl::uint128>(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)#1}&, void, absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatGPositiveExpSlow<unsigned long>(unsigned long, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)#1}&, void, absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal>::type) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::InvokeObject<absl::str_format_internal::(anonymous namespace)::FormatGNegativeExpSlow<unsigned long>(unsigned long, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)#1}&, void, absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>(absl::functional_internal::VoidPtr, absl::functional_internal::ForwardT<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator>::type)
78
79		template <typename Obj, typename Fun, Fun F, typename R, typename... Args>
80		R InvokeObject(VoidPtr ptr, typename ForwardT<Args>::type... args) {
81		using T = std::remove_reference_t<Obj>;
82		Obj&& obj =
83		std::forward<Obj>(const_cast<T>(static_cast<const T*>(ptr.obj)));
84		// Avoid std::invoke() since the callee is a known function at compile time
85		if constexpr (std::is_member_function_pointer_v<Fun>) {
86		return static_cast<R>((std::forward<Obj>(obj).*F)(
87		std::forward<typename ForwardT<Args>::type>(args)...));
88		} else {
89		return static_cast<R>(
90		F(std::forward<Obj>(obj),
91		std::forward<typename ForwardT<Args>::type>(args)...));
92		}
93		}
94
95		template <typename T, typename Fun, Fun F, typename R, typename... Args>
96		R InvokePtr(VoidPtr ptr, typename ForwardT<Args>::type... args) {
97		T* obj = const_cast<T>(static_cast<const T>(ptr.obj));
98		// Avoid std::invoke() since the callee is a known function at compile time
99		if constexpr (std::is_member_function_pointer_v<Fun>) {
100		return static_cast<R>(
101		(obj->*F)(std::forward<typename ForwardT<Args>::type>(args)...));
102		} else {
103		return static_cast<R>(
104		F(obj, std::forward<typename ForwardT<Args>::type>(args)...));
105		}
106		}
107
108		template <typename Fun, typename R, typename... Args>
109		R InvokeFunction(VoidPtr ptr, typename ForwardT<Args>::type... args) {
110		auto f = reinterpret_cast<Fun>(ptr.fun);
111		return static_cast<R>(
112		std::invoke(f, std::forward<typename ForwardT<Args>::type>(args)...));
113		}
114
115		template <typename Fun, Fun F, typename R, typename... Args>
116		R InvokeFunction(VoidPtr, typename ForwardT<Args>::type... args) {
117		return static_cast<R>(
118		F(std::forward<typename ForwardT<Args>::type>(args)...));
119		}
120
121		template <typename Sig>
122		void AssertNonNull(const std::function<Sig>& f) {
123		assert(f != nullptr);
124		(void)f;
125		}
126
127		template <typename Sig>
128		void AssertNonNull(const AnyInvocable<Sig>& f) {
129		assert(f != nullptr);
130		(void)f;
131		}
132
133		template <typename F>
134	0	void AssertNonNull(const F&) {} Unexecuted instantiation: void absl::functional_internal::AssertNonNull<absl::Cord::HashFragmented<absl::hash_internal::MixingHashState>(absl::hash_internal::MixingHashState) const::{lambda(std::__1::basic_string_view<char, std::__1::char_traits<char> >)#1}>(absl::Cord::HashFragmented<absl::hash_internal::MixingHashState>(absl::hash_internal::MixingHashState) const::{lambda(std::__1::basic_string_view<char, std::__1::char_traits<char> >)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::BinaryToDecimal::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)>)::{lambda(absl::Span<unsigned int>)#1}>(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)>)::{lambda(absl::Span<unsigned int>)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatFPositiveExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&, bool)::$_0>(absl::str_format_internal::(anonymous namespace)::FormatFPositiveExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&, bool)::$_0 const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)>)::{lambda(absl::Span<unsigned int>)#1}>(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator::RunConversion(absl::uint128, int, absl::FunctionRef<void (absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)>)::{lambda(absl::Span<unsigned int>)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatFNegativeExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0>(absl::str_format_internal::(anonymous namespace)::FormatFNegativeExpSlow(absl::uint128, int, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0 const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatEPositiveExpSlow(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0>(absl::str_format_internal::(anonymous namespace)::FormatEPositiveExpSlow(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0 const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatENegativeExpSlow(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0>(absl::str_format_internal::(anonymous namespace)::FormatENegativeExpSlow(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&, unsigned long)::$_0 const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatGPositiveExpSlow<absl::uint128>(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)#1}>(absl::str_format_internal::(anonymous namespace)::FormatGPositiveExpSlow<absl::uint128>(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatGNegativeExpSlow<absl::uint128>(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)#1}>(absl::str_format_internal::(anonymous namespace)::FormatGNegativeExpSlow<absl::uint128>(absl::uint128, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatGPositiveExpSlow<unsigned long>(unsigned long, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)#1}>(absl::str_format_internal::(anonymous namespace)::FormatGPositiveExpSlow<unsigned long>(unsigned long, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::BinaryToDecimal)#1} const&) Unexecuted instantiation: float_conversion.cc:void absl::functional_internal::AssertNonNull<absl::str_format_internal::(anonymous namespace)::FormatGNegativeExpSlow<unsigned long>(unsigned long, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)#1}>(absl::str_format_internal::(anonymous namespace)::FormatGNegativeExpSlow<unsigned long>(unsigned long, int, bool, absl::str_format_internal::(anonymous namespace)::FormatState const&)::{lambda(absl::str_format_internal::(anonymous namespace)::FractionalDigitGenerator)#1} const&)
135
136		template <typename F, typename C>
137		void AssertNonNull(F C::* f) {
138		assert(f != nullptr);
139		(void)f;
140		}
141
142		template <bool C>
143		using EnableIf = typename ::std::enable_if_t<C, int>;
144
145		} // namespace functional_internal
146		ABSL_NAMESPACE_END
147		} // namespace absl
148
149		#endif // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_

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Created: 2026-07-16 06:43