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// 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/base/internal/invoke.h"
#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<T>::value>
struct PassByValue : std::false_type {};

template <typename T>
struct PassByValue<T, /*IsLValueReference=*/false>
    : std::integral_constant<bool,
                             absl::is_trivially_copy_constructible<T>::value &&
                                 absl::is_trivially_copy_assignable<
                                     typename std::remove_cv<T>::type>::value &&
                                 std::is_trivially_destructible<T>::value &&
                                 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) {
  auto o = static_cast<const Obj*>(ptr.obj);
  return static_cast<R>(
      absl::base_internal::invoke(*o, std::forward<Args>(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>(
      absl::base_internal::invoke(f, std::forward<Args>(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<C, int>::type;

}  // namespace functional_internal
ABSL_NAMESPACE_END
}  // namespace absl

#endif  // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_

	// 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/base/internal/invoke.h"
	#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<T>::value>
	struct PassByValue : std::false_type {};

	template <typename T>
	struct PassByValue<T, /IsLValueReference=/false>
	: std::integral_constant<bool,
	absl::is_trivially_copy_constructible<T>::value &&
	absl::is_trivially_copy_assignable<
	typename std::remove_cv<T>::type>::value &&
	std::is_trivially_destructible<T>::value &&
	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) {
	auto o = static_cast<const Obj*>(ptr.obj);
	return static_cast<R>(
	absl::base_internal::invoke(*o, std::forward<Args>(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>(
	absl::base_internal::invoke(f, std::forward<Args>(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<C, int>::type;

	} // namespace functional_internal
	ABSL_NAMESPACE_END
	} // namespace absl

	#endif // ABSL_FUNCTIONAL_INTERNAL_FUNCTION_REF_H_