/*
* Copyright (C) 2016 Apple Inc. All rights reserved.
* Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
* Copyright (c) 2018-2023, Andreas Kling <kling@serenityos.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
* THE POSSIBILITY OF SUCH DAMAGE.
*/
#pragma once
#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/BitCast.h>
#include <AK/Noncopyable.h>
#include <AK/ScopeGuard.h>
#include <AK/Span.h>
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
namespace AK {
// These annotations are used to avoid capturing a variable with local storage in a lambda that outlives it
#if defined(AK_COMPILER_CLANG)
# define ESCAPING [[clang::annotate("minerva::escaping")]]
// FIXME: When we get C++23, change this to be applied to the lambda directly instead of to the types of its captures
# define IGNORE_USE_IN_ESCAPING_LAMBDA [[clang::annotate("minerva::ignore_use_in_escaping_lambda")]]
#else
# define ESCAPING
# define IGNORE_USE_IN_ESCAPING_LAMBDA
#endif
#ifdef AK_COMPILER_GCC
# pragma GCC diagnostic push
// FIXME: GCC does not like the union, thinking we access a zero-sized array out of bounds.
# pragma GCC diagnostic ignored "-Warray-bounds"
#endif
template<typename>
class Function;
template<typename F>
inline constexpr bool IsFunctionPointer = (IsPointer<F> && IsFunction<RemovePointer<F>>);
// Not a function pointer, and not an lvalue reference.
template<typename F>
inline constexpr bool IsFunctionObject = (!IsFunctionPointer<F> && IsRvalueReference<F&&>);
template<typename Out, typename... In>
class Function<Out(In...)> {
AK_MAKE_NONCOPYABLE(Function);
public:
using FunctionType = Out(In...);
using ReturnType = Out;
#ifdef KERNEL
constexpr static auto AccommodateExcessiveAlignmentRequirements = false;
constexpr static size_t ExcessiveAlignmentThreshold = alignof(void*);
#else
constexpr static auto AccommodateExcessiveAlignmentRequirements = true;
constexpr static size_t ExcessiveAlignmentThreshold = 16;
#endif
Function() = default;
Function(nullptr_t)
{
}
constexpr ~Function()
{
clear(false);
}
[[nodiscard]] ReadonlyBytes raw_capture_range() const
{
if (!m_size)
return {};
if (auto* wrapper = callable_wrapper())
return ReadonlyBytes { wrapper, m_size };
return {};
}
template<typename CallableType>
constexpr Function(CallableType&& callable)
requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, Out, In...> && !IsSame<RemoveCVReference<CallableType>, Function>))
{
init_with_callable(forward<CallableType>(callable), CallableKind::FunctionObject);
}
template<typename FunctionType>
constexpr Function(FunctionType f)
requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, Out, In...> && !IsSame<RemoveCVReference<FunctionType>, Function>))
{
init_with_callable(move(f), CallableKind::FunctionPointer);
}
Function(Function&& other)
{
move_from(move(other));
}
// Note: Despite this method being const, a mutable lambda _may_ modify its own captures.
constexpr Out operator()(In... in) const
{
auto* wrapper = callable_wrapper();
if (!is_constant_evaluated())
VERIFY(wrapper);
++m_call_nesting_level;
ScopeGuard guard([this] {
if (--m_call_nesting_level == 0 && m_deferred_clear)
const_cast<Function*>(this)->clear(false);
});
return wrapper->call(forward<In>(in)...);
}
explicit operator bool() const { return !!callable_wrapper(); }
template<typename CallableType>
constexpr Function& operator=(CallableType&& callable)
requires((IsFunctionObject<CallableType> && IsCallableWithArguments<CallableType, Out, In...>))
{
clear();
init_with_callable(forward<CallableType>(callable), CallableKind::FunctionObject);
return *this;
}
template<typename FunctionType>
constexpr Function& operator=(FunctionType f)
requires((IsFunctionPointer<FunctionType> && IsCallableWithArguments<RemovePointer<FunctionType>, Out, In...>))
{
clear();
if (f)
init_with_callable(move(f), CallableKind::FunctionPointer);
return *this;
}
Function& operator=(nullptr_t)
{
clear();
return *this;
}
Function& operator=(Function&& other)
{
if (this != &other) {
clear();
move_from(move(other));
}
return *this;
}
private:
enum class CallableKind {
FunctionPointer,
FunctionObject,
};
class CallableWrapperBase {
public:
virtual ~CallableWrapperBase() = default;
// Note: This is not const to allow storing mutable lambdas.
virtual constexpr Out call(In...) = 0;
virtual void init_and_swap(u8*, size_t) = 0;
};
template<typename CallableType>
class CallableWrapper final : public CallableWrapperBase {
AK_MAKE_NONMOVABLE(CallableWrapper);
AK_MAKE_NONCOPYABLE(CallableWrapper);
public:
explicit constexpr CallableWrapper(CallableType&& callable)
: m_callable(move(callable))
{
}
Out constexpr call(In... in) final override
{
return m_callable(forward<In>(in)...);
}
constexpr ~CallableWrapper() final override = default;
// NOLINTNEXTLINE(readability-non-const-parameter) False positive; destination is used in a placement new expression
void init_and_swap(u8* destination, size_t size) final override
{
VERIFY(size >= sizeof(CallableWrapper));
new (destination) CallableWrapper { move(m_callable) };
}
private:
CallableType m_callable;
};
enum class FunctionKind {
NullPointer,
Inline,
Outline,
};
constexpr CallableWrapperBase* callable_wrapper() const
{
switch (m_kind) {
case FunctionKind::NullPointer:
return nullptr;
case FunctionKind::Inline:
return bit_cast<CallableWrapperBase*>(&m_storage);
case FunctionKind::Outline:
return m_storage.wrapper;
default:
VERIFY_NOT_REACHED();
}
}
constexpr void clear(bool may_defer = true)
{
bool called_from_inside_function = m_call_nesting_level > 0;
// NOTE: This VERIFY could fail because a Function is destroyed from within itself.
VERIFY(may_defer || !called_from_inside_function);
if (called_from_inside_function && may_defer) {
m_deferred_clear = true;
return;
}
m_deferred_clear = false;
auto* wrapper = callable_wrapper();
if (m_kind == FunctionKind::Inline) {
VERIFY(wrapper);
wrapper->~CallableWrapperBase();
} else if (m_kind == FunctionKind::Outline) {
VERIFY(wrapper);
delete wrapper;
}
m_kind = FunctionKind::NullPointer;
}
template<typename Callable>
constexpr void init_with_callable(Callable&& callable, CallableKind callable_kind)
{
if constexpr (alignof(Callable) > ExcessiveAlignmentThreshold && !AccommodateExcessiveAlignmentRequirements) {
static_assert(
alignof(Callable) <= ExcessiveAlignmentThreshold,
"This callable object has a very large alignment requirement, "
"check your capture list if it is a lambda expression, "
"and make sure your callable object is not excessively aligned.");
}
if (!is_constant_evaluated())
VERIFY(m_call_nesting_level == 0);
using WrapperType = CallableWrapper<Callable>;
if (is_constant_evaluated()) {
m_storage.wrapper = new WrapperType(forward<Callable>(callable));
m_kind = FunctionKind::Outline;
} else {
#ifndef KERNEL
if constexpr (alignof(Callable) > inline_alignment || sizeof(WrapperType) > inline_capacity) {
m_storage.wrapper = new WrapperType(forward<Callable>(callable));
m_kind = FunctionKind::Outline;
} else {
#endif
static_assert(sizeof(WrapperType) <= inline_capacity);
new (m_storage.storage) WrapperType(forward<Callable>(callable));
m_kind = FunctionKind::Inline;
#ifndef KERNEL
}
#endif
}
if (callable_kind == CallableKind::FunctionObject)
m_size = sizeof(WrapperType);
else
m_size = 0;
}
void move_from(Function&& other)
{
VERIFY(m_call_nesting_level == 0 && other.m_call_nesting_level == 0);
auto* other_wrapper = other.callable_wrapper();
m_size = other.m_size;
switch (other.m_kind) {
case FunctionKind::NullPointer:
break;
case FunctionKind::Inline:
other_wrapper->init_and_swap(m_storage.storage, inline_capacity);
m_kind = FunctionKind::Inline;
break;
case FunctionKind::Outline:
m_storage.wrapper = other_wrapper;
m_kind = FunctionKind::Outline;
break;
default:
VERIFY_NOT_REACHED();
}
other.m_kind = FunctionKind::NullPointer;
}
size_t m_size { 0 };
FunctionKind m_kind { FunctionKind::NullPointer };
bool m_deferred_clear { false };
mutable Atomic<u16> m_call_nesting_level { 0 };
static constexpr size_t inline_alignment = max(alignof(CallableWrapperBase), alignof(CallableWrapperBase*));
#ifndef KERNEL
// Empirically determined to fit most lambdas and functions.
static constexpr size_t inline_capacity = 4 * sizeof(void*);
#else
// FIXME: Try to decrease this.
static constexpr size_t inline_capacity = 6 * sizeof(void*);
#endif
alignas(inline_alignment) union {
u8 storage[inline_capacity];
CallableWrapperBase* wrapper;
} m_storage;
};
}
#if USING_AK_GLOBALLY
using AK::Function;
using AK::IsCallableWithArguments;
#endif
#ifdef AK_COMPILER_GCC
# pragma GCC diagnostic pop
#endif
