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| -rw-r--r-- | security/sandbox/chromium/base/bind_internal.h | 1050 |
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diff --git a/security/sandbox/chromium/base/bind_internal.h b/security/sandbox/chromium/base/bind_internal.h new file mode 100644 index 0000000000..bed151a8dc --- /dev/null +++ b/security/sandbox/chromium/base/bind_internal.h @@ -0,0 +1,1050 @@ +// Copyright (c) 2011 The Chromium Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. + +#ifndef BASE_BIND_INTERNAL_H_ +#define BASE_BIND_INTERNAL_H_ + +#include <stddef.h> + +#include <functional> +#include <memory> +#include <tuple> +#include <type_traits> +#include <utility> + +#include "base/bind.h" +#include "base/callback_internal.h" +#include "base/compiler_specific.h" +#include "base/memory/raw_scoped_refptr_mismatch_checker.h" +#include "base/memory/weak_ptr.h" +#include "base/template_util.h" +#include "build/build_config.h" + +#if defined(OS_MACOSX) && !HAS_FEATURE(objc_arc) +#include "base/mac/scoped_block.h" +#endif + +// See base/callback.h for user documentation. +// +// +// CONCEPTS: +// Functor -- A movable type representing something that should be called. +// All function pointers and Callback<> are functors even if the +// invocation syntax differs. +// RunType -- A function type (as opposed to function _pointer_ type) for +// a Callback<>::Run(). Usually just a convenience typedef. +// (Bound)Args -- A set of types that stores the arguments. +// +// Types: +// ForceVoidReturn<> -- Helper class for translating function signatures to +// equivalent forms with a "void" return type. +// FunctorTraits<> -- Type traits used to determine the correct RunType and +// invocation manner for a Functor. This is where function +// signature adapters are applied. +// InvokeHelper<> -- Take a Functor + arguments and actully invokes it. +// Handle the differing syntaxes needed for WeakPtr<> +// support. This is separate from Invoker to avoid creating +// multiple version of Invoker<>. +// Invoker<> -- Unwraps the curried parameters and executes the Functor. +// BindState<> -- Stores the curried parameters, and is the main entry point +// into the Bind() system. + +#if defined(OS_WIN) +namespace Microsoft { +namespace WRL { +template <typename> +class ComPtr; +} // namespace WRL +} // namespace Microsoft +#endif + +namespace base { + +template <typename T> +struct IsWeakReceiver; + +template <typename> +struct BindUnwrapTraits; + +template <typename Functor, typename BoundArgsTuple, typename SFINAE = void> +struct CallbackCancellationTraits; + +namespace internal { + +template <typename Functor, typename SFINAE = void> +struct FunctorTraits; + +template <typename T> +class UnretainedWrapper { + public: + explicit UnretainedWrapper(T* o) : ptr_(o) {} + T* get() const { return ptr_; } + + private: + T* ptr_; +}; + +template <typename T> +class RetainedRefWrapper { + public: + explicit RetainedRefWrapper(T* o) : ptr_(o) {} + explicit RetainedRefWrapper(scoped_refptr<T> o) : ptr_(std::move(o)) {} + T* get() const { return ptr_.get(); } + + private: + scoped_refptr<T> ptr_; +}; + +template <typename T> +struct IgnoreResultHelper { + explicit IgnoreResultHelper(T functor) : functor_(std::move(functor)) {} + explicit operator bool() const { return !!functor_; } + + T functor_; +}; + +template <typename T, typename Deleter = std::default_delete<T>> +class OwnedWrapper { + public: + explicit OwnedWrapper(T* o) : ptr_(o) {} + explicit OwnedWrapper(std::unique_ptr<T, Deleter>&& ptr) + : ptr_(std::move(ptr)) {} + T* get() const { return ptr_.get(); } + + private: + std::unique_ptr<T, Deleter> ptr_; +}; + +// PassedWrapper is a copyable adapter for a scoper that ignores const. +// +// It is needed to get around the fact that Bind() takes a const reference to +// all its arguments. Because Bind() takes a const reference to avoid +// unnecessary copies, it is incompatible with movable-but-not-copyable +// types; doing a destructive "move" of the type into Bind() would violate +// the const correctness. +// +// This conundrum cannot be solved without either C++11 rvalue references or +// a O(2^n) blowup of Bind() templates to handle each combination of regular +// types and movable-but-not-copyable types. Thus we introduce a wrapper type +// that is copyable to transmit the correct type information down into +// BindState<>. Ignoring const in this type makes sense because it is only +// created when we are explicitly trying to do a destructive move. +// +// Two notes: +// 1) PassedWrapper supports any type that has a move constructor, however +// the type will need to be specifically whitelisted in order for it to be +// bound to a Callback. We guard this explicitly at the call of Passed() +// to make for clear errors. Things not given to Passed() will be forwarded +// and stored by value which will not work for general move-only types. +// 2) is_valid_ is distinct from NULL because it is valid to bind a "NULL" +// scoper to a Callback and allow the Callback to execute once. +template <typename T> +class PassedWrapper { + public: + explicit PassedWrapper(T&& scoper) + : is_valid_(true), scoper_(std::move(scoper)) {} + PassedWrapper(PassedWrapper&& other) + : is_valid_(other.is_valid_), scoper_(std::move(other.scoper_)) {} + T Take() const { + CHECK(is_valid_); + is_valid_ = false; + return std::move(scoper_); + } + + private: + mutable bool is_valid_; + mutable T scoper_; +}; + +template <typename T> +using Unwrapper = BindUnwrapTraits<std::decay_t<T>>; + +template <typename T> +decltype(auto) Unwrap(T&& o) { + return Unwrapper<T>::Unwrap(std::forward<T>(o)); +} + +// IsWeakMethod is a helper that determine if we are binding a WeakPtr<> to a +// method. It is used internally by Bind() to select the correct +// InvokeHelper that will no-op itself in the event the WeakPtr<> for +// the target object is invalidated. +// +// The first argument should be the type of the object that will be received by +// the method. +template <bool is_method, typename... Args> +struct IsWeakMethod : std::false_type {}; + +template <typename T, typename... Args> +struct IsWeakMethod<true, T, Args...> : IsWeakReceiver<T> {}; + +// Packs a list of types to hold them in a single type. +template <typename... Types> +struct TypeList {}; + +// Used for DropTypeListItem implementation. +template <size_t n, typename List> +struct DropTypeListItemImpl; + +// Do not use enable_if and SFINAE here to avoid MSVC2013 compile failure. +template <size_t n, typename T, typename... List> +struct DropTypeListItemImpl<n, TypeList<T, List...>> + : DropTypeListItemImpl<n - 1, TypeList<List...>> {}; + +template <typename T, typename... List> +struct DropTypeListItemImpl<0, TypeList<T, List...>> { + using Type = TypeList<T, List...>; +}; + +template <> +struct DropTypeListItemImpl<0, TypeList<>> { + using Type = TypeList<>; +}; + +// A type-level function that drops |n| list item from given TypeList. +template <size_t n, typename List> +using DropTypeListItem = typename DropTypeListItemImpl<n, List>::Type; + +// Used for TakeTypeListItem implementation. +template <size_t n, typename List, typename... Accum> +struct TakeTypeListItemImpl; + +// Do not use enable_if and SFINAE here to avoid MSVC2013 compile failure. +template <size_t n, typename T, typename... List, typename... Accum> +struct TakeTypeListItemImpl<n, TypeList<T, List...>, Accum...> + : TakeTypeListItemImpl<n - 1, TypeList<List...>, Accum..., T> {}; + +template <typename T, typename... List, typename... Accum> +struct TakeTypeListItemImpl<0, TypeList<T, List...>, Accum...> { + using Type = TypeList<Accum...>; +}; + +template <typename... Accum> +struct TakeTypeListItemImpl<0, TypeList<>, Accum...> { + using Type = TypeList<Accum...>; +}; + +// A type-level function that takes first |n| list item from given TypeList. +// E.g. TakeTypeListItem<3, TypeList<A, B, C, D>> is evaluated to +// TypeList<A, B, C>. +template <size_t n, typename List> +using TakeTypeListItem = typename TakeTypeListItemImpl<n, List>::Type; + +// Used for ConcatTypeLists implementation. +template <typename List1, typename List2> +struct ConcatTypeListsImpl; + +template <typename... Types1, typename... Types2> +struct ConcatTypeListsImpl<TypeList<Types1...>, TypeList<Types2...>> { + using Type = TypeList<Types1..., Types2...>; +}; + +// A type-level function that concats two TypeLists. +template <typename List1, typename List2> +using ConcatTypeLists = typename ConcatTypeListsImpl<List1, List2>::Type; + +// Used for MakeFunctionType implementation. +template <typename R, typename ArgList> +struct MakeFunctionTypeImpl; + +template <typename R, typename... Args> +struct MakeFunctionTypeImpl<R, TypeList<Args...>> { + // MSVC 2013 doesn't support Type Alias of function types. + // Revisit this after we update it to newer version. + typedef R Type(Args...); +}; + +// A type-level function that constructs a function type that has |R| as its +// return type and has TypeLists items as its arguments. +template <typename R, typename ArgList> +using MakeFunctionType = typename MakeFunctionTypeImpl<R, ArgList>::Type; + +// Used for ExtractArgs and ExtractReturnType. +template <typename Signature> +struct ExtractArgsImpl; + +template <typename R, typename... Args> +struct ExtractArgsImpl<R(Args...)> { + using ReturnType = R; + using ArgsList = TypeList<Args...>; +}; + +// A type-level function that extracts function arguments into a TypeList. +// E.g. ExtractArgs<R(A, B, C)> is evaluated to TypeList<A, B, C>. +template <typename Signature> +using ExtractArgs = typename ExtractArgsImpl<Signature>::ArgsList; + +// A type-level function that extracts the return type of a function. +// E.g. ExtractReturnType<R(A, B, C)> is evaluated to R. +template <typename Signature> +using ExtractReturnType = typename ExtractArgsImpl<Signature>::ReturnType; + +template <typename Callable, + typename Signature = decltype(&Callable::operator())> +struct ExtractCallableRunTypeImpl; + +template <typename Callable, typename R, typename... Args> +struct ExtractCallableRunTypeImpl<Callable, R (Callable::*)(Args...)> { + using Type = R(Args...); +}; + +template <typename Callable, typename R, typename... Args> +struct ExtractCallableRunTypeImpl<Callable, R (Callable::*)(Args...) const> { + using Type = R(Args...); +}; + +// Evaluated to RunType of the given callable type. +// Example: +// auto f = [](int, char*) { return 0.1; }; +// ExtractCallableRunType<decltype(f)> +// is evaluated to +// double(int, char*); +template <typename Callable> +using ExtractCallableRunType = + typename ExtractCallableRunTypeImpl<Callable>::Type; + +// IsCallableObject<Functor> is std::true_type if |Functor| has operator(). +// Otherwise, it's std::false_type. +// Example: +// IsCallableObject<void(*)()>::value is false. +// +// struct Foo {}; +// IsCallableObject<void(Foo::*)()>::value is false. +// +// int i = 0; +// auto f = [i]() {}; +// IsCallableObject<decltype(f)>::value is false. +template <typename Functor, typename SFINAE = void> +struct IsCallableObject : std::false_type {}; + +template <typename Callable> +struct IsCallableObject<Callable, void_t<decltype(&Callable::operator())>> + : std::true_type {}; + +// HasRefCountedTypeAsRawPtr selects true_type when any of the |Args| is a raw +// pointer to a RefCounted type. +// Implementation note: This non-specialized case handles zero-arity case only. +// Non-zero-arity cases should be handled by the specialization below. +template <typename... Args> +struct HasRefCountedTypeAsRawPtr : std::false_type {}; + +// Implementation note: Select true_type if the first parameter is a raw pointer +// to a RefCounted type. Otherwise, skip the first parameter and check rest of +// parameters recursively. +template <typename T, typename... Args> +struct HasRefCountedTypeAsRawPtr<T, Args...> + : std::conditional_t<NeedsScopedRefptrButGetsRawPtr<T>::value, + std::true_type, + HasRefCountedTypeAsRawPtr<Args...>> {}; + +// ForceVoidReturn<> +// +// Set of templates that support forcing the function return type to void. +template <typename Sig> +struct ForceVoidReturn; + +template <typename R, typename... Args> +struct ForceVoidReturn<R(Args...)> { + using RunType = void(Args...); +}; + +// FunctorTraits<> +// +// See description at top of file. +template <typename Functor, typename SFINAE> +struct FunctorTraits; + +// For empty callable types. +// This specialization is intended to allow binding captureless lambdas, based +// on the fact that captureless lambdas are empty while capturing lambdas are +// not. This also allows any functors as far as it's an empty class. +// Example: +// +// // Captureless lambdas are allowed. +// []() {return 42;}; +// +// // Capturing lambdas are *not* allowed. +// int x; +// [x]() {return x;}; +// +// // Any empty class with operator() is allowed. +// struct Foo { +// void operator()() const {} +// // No non-static member variable and no virtual functions. +// }; +template <typename Functor> +struct FunctorTraits<Functor, + std::enable_if_t<IsCallableObject<Functor>::value && + std::is_empty<Functor>::value>> { + using RunType = ExtractCallableRunType<Functor>; + static constexpr bool is_method = false; + static constexpr bool is_nullable = false; + + template <typename RunFunctor, typename... RunArgs> + static ExtractReturnType<RunType> Invoke(RunFunctor&& functor, + RunArgs&&... args) { + return std::forward<RunFunctor>(functor)(std::forward<RunArgs>(args)...); + } +}; + +// For functions. +template <typename R, typename... Args> +struct FunctorTraits<R (*)(Args...)> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename Function, typename... RunArgs> + static R Invoke(Function&& function, RunArgs&&... args) { + return std::forward<Function>(function)(std::forward<RunArgs>(args)...); + } +}; + +#if defined(OS_WIN) && !defined(ARCH_CPU_64_BITS) + +// For functions. +template <typename R, typename... Args> +struct FunctorTraits<R(__stdcall*)(Args...)> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename... RunArgs> + static R Invoke(R(__stdcall* function)(Args...), RunArgs&&... args) { + return function(std::forward<RunArgs>(args)...); + } +}; + +// For functions. +template <typename R, typename... Args> +struct FunctorTraits<R(__fastcall*)(Args...)> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename... RunArgs> + static R Invoke(R(__fastcall* function)(Args...), RunArgs&&... args) { + return function(std::forward<RunArgs>(args)...); + } +}; + +#endif // defined(OS_WIN) && !defined(ARCH_CPU_64_BITS) + +#if defined(OS_MACOSX) + +// Support for Objective-C blocks. There are two implementation depending +// on whether Automated Reference Counting (ARC) is enabled. When ARC is +// enabled, then the block itself can be bound as the compiler will ensure +// its lifetime will be correctly managed. Otherwise, require the block to +// be wrapped in a base::mac::ScopedBlock (via base::RetainBlock) that will +// correctly manage the block lifetime. +// +// The two implementation ensure that the One Definition Rule (ODR) is not +// broken (it is not possible to write a template base::RetainBlock that would +// work correctly both with ARC enabled and disabled). + +#if HAS_FEATURE(objc_arc) + +template <typename R, typename... Args> +struct FunctorTraits<R (^)(Args...)> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename BlockType, typename... RunArgs> + static R Invoke(BlockType&& block, RunArgs&&... args) { + // According to LLVM documentation (ยง 6.3), "local variables of automatic + // storage duration do not have precise lifetime." Use objc_precise_lifetime + // to ensure that the Objective-C block is not deallocated until it has + // finished executing even if the Callback<> is destroyed during the block + // execution. + // https://clang.llvm.org/docs/AutomaticReferenceCounting.html#precise-lifetime-semantics + __attribute__((objc_precise_lifetime)) R (^scoped_block)(Args...) = block; + return scoped_block(std::forward<RunArgs>(args)...); + } +}; + +#else // HAS_FEATURE(objc_arc) + +template <typename R, typename... Args> +struct FunctorTraits<base::mac::ScopedBlock<R (^)(Args...)>> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename BlockType, typename... RunArgs> + static R Invoke(BlockType&& block, RunArgs&&... args) { + // Copy the block to ensure that the Objective-C block is not deallocated + // until it has finished executing even if the Callback<> is destroyed + // during the block execution. + base::mac::ScopedBlock<R (^)(Args...)> scoped_block(block); + return scoped_block.get()(std::forward<RunArgs>(args)...); + } +}; + +#endif // HAS_FEATURE(objc_arc) +#endif // defined(OS_MACOSX) + +// For methods. +template <typename R, typename Receiver, typename... Args> +struct FunctorTraits<R (Receiver::*)(Args...)> { + using RunType = R(Receiver*, Args...); + static constexpr bool is_method = true; + static constexpr bool is_nullable = true; + + template <typename Method, typename ReceiverPtr, typename... RunArgs> + static R Invoke(Method method, + ReceiverPtr&& receiver_ptr, + RunArgs&&... args) { + return ((*receiver_ptr).*method)(std::forward<RunArgs>(args)...); + } +}; + +// For const methods. +template <typename R, typename Receiver, typename... Args> +struct FunctorTraits<R (Receiver::*)(Args...) const> { + using RunType = R(const Receiver*, Args...); + static constexpr bool is_method = true; + static constexpr bool is_nullable = true; + + template <typename Method, typename ReceiverPtr, typename... RunArgs> + static R Invoke(Method method, + ReceiverPtr&& receiver_ptr, + RunArgs&&... args) { + return ((*receiver_ptr).*method)(std::forward<RunArgs>(args)...); + } +}; + +#ifdef __cpp_noexcept_function_type +// noexcept makes a distinct function type in C++17. +// I.e. `void(*)()` and `void(*)() noexcept` are same in pre-C++17, and +// different in C++17. +template <typename R, typename... Args> +struct FunctorTraits<R (*)(Args...) noexcept> : FunctorTraits<R (*)(Args...)> { +}; + +template <typename R, typename Receiver, typename... Args> +struct FunctorTraits<R (Receiver::*)(Args...) noexcept> + : FunctorTraits<R (Receiver::*)(Args...)> {}; + +template <typename R, typename Receiver, typename... Args> +struct FunctorTraits<R (Receiver::*)(Args...) const noexcept> + : FunctorTraits<R (Receiver::*)(Args...) const> {}; +#endif + +// For IgnoreResults. +template <typename T> +struct FunctorTraits<IgnoreResultHelper<T>> : FunctorTraits<T> { + using RunType = + typename ForceVoidReturn<typename FunctorTraits<T>::RunType>::RunType; + + template <typename IgnoreResultType, typename... RunArgs> + static void Invoke(IgnoreResultType&& ignore_result_helper, + RunArgs&&... args) { + FunctorTraits<T>::Invoke( + std::forward<IgnoreResultType>(ignore_result_helper).functor_, + std::forward<RunArgs>(args)...); + } +}; + +// For OnceCallbacks. +template <typename R, typename... Args> +struct FunctorTraits<OnceCallback<R(Args...)>> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename CallbackType, typename... RunArgs> + static R Invoke(CallbackType&& callback, RunArgs&&... args) { + DCHECK(!callback.is_null()); + return std::forward<CallbackType>(callback).Run( + std::forward<RunArgs>(args)...); + } +}; + +// For RepeatingCallbacks. +template <typename R, typename... Args> +struct FunctorTraits<RepeatingCallback<R(Args...)>> { + using RunType = R(Args...); + static constexpr bool is_method = false; + static constexpr bool is_nullable = true; + + template <typename CallbackType, typename... RunArgs> + static R Invoke(CallbackType&& callback, RunArgs&&... args) { + DCHECK(!callback.is_null()); + return std::forward<CallbackType>(callback).Run( + std::forward<RunArgs>(args)...); + } +}; + +template <typename Functor> +using MakeFunctorTraits = FunctorTraits<std::decay_t<Functor>>; + +// InvokeHelper<> +// +// There are 2 logical InvokeHelper<> specializations: normal, WeakCalls. +// +// The normal type just calls the underlying runnable. +// +// WeakCalls need special syntax that is applied to the first argument to check +// if they should no-op themselves. +template <bool is_weak_call, typename ReturnType> +struct InvokeHelper; + +template <typename ReturnType> +struct InvokeHelper<false, ReturnType> { + template <typename Functor, typename... RunArgs> + static inline ReturnType MakeItSo(Functor&& functor, RunArgs&&... args) { + using Traits = MakeFunctorTraits<Functor>; + return Traits::Invoke(std::forward<Functor>(functor), + std::forward<RunArgs>(args)...); + } +}; + +template <typename ReturnType> +struct InvokeHelper<true, ReturnType> { + // WeakCalls are only supported for functions with a void return type. + // Otherwise, the function result would be undefined if the the WeakPtr<> + // is invalidated. + static_assert(std::is_void<ReturnType>::value, + "weak_ptrs can only bind to methods without return values"); + + template <typename Functor, typename BoundWeakPtr, typename... RunArgs> + static inline void MakeItSo(Functor&& functor, + BoundWeakPtr&& weak_ptr, + RunArgs&&... args) { + if (!weak_ptr) + return; + using Traits = MakeFunctorTraits<Functor>; + Traits::Invoke(std::forward<Functor>(functor), + std::forward<BoundWeakPtr>(weak_ptr), + std::forward<RunArgs>(args)...); + } +}; + +// Invoker<> +// +// See description at the top of the file. +template <typename StorageType, typename UnboundRunType> +struct Invoker; + +template <typename StorageType, typename R, typename... UnboundArgs> +struct Invoker<StorageType, R(UnboundArgs...)> { + static R RunOnce(BindStateBase* base, + PassingType<UnboundArgs>... unbound_args) { + // Local references to make debugger stepping easier. If in a debugger, + // you really want to warp ahead and step through the + // InvokeHelper<>::MakeItSo() call below. + StorageType* storage = static_cast<StorageType*>(base); + static constexpr size_t num_bound_args = + std::tuple_size<decltype(storage->bound_args_)>::value; + return RunImpl(std::move(storage->functor_), + std::move(storage->bound_args_), + std::make_index_sequence<num_bound_args>(), + std::forward<UnboundArgs>(unbound_args)...); + } + + static R Run(BindStateBase* base, PassingType<UnboundArgs>... unbound_args) { + // Local references to make debugger stepping easier. If in a debugger, + // you really want to warp ahead and step through the + // InvokeHelper<>::MakeItSo() call below. + const StorageType* storage = static_cast<StorageType*>(base); + static constexpr size_t num_bound_args = + std::tuple_size<decltype(storage->bound_args_)>::value; + return RunImpl(storage->functor_, storage->bound_args_, + std::make_index_sequence<num_bound_args>(), + std::forward<UnboundArgs>(unbound_args)...); + } + + private: + template <typename Functor, typename BoundArgsTuple, size_t... indices> + static inline R RunImpl(Functor&& functor, + BoundArgsTuple&& bound, + std::index_sequence<indices...>, + UnboundArgs&&... unbound_args) { + static constexpr bool is_method = MakeFunctorTraits<Functor>::is_method; + + using DecayedArgsTuple = std::decay_t<BoundArgsTuple>; + static constexpr bool is_weak_call = + IsWeakMethod<is_method, + std::tuple_element_t<indices, DecayedArgsTuple>...>(); + + return InvokeHelper<is_weak_call, R>::MakeItSo( + std::forward<Functor>(functor), + Unwrap(std::get<indices>(std::forward<BoundArgsTuple>(bound)))..., + std::forward<UnboundArgs>(unbound_args)...); + } +}; + +// Extracts necessary type info from Functor and BoundArgs. +// Used to implement MakeUnboundRunType, BindOnce and BindRepeating. +template <typename Functor, typename... BoundArgs> +struct BindTypeHelper { + static constexpr size_t num_bounds = sizeof...(BoundArgs); + using FunctorTraits = MakeFunctorTraits<Functor>; + + // Example: + // When Functor is `double (Foo::*)(int, const std::string&)`, and BoundArgs + // is a template pack of `Foo*` and `int16_t`: + // - RunType is `double(Foo*, int, const std::string&)`, + // - ReturnType is `double`, + // - RunParamsList is `TypeList<Foo*, int, const std::string&>`, + // - BoundParamsList is `TypeList<Foo*, int>`, + // - UnboundParamsList is `TypeList<const std::string&>`, + // - BoundArgsList is `TypeList<Foo*, int16_t>`, + // - UnboundRunType is `double(const std::string&)`. + using RunType = typename FunctorTraits::RunType; + using ReturnType = ExtractReturnType<RunType>; + + using RunParamsList = ExtractArgs<RunType>; + using BoundParamsList = TakeTypeListItem<num_bounds, RunParamsList>; + using UnboundParamsList = DropTypeListItem<num_bounds, RunParamsList>; + + using BoundArgsList = TypeList<BoundArgs...>; + + using UnboundRunType = MakeFunctionType<ReturnType, UnboundParamsList>; +}; + +template <typename Functor> +std::enable_if_t<FunctorTraits<Functor>::is_nullable, bool> IsNull( + const Functor& functor) { + return !functor; +} + +template <typename Functor> +std::enable_if_t<!FunctorTraits<Functor>::is_nullable, bool> IsNull( + const Functor&) { + return false; +} + +// Used by QueryCancellationTraits below. +template <typename Functor, typename BoundArgsTuple, size_t... indices> +bool QueryCancellationTraitsImpl(BindStateBase::CancellationQueryMode mode, + const Functor& functor, + const BoundArgsTuple& bound_args, + std::index_sequence<indices...>) { + switch (mode) { + case BindStateBase::IS_CANCELLED: + return CallbackCancellationTraits<Functor, BoundArgsTuple>::IsCancelled( + functor, std::get<indices>(bound_args)...); + case BindStateBase::MAYBE_VALID: + return CallbackCancellationTraits<Functor, BoundArgsTuple>::MaybeValid( + functor, std::get<indices>(bound_args)...); + } + NOTREACHED(); +} + +// Relays |base| to corresponding CallbackCancellationTraits<>::Run(). Returns +// true if the callback |base| represents is canceled. +template <typename BindStateType> +bool QueryCancellationTraits(const BindStateBase* base, + BindStateBase::CancellationQueryMode mode) { + const BindStateType* storage = static_cast<const BindStateType*>(base); + static constexpr size_t num_bound_args = + std::tuple_size<decltype(storage->bound_args_)>::value; + return QueryCancellationTraitsImpl( + mode, storage->functor_, storage->bound_args_, + std::make_index_sequence<num_bound_args>()); +} + +// The base case of BanUnconstructedRefCountedReceiver that checks nothing. +template <typename Functor, typename Receiver, typename... Unused> +std::enable_if_t< + !(MakeFunctorTraits<Functor>::is_method && + std::is_pointer<std::decay_t<Receiver>>::value && + IsRefCountedType<std::remove_pointer_t<std::decay_t<Receiver>>>::value)> +BanUnconstructedRefCountedReceiver(const Receiver& receiver, Unused&&...) {} + +template <typename Functor> +void BanUnconstructedRefCountedReceiver() {} + +// Asserts that Callback is not the first owner of a ref-counted receiver. +template <typename Functor, typename Receiver, typename... Unused> +std::enable_if_t< + MakeFunctorTraits<Functor>::is_method && + std::is_pointer<std::decay_t<Receiver>>::value && + IsRefCountedType<std::remove_pointer_t<std::decay_t<Receiver>>>::value> +BanUnconstructedRefCountedReceiver(const Receiver& receiver, Unused&&...) { + DCHECK(receiver); + + // It's error prone to make the implicit first reference to ref-counted types. + // In the example below, base::BindOnce() makes the implicit first reference + // to the ref-counted Foo. If PostTask() failed or the posted task ran fast + // enough, the newly created instance can be destroyed before |oo| makes + // another reference. + // Foo::Foo() { + // base::PostTask(FROM_HERE, base::BindOnce(&Foo::Bar, this)); + // } + // + // scoped_refptr<Foo> oo = new Foo(); + // + // Instead of doing like above, please consider adding a static constructor, + // and keep the first reference alive explicitly. + // // static + // scoped_refptr<Foo> Foo::Create() { + // auto foo = base::WrapRefCounted(new Foo()); + // base::PostTask(FROM_HERE, base::BindOnce(&Foo::Bar, foo)); + // return foo; + // } + // + // Foo::Foo() {} + // + // scoped_refptr<Foo> oo = Foo::Create(); + DCHECK(receiver->HasAtLeastOneRef()) + << "base::Bind{Once,Repeating}() refuses to create the first reference " + "to ref-counted objects. That typically happens around PostTask() in " + "their constructor, and such objects can be destroyed before `new` " + "returns if the task resolves fast enough."; +} + +// BindState<> +// +// This stores all the state passed into Bind(). +template <typename Functor, typename... BoundArgs> +struct BindState final : BindStateBase { + using IsCancellable = std::integral_constant< + bool, + CallbackCancellationTraits<Functor, + std::tuple<BoundArgs...>>::is_cancellable>; + + template <typename ForwardFunctor, typename... ForwardBoundArgs> + static BindState* Create(BindStateBase::InvokeFuncStorage invoke_func, + ForwardFunctor&& functor, + ForwardBoundArgs&&... bound_args) { + // Ban ref counted receivers that were not yet fully constructed to avoid + // a common pattern of racy situation. + BanUnconstructedRefCountedReceiver<ForwardFunctor>(bound_args...); + + // IsCancellable is std::false_type if + // CallbackCancellationTraits<>::IsCancelled returns always false. + // Otherwise, it's std::true_type. + return new BindState(IsCancellable{}, invoke_func, + std::forward<ForwardFunctor>(functor), + std::forward<ForwardBoundArgs>(bound_args)...); + } + + Functor functor_; + std::tuple<BoundArgs...> bound_args_; + + private: + template <typename ForwardFunctor, typename... ForwardBoundArgs> + explicit BindState(std::true_type, + BindStateBase::InvokeFuncStorage invoke_func, + ForwardFunctor&& functor, + ForwardBoundArgs&&... bound_args) + : BindStateBase(invoke_func, + &Destroy, + &QueryCancellationTraits<BindState>), + functor_(std::forward<ForwardFunctor>(functor)), + bound_args_(std::forward<ForwardBoundArgs>(bound_args)...) { + DCHECK(!IsNull(functor_)); + } + + template <typename ForwardFunctor, typename... ForwardBoundArgs> + explicit BindState(std::false_type, + BindStateBase::InvokeFuncStorage invoke_func, + ForwardFunctor&& functor, + ForwardBoundArgs&&... bound_args) + : BindStateBase(invoke_func, &Destroy), + functor_(std::forward<ForwardFunctor>(functor)), + bound_args_(std::forward<ForwardBoundArgs>(bound_args)...) { + DCHECK(!IsNull(functor_)); + } + + ~BindState() = default; + + static void Destroy(const BindStateBase* self) { + delete static_cast<const BindState*>(self); + } +}; + +// Used to implement MakeBindStateType. +template <bool is_method, typename Functor, typename... BoundArgs> +struct MakeBindStateTypeImpl; + +template <typename Functor, typename... BoundArgs> +struct MakeBindStateTypeImpl<false, Functor, BoundArgs...> { + static_assert(!HasRefCountedTypeAsRawPtr<std::decay_t<BoundArgs>...>::value, + "A parameter is a refcounted type and needs scoped_refptr."); + using Type = BindState<std::decay_t<Functor>, std::decay_t<BoundArgs>...>; +}; + +template <typename Functor> +struct MakeBindStateTypeImpl<true, Functor> { + using Type = BindState<std::decay_t<Functor>>; +}; + +template <typename Functor, typename Receiver, typename... BoundArgs> +struct MakeBindStateTypeImpl<true, Functor, Receiver, BoundArgs...> { + private: + using DecayedReceiver = std::decay_t<Receiver>; + + static_assert(!std::is_array<std::remove_reference_t<Receiver>>::value, + "First bound argument to a method cannot be an array."); + static_assert( + !std::is_pointer<DecayedReceiver>::value || + IsRefCountedType<std::remove_pointer_t<DecayedReceiver>>::value, + "Receivers may not be raw pointers. If using a raw pointer here is safe" + " and has no lifetime concerns, use base::Unretained() and document why" + " it's safe."); + static_assert(!HasRefCountedTypeAsRawPtr<std::decay_t<BoundArgs>...>::value, + "A parameter is a refcounted type and needs scoped_refptr."); + + public: + using Type = BindState< + std::decay_t<Functor>, + std::conditional_t<std::is_pointer<DecayedReceiver>::value, + scoped_refptr<std::remove_pointer_t<DecayedReceiver>>, + DecayedReceiver>, + std::decay_t<BoundArgs>...>; +}; + +template <typename Functor, typename... BoundArgs> +using MakeBindStateType = + typename MakeBindStateTypeImpl<MakeFunctorTraits<Functor>::is_method, + Functor, + BoundArgs...>::Type; + +} // namespace internal + +// An injection point to control |this| pointer behavior on a method invocation. +// If IsWeakReceiver<> is true_type for |T| and |T| is used for a receiver of a +// method, base::Bind cancels the method invocation if the receiver is tested as +// false. +// E.g. Foo::bar() is not called: +// struct Foo : base::SupportsWeakPtr<Foo> { +// void bar() {} +// }; +// +// WeakPtr<Foo> oo = nullptr; +// base::BindOnce(&Foo::bar, oo).Run(); +template <typename T> +struct IsWeakReceiver : std::false_type {}; + +template <typename T> +struct IsWeakReceiver<std::reference_wrapper<T>> : IsWeakReceiver<T> {}; + +template <typename T> +struct IsWeakReceiver<WeakPtr<T>> : std::true_type {}; + +// An injection point to control how bound objects passed to the target +// function. BindUnwrapTraits<>::Unwrap() is called for each bound objects right +// before the target function is invoked. +template <typename> +struct BindUnwrapTraits { + template <typename T> + static T&& Unwrap(T&& o) { + return std::forward<T>(o); + } +}; + +template <typename T> +struct BindUnwrapTraits<internal::UnretainedWrapper<T>> { + static T* Unwrap(const internal::UnretainedWrapper<T>& o) { return o.get(); } +}; + +template <typename T> +struct BindUnwrapTraits<std::reference_wrapper<T>> { + static T& Unwrap(std::reference_wrapper<T> o) { return o.get(); } +}; + +template <typename T> +struct BindUnwrapTraits<internal::RetainedRefWrapper<T>> { + static T* Unwrap(const internal::RetainedRefWrapper<T>& o) { return o.get(); } +}; + +template <typename T, typename Deleter> +struct BindUnwrapTraits<internal::OwnedWrapper<T, Deleter>> { + static T* Unwrap(const internal::OwnedWrapper<T, Deleter>& o) { + return o.get(); + } +}; + +template <typename T> +struct BindUnwrapTraits<internal::PassedWrapper<T>> { + static T Unwrap(const internal::PassedWrapper<T>& o) { return o.Take(); } +}; + +#if defined(OS_WIN) +template <typename T> +struct BindUnwrapTraits<Microsoft::WRL::ComPtr<T>> { + static T* Unwrap(const Microsoft::WRL::ComPtr<T>& ptr) { return ptr.Get(); } +}; +#endif + +// CallbackCancellationTraits allows customization of Callback's cancellation +// semantics. By default, callbacks are not cancellable. A specialization should +// set is_cancellable = true and implement an IsCancelled() that returns if the +// callback should be cancelled. +template <typename Functor, typename BoundArgsTuple, typename SFINAE> +struct CallbackCancellationTraits { + static constexpr bool is_cancellable = false; +}; + +// Specialization for method bound to weak pointer receiver. +template <typename Functor, typename... BoundArgs> +struct CallbackCancellationTraits< + Functor, + std::tuple<BoundArgs...>, + std::enable_if_t< + internal::IsWeakMethod<internal::FunctorTraits<Functor>::is_method, + BoundArgs...>::value>> { + static constexpr bool is_cancellable = true; + + template <typename Receiver, typename... Args> + static bool IsCancelled(const Functor&, + const Receiver& receiver, + const Args&...) { + return !receiver; + } + + template <typename Receiver, typename... Args> + static bool MaybeValid(const Functor&, + const Receiver& receiver, + const Args&...) { + return receiver.MaybeValid(); + } +}; + +// Specialization for a nested bind. +template <typename Signature, typename... BoundArgs> +struct CallbackCancellationTraits<OnceCallback<Signature>, + std::tuple<BoundArgs...>> { + static constexpr bool is_cancellable = true; + + template <typename Functor> + static bool IsCancelled(const Functor& functor, const BoundArgs&...) { + return functor.IsCancelled(); + } + + template <typename Functor> + static bool MaybeValid(const Functor& functor, const BoundArgs&...) { + return functor.MaybeValid(); + } +}; + +template <typename Signature, typename... BoundArgs> +struct CallbackCancellationTraits<RepeatingCallback<Signature>, + std::tuple<BoundArgs...>> { + static constexpr bool is_cancellable = true; + + template <typename Functor> + static bool IsCancelled(const Functor& functor, const BoundArgs&...) { + return functor.IsCancelled(); + } + + template <typename Functor> + static bool MaybeValid(const Functor& functor, const BoundArgs&...) { + return functor.MaybeValid(); + } +}; + +// Returns a RunType of bound functor. +// E.g. MakeUnboundRunType<R(A, B, C), A, B> is evaluated to R(C). +template <typename Functor, typename... BoundArgs> +using MakeUnboundRunType = + typename internal::BindTypeHelper<Functor, BoundArgs...>::UnboundRunType; + +} // namespace base + +#endif // BASE_BIND_INTERNAL_H_ |