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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 17:32:43 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 17:32:43 +0000
commit6bf0a5cb5034a7e684dcc3500e841785237ce2dd (patch)
treea68f146d7fa01f0134297619fbe7e33db084e0aa /security/sandbox/chromium/base/bind.h
parentInitial commit. (diff)
downloadthunderbird-6bf0a5cb5034a7e684dcc3500e841785237ce2dd.tar.xz
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Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+// 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_H_
+#define BASE_BIND_H_
+
+#include <functional>
+#include <memory>
+#include <type_traits>
+#include <utility>
+
+#include "base/bind_internal.h"
+#include "base/compiler_specific.h"
+#include "build/build_config.h"
+
+#if defined(OS_MACOSX) && !HAS_FEATURE(objc_arc)
+#include "base/mac/scoped_block.h"
+#endif
+
+// -----------------------------------------------------------------------------
+// Usage documentation
+// -----------------------------------------------------------------------------
+//
+// Overview:
+// base::BindOnce() and base::BindRepeating() are helpers for creating
+// base::OnceCallback and base::RepeatingCallback objects respectively.
+//
+// For a runnable object of n-arity, the base::Bind*() family allows partial
+// application of the first m arguments. The remaining n - m arguments must be
+// passed when invoking the callback with Run().
+//
+// // The first argument is bound at callback creation; the remaining
+// // two must be passed when calling Run() on the callback object.
+// base::OnceCallback<long(int, long)> cb = base::BindOnce(
+// [](short x, int y, long z) { return x * y * z; }, 42);
+//
+// When binding to a method, the receiver object must also be specified at
+// callback creation time. When Run() is invoked, the method will be invoked on
+// the specified receiver object.
+//
+// class C : public base::RefCounted<C> { void F(); };
+// auto instance = base::MakeRefCounted<C>();
+// auto cb = base::BindOnce(&C::F, instance);
+// std::move(cb).Run(); // Identical to instance->F()
+//
+// base::Bind is currently a type alias for base::BindRepeating(). In the
+// future, we expect to flip this to default to base::BindOnce().
+//
+// See //docs/callback.md for the full documentation.
+//
+// -----------------------------------------------------------------------------
+// Implementation notes
+// -----------------------------------------------------------------------------
+//
+// If you're reading the implementation, before proceeding further, you should
+// read the top comment of base/bind_internal.h for a definition of common
+// terms and concepts.
+
+namespace base {
+
+namespace internal {
+
+// IsOnceCallback<T> is a std::true_type if |T| is a OnceCallback.
+template <typename T>
+struct IsOnceCallback : std::false_type {};
+
+template <typename Signature>
+struct IsOnceCallback<OnceCallback<Signature>> : std::true_type {};
+
+// Helper to assert that parameter |i| of type |Arg| can be bound, which means:
+// - |Arg| can be retained internally as |Storage|.
+// - |Arg| can be forwarded as |Unwrapped| to |Param|.
+template <size_t i,
+ typename Arg,
+ typename Storage,
+ typename Unwrapped,
+ typename Param>
+struct AssertConstructible {
+ private:
+ static constexpr bool param_is_forwardable =
+ std::is_constructible<Param, Unwrapped>::value;
+ // Unlike the check for binding into storage below, the check for
+ // forwardability drops the const qualifier for repeating callbacks. This is
+ // to try to catch instances where std::move()--which forwards as a const
+ // reference with repeating callbacks--is used instead of base::Passed().
+ static_assert(
+ param_is_forwardable ||
+ !std::is_constructible<Param, std::decay_t<Unwrapped>&&>::value,
+ "Bound argument |i| is move-only but will be forwarded by copy. "
+ "Ensure |Arg| is bound using base::Passed(), not std::move().");
+ static_assert(
+ param_is_forwardable,
+ "Bound argument |i| of type |Arg| cannot be forwarded as "
+ "|Unwrapped| to the bound functor, which declares it as |Param|.");
+
+ static constexpr bool arg_is_storable =
+ std::is_constructible<Storage, Arg>::value;
+ static_assert(arg_is_storable ||
+ !std::is_constructible<Storage, std::decay_t<Arg>&&>::value,
+ "Bound argument |i| is move-only but will be bound by copy. "
+ "Ensure |Arg| is mutable and bound using std::move().");
+ static_assert(arg_is_storable,
+ "Bound argument |i| of type |Arg| cannot be converted and "
+ "bound as |Storage|.");
+};
+
+// Takes three same-length TypeLists, and applies AssertConstructible for each
+// triples.
+template <typename Index,
+ typename Args,
+ typename UnwrappedTypeList,
+ typename ParamsList>
+struct AssertBindArgsValidity;
+
+template <size_t... Ns,
+ typename... Args,
+ typename... Unwrapped,
+ typename... Params>
+struct AssertBindArgsValidity<std::index_sequence<Ns...>,
+ TypeList<Args...>,
+ TypeList<Unwrapped...>,
+ TypeList<Params...>>
+ : AssertConstructible<Ns, Args, std::decay_t<Args>, Unwrapped, Params>... {
+ static constexpr bool ok = true;
+};
+
+// The implementation of TransformToUnwrappedType below.
+template <bool is_once, typename T>
+struct TransformToUnwrappedTypeImpl;
+
+template <typename T>
+struct TransformToUnwrappedTypeImpl<true, T> {
+ using StoredType = std::decay_t<T>;
+ using ForwardType = StoredType&&;
+ using Unwrapped = decltype(Unwrap(std::declval<ForwardType>()));
+};
+
+template <typename T>
+struct TransformToUnwrappedTypeImpl<false, T> {
+ using StoredType = std::decay_t<T>;
+ using ForwardType = const StoredType&;
+ using Unwrapped = decltype(Unwrap(std::declval<ForwardType>()));
+};
+
+// Transform |T| into `Unwrapped` type, which is passed to the target function.
+// Example:
+// In is_once == true case,
+// `int&&` -> `int&&`,
+// `const int&` -> `int&&`,
+// `OwnedWrapper<int>&` -> `int*&&`.
+// In is_once == false case,
+// `int&&` -> `const int&`,
+// `const int&` -> `const int&`,
+// `OwnedWrapper<int>&` -> `int* const &`.
+template <bool is_once, typename T>
+using TransformToUnwrappedType =
+ typename TransformToUnwrappedTypeImpl<is_once, T>::Unwrapped;
+
+// Transforms |Args| into `Unwrapped` types, and packs them into a TypeList.
+// If |is_method| is true, tries to dereference the first argument to support
+// smart pointers.
+template <bool is_once, bool is_method, typename... Args>
+struct MakeUnwrappedTypeListImpl {
+ using Type = TypeList<TransformToUnwrappedType<is_once, Args>...>;
+};
+
+// Performs special handling for this pointers.
+// Example:
+// int* -> int*,
+// std::unique_ptr<int> -> int*.
+template <bool is_once, typename Receiver, typename... Args>
+struct MakeUnwrappedTypeListImpl<is_once, true, Receiver, Args...> {
+ using UnwrappedReceiver = TransformToUnwrappedType<is_once, Receiver>;
+ using Type = TypeList<decltype(&*std::declval<UnwrappedReceiver>()),
+ TransformToUnwrappedType<is_once, Args>...>;
+};
+
+template <bool is_once, bool is_method, typename... Args>
+using MakeUnwrappedTypeList =
+ typename MakeUnwrappedTypeListImpl<is_once, is_method, Args...>::Type;
+
+// Used below in BindImpl to determine whether to use Invoker::Run or
+// Invoker::RunOnce.
+// Note: Simply using `kIsOnce ? &Invoker::RunOnce : &Invoker::Run` does not
+// work, since the compiler needs to check whether both expressions are
+// well-formed. Using `Invoker::Run` with a OnceCallback triggers a
+// static_assert, which is why the ternary expression does not compile.
+// TODO(crbug.com/752720): Remove this indirection once we have `if constexpr`.
+template <typename Invoker>
+constexpr auto GetInvokeFunc(std::true_type) {
+ return Invoker::RunOnce;
+}
+
+template <typename Invoker>
+constexpr auto GetInvokeFunc(std::false_type) {
+ return Invoker::Run;
+}
+
+template <template <typename> class CallbackT,
+ typename Functor,
+ typename... Args>
+decltype(auto) BindImpl(Functor&& functor, Args&&... args) {
+ // This block checks if each |args| matches to the corresponding params of the
+ // target function. This check does not affect the behavior of Bind, but its
+ // error message should be more readable.
+ static constexpr bool kIsOnce = IsOnceCallback<CallbackT<void()>>::value;
+ using Helper = internal::BindTypeHelper<Functor, Args...>;
+ using FunctorTraits = typename Helper::FunctorTraits;
+ using BoundArgsList = typename Helper::BoundArgsList;
+ using UnwrappedArgsList =
+ internal::MakeUnwrappedTypeList<kIsOnce, FunctorTraits::is_method,
+ Args&&...>;
+ using BoundParamsList = typename Helper::BoundParamsList;
+ static_assert(internal::AssertBindArgsValidity<
+ std::make_index_sequence<Helper::num_bounds>, BoundArgsList,
+ UnwrappedArgsList, BoundParamsList>::ok,
+ "The bound args need to be convertible to the target params.");
+
+ using BindState = internal::MakeBindStateType<Functor, Args...>;
+ using UnboundRunType = MakeUnboundRunType<Functor, Args...>;
+ using Invoker = internal::Invoker<BindState, UnboundRunType>;
+ using CallbackType = CallbackT<UnboundRunType>;
+
+ // Store the invoke func into PolymorphicInvoke before casting it to
+ // InvokeFuncStorage, so that we can ensure its type matches to
+ // PolymorphicInvoke, to which CallbackType will cast back.
+ using PolymorphicInvoke = typename CallbackType::PolymorphicInvoke;
+ PolymorphicInvoke invoke_func =
+ GetInvokeFunc<Invoker>(std::integral_constant<bool, kIsOnce>());
+
+ using InvokeFuncStorage = internal::BindStateBase::InvokeFuncStorage;
+ return CallbackType(BindState::Create(
+ reinterpret_cast<InvokeFuncStorage>(invoke_func),
+ std::forward<Functor>(functor), std::forward<Args>(args)...));
+}
+
+} // namespace internal
+
+// Bind as OnceCallback.
+template <typename Functor, typename... Args>
+inline OnceCallback<MakeUnboundRunType<Functor, Args...>> BindOnce(
+ Functor&& functor,
+ Args&&... args) {
+ static_assert(!internal::IsOnceCallback<std::decay_t<Functor>>() ||
+ (std::is_rvalue_reference<Functor&&>() &&
+ !std::is_const<std::remove_reference_t<Functor>>()),
+ "BindOnce requires non-const rvalue for OnceCallback binding."
+ " I.e.: base::BindOnce(std::move(callback)).");
+
+ return internal::BindImpl<OnceCallback>(std::forward<Functor>(functor),
+ std::forward<Args>(args)...);
+}
+
+// Bind as RepeatingCallback.
+template <typename Functor, typename... Args>
+inline RepeatingCallback<MakeUnboundRunType<Functor, Args...>>
+BindRepeating(Functor&& functor, Args&&... args) {
+ static_assert(
+ !internal::IsOnceCallback<std::decay_t<Functor>>(),
+ "BindRepeating cannot bind OnceCallback. Use BindOnce with std::move().");
+
+ return internal::BindImpl<RepeatingCallback>(std::forward<Functor>(functor),
+ std::forward<Args>(args)...);
+}
+
+// Unannotated Bind.
+// TODO(tzik): Deprecate this and migrate to OnceCallback and
+// RepeatingCallback, once they get ready.
+template <typename Functor, typename... Args>
+inline Callback<MakeUnboundRunType<Functor, Args...>>
+Bind(Functor&& functor, Args&&... args) {
+ return base::BindRepeating(std::forward<Functor>(functor),
+ std::forward<Args>(args)...);
+}
+
+// Special cases for binding to a base::Callback without extra bound arguments.
+template <typename Signature>
+OnceCallback<Signature> BindOnce(OnceCallback<Signature> callback) {
+ return callback;
+}
+
+template <typename Signature>
+OnceCallback<Signature> BindOnce(RepeatingCallback<Signature> callback) {
+ return callback;
+}
+
+template <typename Signature>
+RepeatingCallback<Signature> BindRepeating(
+ RepeatingCallback<Signature> callback) {
+ return callback;
+}
+
+template <typename Signature>
+Callback<Signature> Bind(Callback<Signature> callback) {
+ return callback;
+}
+
+// Unretained() allows binding a non-refcounted class, and to disable
+// refcounting on arguments that are refcounted objects.
+//
+// EXAMPLE OF Unretained():
+//
+// class Foo {
+// public:
+// void func() { cout << "Foo:f" << endl; }
+// };
+//
+// // In some function somewhere.
+// Foo foo;
+// OnceClosure foo_callback =
+// BindOnce(&Foo::func, Unretained(&foo));
+// std::move(foo_callback).Run(); // Prints "Foo:f".
+//
+// Without the Unretained() wrapper on |&foo|, the above call would fail
+// to compile because Foo does not support the AddRef() and Release() methods.
+template <typename T>
+static inline internal::UnretainedWrapper<T> Unretained(T* o) {
+ return internal::UnretainedWrapper<T>(o);
+}
+
+// RetainedRef() accepts a ref counted object and retains a reference to it.
+// When the callback is called, the object is passed as a raw pointer.
+//
+// EXAMPLE OF RetainedRef():
+//
+// void foo(RefCountedBytes* bytes) {}
+//
+// scoped_refptr<RefCountedBytes> bytes = ...;
+// OnceClosure callback = BindOnce(&foo, base::RetainedRef(bytes));
+// std::move(callback).Run();
+//
+// Without RetainedRef, the scoped_refptr would try to implicitly convert to
+// a raw pointer and fail compilation:
+//
+// OnceClosure callback = BindOnce(&foo, bytes); // ERROR!
+template <typename T>
+static inline internal::RetainedRefWrapper<T> RetainedRef(T* o) {
+ return internal::RetainedRefWrapper<T>(o);
+}
+template <typename T>
+static inline internal::RetainedRefWrapper<T> RetainedRef(scoped_refptr<T> o) {
+ return internal::RetainedRefWrapper<T>(std::move(o));
+}
+
+// Owned() transfers ownership of an object to the callback resulting from
+// bind; the object will be deleted when the callback is deleted.
+//
+// EXAMPLE OF Owned():
+//
+// void foo(int* arg) { cout << *arg << endl }
+//
+// int* pn = new int(1);
+// RepeatingClosure foo_callback = BindRepeating(&foo, Owned(pn));
+//
+// foo_callback.Run(); // Prints "1"
+// foo_callback.Run(); // Prints "1"
+// *pn = 2;
+// foo_callback.Run(); // Prints "2"
+//
+// foo_callback.Reset(); // |pn| is deleted. Also will happen when
+// // |foo_callback| goes out of scope.
+//
+// Without Owned(), someone would have to know to delete |pn| when the last
+// reference to the callback is deleted.
+template <typename T>
+static inline internal::OwnedWrapper<T> Owned(T* o) {
+ return internal::OwnedWrapper<T>(o);
+}
+
+template <typename T, typename Deleter>
+static inline internal::OwnedWrapper<T, Deleter> Owned(
+ std::unique_ptr<T, Deleter>&& ptr) {
+ return internal::OwnedWrapper<T, Deleter>(std::move(ptr));
+}
+
+// Passed() is for transferring movable-but-not-copyable types (eg. unique_ptr)
+// through a RepeatingCallback. Logically, this signifies a destructive transfer
+// of the state of the argument into the target function. Invoking
+// RepeatingCallback::Run() twice on a callback that was created with a Passed()
+// argument will CHECK() because the first invocation would have already
+// transferred ownership to the target function.
+//
+// Note that Passed() is not necessary with BindOnce(), as std::move() does the
+// same thing. Avoid Passed() in favor of std::move() with BindOnce().
+//
+// EXAMPLE OF Passed():
+//
+// void TakesOwnership(std::unique_ptr<Foo> arg) { }
+// std::unique_ptr<Foo> CreateFoo() { return std::make_unique<Foo>();
+// }
+//
+// auto f = std::make_unique<Foo>();
+//
+// // |cb| is given ownership of Foo(). |f| is now NULL.
+// // You can use std::move(f) in place of &f, but it's more verbose.
+// RepeatingClosure cb = BindRepeating(&TakesOwnership, Passed(&f));
+//
+// // Run was never called so |cb| still owns Foo() and deletes
+// // it on Reset().
+// cb.Reset();
+//
+// // |cb| is given a new Foo created by CreateFoo().
+// cb = BindRepeating(&TakesOwnership, Passed(CreateFoo()));
+//
+// // |arg| in TakesOwnership() is given ownership of Foo(). |cb|
+// // no longer owns Foo() and, if reset, would not delete Foo().
+// cb.Run(); // Foo() is now transferred to |arg| and deleted.
+// cb.Run(); // This CHECK()s since Foo() already been used once.
+//
+// We offer 2 syntaxes for calling Passed(). The first takes an rvalue and is
+// best suited for use with the return value of a function or other temporary
+// rvalues. The second takes a pointer to the scoper and is just syntactic sugar
+// to avoid having to write Passed(std::move(scoper)).
+//
+// Both versions of Passed() prevent T from being an lvalue reference. The first
+// via use of enable_if, and the second takes a T* which will not bind to T&.
+template <typename T,
+ std::enable_if_t<!std::is_lvalue_reference<T>::value>* = nullptr>
+static inline internal::PassedWrapper<T> Passed(T&& scoper) {
+ return internal::PassedWrapper<T>(std::move(scoper));
+}
+template <typename T>
+static inline internal::PassedWrapper<T> Passed(T* scoper) {
+ return internal::PassedWrapper<T>(std::move(*scoper));
+}
+
+// IgnoreResult() is used to adapt a function or callback with a return type to
+// one with a void return. This is most useful if you have a function with,
+// say, a pesky ignorable bool return that you want to use with PostTask or
+// something else that expect a callback with a void return.
+//
+// EXAMPLE OF IgnoreResult():
+//
+// int DoSomething(int arg) { cout << arg << endl; }
+//
+// // Assign to a callback with a void return type.
+// OnceCallback<void(int)> cb = BindOnce(IgnoreResult(&DoSomething));
+// std::move(cb).Run(1); // Prints "1".
+//
+// // Prints "2" on |ml|.
+// ml->PostTask(FROM_HERE, BindOnce(IgnoreResult(&DoSomething), 2);
+template <typename T>
+static inline internal::IgnoreResultHelper<T> IgnoreResult(T data) {
+ return internal::IgnoreResultHelper<T>(std::move(data));
+}
+
+#if defined(OS_MACOSX) && !HAS_FEATURE(objc_arc)
+
+// RetainBlock() is used to adapt an Objective-C block when Automated Reference
+// Counting (ARC) is disabled. This is unnecessary when ARC is enabled, as the
+// BindOnce and BindRepeating already support blocks then.
+//
+// EXAMPLE OF RetainBlock():
+//
+// // Wrap the block and bind it to a callback.
+// OnceCallback<void(int)> cb =
+// BindOnce(RetainBlock(^(int n) { NSLog(@"%d", n); }));
+// std::move(cb).Run(1); // Logs "1".
+template <typename R, typename... Args>
+base::mac::ScopedBlock<R (^)(Args...)> RetainBlock(R (^block)(Args...)) {
+ return base::mac::ScopedBlock<R (^)(Args...)>(block,
+ base::scoped_policy::RETAIN);
+}
+
+#endif // defined(OS_MACOSX) && !HAS_FEATURE(objc_arc)
+
+} // namespace base
+
+#endif // BASE_BIND_H_