Import Cobalt 19.master.0.205881
diff --git a/src/base/callback_internal.h b/src/base/callback_internal.h
index 2f834c3..a9215fc 100644
--- a/src/base/callback_internal.h
+++ b/src/base/callback_internal.h
@@ -8,55 +8,152 @@
#ifndef BASE_CALLBACK_INTERNAL_H_
#define BASE_CALLBACK_INTERNAL_H_
-#include <stddef.h>
-
#include "base/base_export.h"
+#include "base/callback_forward.h"
+#include "base/macros.h"
#include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
-
-template <typename T>
-class ScopedVector;
namespace base {
+
+struct FakeBindState;
+
namespace internal {
+class CallbackBase;
+class CallbackBaseCopyable;
+
+class BindStateBase;
+
+template <typename Functor, typename... BoundArgs>
+struct BindState;
+
+struct BindStateBaseRefCountTraits {
+ static void Destruct(const BindStateBase*);
+};
+
+template <typename T>
+#if defined(STARBOARD) && defined(SB_IS_COMPILER_MSVC)
+// On MSVC, std::conditional_t does not return true with some equal types.
+using PassingType = T&&;
+#else
+using PassingType = std::conditional_t<std::is_scalar<T>::value, T, T&&>;
+#endif
+
// BindStateBase is used to provide an opaque handle that the Callback
// class can use to represent a function object with bound arguments. It
// behaves as an existential type that is used by a corresponding
// DoInvoke function to perform the function execution. This allows
// us to shield the Callback class from the types of the bound argument via
// "type erasure."
-class BindStateBase : public RefCountedThreadSafe<BindStateBase> {
- protected:
- friend class RefCountedThreadSafe<BindStateBase>;
- virtual ~BindStateBase() {}
+// At the base level, the only task is to add reference counting data. Don't use
+// RefCountedThreadSafe since it requires the destructor to be a virtual method.
+// Creating a vtable for every BindState template instantiation results in a lot
+// of bloat. Its only task is to call the destructor which can be done with a
+// function pointer.
+class BASE_EXPORT BindStateBase
+ : public RefCountedThreadSafe<BindStateBase, BindStateBaseRefCountTraits> {
+ public:
+ REQUIRE_ADOPTION_FOR_REFCOUNTED_TYPE();
+
+ enum CancellationQueryMode {
+ IS_CANCELLED,
+ MAYBE_VALID,
+ };
+
+ using InvokeFuncStorage = void(*)();
+
+ private:
+ BindStateBase(InvokeFuncStorage polymorphic_invoke,
+ void (*destructor)(const BindStateBase*));
+ BindStateBase(InvokeFuncStorage polymorphic_invoke,
+ void (*destructor)(const BindStateBase*),
+ bool (*query_cancellation_traits)(const BindStateBase*,
+ CancellationQueryMode mode));
+
+ ~BindStateBase() = default;
+
+ friend struct BindStateBaseRefCountTraits;
+ friend class RefCountedThreadSafe<BindStateBase, BindStateBaseRefCountTraits>;
+
+ friend class CallbackBase;
+ friend class CallbackBaseCopyable;
+
+ // Whitelist subclasses that access the destructor of BindStateBase.
+ template <typename Functor, typename... BoundArgs>
+ friend struct BindState;
+ friend struct ::base::FakeBindState;
+
+ bool IsCancelled() const {
+ return query_cancellation_traits_(this, IS_CANCELLED);
+ }
+
+ bool MaybeValid() const {
+ return query_cancellation_traits_(this, MAYBE_VALID);
+ }
+
+ // In C++, it is safe to cast function pointers to function pointers of
+ // another type. It is not okay to use void*. We create a InvokeFuncStorage
+ // that that can store our function pointer, and then cast it back to
+ // the original type on usage.
+ InvokeFuncStorage polymorphic_invoke_;
+
+ // Pointer to a function that will properly destroy |this|.
+ void (*destructor_)(const BindStateBase*);
+ bool (*query_cancellation_traits_)(const BindStateBase*,
+ CancellationQueryMode mode);
+
+ DISALLOW_COPY_AND_ASSIGN(BindStateBase);
};
// Holds the Callback methods that don't require specialization to reduce
// template bloat.
+// CallbackBase<MoveOnly> is a direct base class of MoveOnly callbacks, and
+// CallbackBase<Copyable> uses CallbackBase<MoveOnly> for its implementation.
class BASE_EXPORT CallbackBase {
public:
+ inline CallbackBase(CallbackBase&& c) noexcept;
+ CallbackBase& operator=(CallbackBase&& c) noexcept;
+
+ explicit CallbackBase(const CallbackBaseCopyable& c);
+ CallbackBase& operator=(const CallbackBaseCopyable& c);
+
+ explicit CallbackBase(CallbackBaseCopyable&& c) noexcept;
+ CallbackBase& operator=(CallbackBaseCopyable&& c) noexcept;
+
// Returns true if Callback is null (doesn't refer to anything).
- bool is_null() const;
+ bool is_null() const { return !bind_state_; }
+ explicit operator bool() const { return !is_null(); }
+
+ // Returns true if the callback invocation will be nop due to an cancellation.
+ // It's invalid to call this on uninitialized callback.
+ //
+ // Must be called on the Callback's destination sequence.
+ bool IsCancelled() const;
+
+ // If this returns false, the callback invocation will be a nop due to a
+ // cancellation. This may(!) still return true, even on a cancelled callback.
+ //
+ // This function is thread-safe.
+ bool MaybeValid() const;
// Returns the Callback into an uninitialized state.
void Reset();
protected:
- // In C++, it is safe to cast function pointers to function pointers of
- // another type. It is not okay to use void*. We create a InvokeFuncStorage
- // that that can store our function pointer, and then cast it back to
- // the original type on usage.
- typedef void(*InvokeFuncStorage)(void);
+ using InvokeFuncStorage = BindStateBase::InvokeFuncStorage;
// Returns true if this callback equals |other|. |other| may be null.
- bool Equals(const CallbackBase& other) const;
+ bool EqualsInternal(const CallbackBase& other) const;
+
+ constexpr inline CallbackBase();
// Allow initializing of |bind_state_| via the constructor to avoid default
- // initialization of the scoped_refptr. We do not also initialize
- // |polymorphic_invoke_| here because doing a normal assignment in the
- // derived Callback templates makes for much nicer compiler errors.
- explicit CallbackBase(BindStateBase* bind_state);
+ // initialization of the scoped_refptr.
+ explicit inline CallbackBase(BindStateBase* bind_state);
+
+ InvokeFuncStorage polymorphic_invoke() const {
+ return bind_state_->polymorphic_invoke_;
+ }
// Force the destructor to be instantiated inside this translation unit so
// that our subclasses will not get inlined versions. Avoids more template
@@ -64,129 +161,28 @@
~CallbackBase();
scoped_refptr<BindStateBase> bind_state_;
- InvokeFuncStorage polymorphic_invoke_;
};
-// This is a typetraits object that's used to take an argument type, and
-// extract a suitable type for storing and forwarding arguments.
-//
-// In particular, it strips off references, and converts arrays to
-// pointers for storage; and it avoids accidentally trying to create a
-// "reference of a reference" if the argument is a reference type.
-//
-// This array type becomes an issue for storage because we are passing bound
-// parameters by const reference. In this case, we end up passing an actual
-// array type in the initializer list which C++ does not allow. This will
-// break passing of C-string literals.
-template <typename T>
-struct CallbackParamTraits {
- typedef const T& ForwardType;
- typedef T StorageType;
+constexpr CallbackBase::CallbackBase() = default;
+CallbackBase::CallbackBase(CallbackBase&&) noexcept = default;
+CallbackBase::CallbackBase(BindStateBase* bind_state)
+ : bind_state_(AdoptRef(bind_state)) {}
+
+// CallbackBase<Copyable> is a direct base class of Copyable Callbacks.
+class BASE_EXPORT CallbackBaseCopyable : public CallbackBase {
+ public:
+ CallbackBaseCopyable(const CallbackBaseCopyable& c);
+ CallbackBaseCopyable(CallbackBaseCopyable&& c) noexcept = default;
+ CallbackBaseCopyable& operator=(const CallbackBaseCopyable& c);
+ CallbackBaseCopyable& operator=(CallbackBaseCopyable&& c) noexcept;
+
+ protected:
+ constexpr CallbackBaseCopyable() = default;
+ explicit CallbackBaseCopyable(BindStateBase* bind_state)
+ : CallbackBase(bind_state) {}
+ ~CallbackBaseCopyable() = default;
};
-// The Storage should almost be impossible to trigger unless someone manually
-// specifies type of the bind parameters. However, in case they do,
-// this will guard against us accidentally storing a reference parameter.
-//
-// The ForwardType should only be used for unbound arguments.
-template <typename T>
-struct CallbackParamTraits<T&> {
- typedef T& ForwardType;
- typedef T StorageType;
-};
-
-// Note that for array types, we implicitly add a const in the conversion. This
-// means that it is not possible to bind array arguments to functions that take
-// a non-const pointer. Trying to specialize the template based on a "const
-// T[n]" does not seem to match correctly, so we are stuck with this
-// restriction.
-template <typename T, size_t n>
-struct CallbackParamTraits<T[n]> {
- typedef const T* ForwardType;
- typedef const T* StorageType;
-};
-
-// See comment for CallbackParamTraits<T[n]>.
-template <typename T>
-struct CallbackParamTraits<T[]> {
- typedef const T* ForwardType;
- typedef const T* StorageType;
-};
-
-// Parameter traits for movable-but-not-copyable scopers.
-//
-// Callback<>/Bind() understands movable-but-not-copyable semantics where
-// the type cannot be copied but can still have its state destructively
-// transferred (aka. moved) to another instance of the same type by calling a
-// helper function. When used with Bind(), this signifies transferal of the
-// object's state to the target function.
-//
-// For these types, the ForwardType must not be a const reference, or a
-// reference. A const reference is inappropriate, and would break const
-// correctness, because we are implementing a destructive move. A non-const
-// reference cannot be used with temporaries which means the result of a
-// function or a cast would not be usable with Callback<> or Bind().
-//
-// TODO(ajwong): We might be able to use SFINAE to search for the existence of
-// a Pass() function in the type and avoid the whitelist in CallbackParamTraits
-// and CallbackForward.
-template <typename T>
-struct CallbackParamTraits<scoped_ptr<T> > {
- typedef scoped_ptr<T> ForwardType;
- typedef scoped_ptr<T> StorageType;
-};
-
-template <typename T>
-struct CallbackParamTraits<scoped_array<T> > {
- typedef scoped_array<T> ForwardType;
- typedef scoped_array<T> StorageType;
-};
-
-template <typename T, typename R>
-struct CallbackParamTraits<scoped_ptr_malloc<T, R> > {
- typedef scoped_ptr_malloc<T, R> ForwardType;
- typedef scoped_ptr_malloc<T, R> StorageType;
-};
-
-template <typename T>
-struct CallbackParamTraits<ScopedVector<T> > {
- typedef ScopedVector<T> ForwardType;
- typedef ScopedVector<T> StorageType;
-};
-
-// CallbackForward() is a very limited simulation of C++11's std::forward()
-// used by the Callback/Bind system for a set of movable-but-not-copyable
-// types. It is needed because forwarding a movable-but-not-copyable
-// argument to another function requires us to invoke the proper move
-// operator to create a rvalue version of the type. The supported types are
-// whitelisted below as overloads of the CallbackForward() function. The
-// default template compiles out to be a no-op.
-//
-// In C++11, std::forward would replace all uses of this function. However, it
-// is impossible to implement a general std::forward with C++11 due to a lack
-// of rvalue references.
-//
-// In addition to Callback/Bind, this is used by PostTaskAndReplyWithResult to
-// simulate std::forward() and forward the result of one Callback as a
-// parameter to another callback. This is to support Callbacks that return
-// the movable-but-not-copyable types whitelisted above.
-template <typename T>
-T& CallbackForward(T& t) { return t; }
-
-template <typename T>
-scoped_ptr<T> CallbackForward(scoped_ptr<T>& p) { return p.Pass(); }
-
-template <typename T>
-scoped_array<T> CallbackForward(scoped_array<T>& p) { return p.Pass(); }
-
-template <typename T, typename R>
-scoped_ptr_malloc<T, R> CallbackForward(scoped_ptr_malloc<T, R>& p) {
- return p.Pass();
-}
-
-template <typename T>
-ScopedVector<T> CallbackForward(ScopedVector<T>& p) { return p.Pass(); }
-
} // namespace internal
} // namespace base
