cef/include/base/internal/cef_callback_internal.h

276 lines
10 KiB
C++

// Copyright (c) 2012 Google Inc. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * 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.
// * Neither the name of Google Inc. nor the name Chromium Embedded
// Framework nor the names of its contributors may be used to endorse
// or promote products derived from this software without specific prior
// written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
// OWNER OR 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.
// Do not include this header file directly. Use base/cef_bind.h or
// base/cef_callback.h instead.
// This file contains utility functions and classes that help the
// implementation, and management of the Callback objects.
#ifndef CEF_INCLUDE_BASE_INTERNAL_CEF_CALLBACK_INTERNAL_H_
#define CEF_INCLUDE_BASE_INTERNAL_CEF_CALLBACK_INTERNAL_H_
#include "include/base/cef_callback_forward.h"
#include "include/base/cef_ref_counted.h"
namespace base {
struct FakeBindState;
namespace cef_internal {
class BindStateBase;
class FinallyExecutorCommon;
class ThenAndCatchExecutorCommon;
template <typename ReturnType>
class PostTaskExecutor;
template <typename Functor, typename... BoundArgs>
struct BindState;
class CallbackBase;
class CallbackBaseCopyable;
struct BindStateBaseRefCountTraits {
static void Destruct(const BindStateBase*);
};
template <typename T>
using PassingType = std::conditional_t<std::is_scalar<T>::value, T, T&&>;
// 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."
// At the base level, the only task is to add reference counting data. Avoid
// using or inheriting any virtual functions. 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 BindStateBase
: public RefCountedThreadSafe<BindStateBase, BindStateBaseRefCountTraits> {
public:
REQUIRE_ADOPTION_FOR_REFCOUNTED_TYPE();
enum CancellationQueryMode {
IS_CANCELLED,
MAYBE_VALID,
};
using InvokeFuncStorage = void (*)();
BindStateBase(const BindStateBase&) = delete;
BindStateBase& operator=(const BindStateBase&) = delete;
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;
// Allowlist 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);
};
// 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 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 { 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:
friend class FinallyExecutorCommon;
friend class ThenAndCatchExecutorCommon;
template <typename ReturnType>
friend class PostTaskExecutor;
using InvokeFuncStorage = BindStateBase::InvokeFuncStorage;
// Returns true if this callback equals |other|. |other| may be null.
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.
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
// bloat.
~CallbackBase();
scoped_refptr<BindStateBase> bind_state_;
};
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 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;
};
// Helpers for the `Then()` implementation.
template <typename OriginalCallback, typename ThenCallback>
struct ThenHelper;
// Specialization when original callback returns `void`.
template <template <typename> class OriginalCallback,
template <typename>
class ThenCallback,
typename... OriginalArgs,
typename ThenR,
typename... ThenArgs>
struct ThenHelper<OriginalCallback<void(OriginalArgs...)>,
ThenCallback<ThenR(ThenArgs...)>> {
static_assert(sizeof...(ThenArgs) == 0,
"|then| callback cannot accept parameters if |this| has a "
"void return type.");
static auto CreateTrampoline() {
return [](OriginalCallback<void(OriginalArgs...)> c1,
ThenCallback<ThenR(ThenArgs...)> c2, OriginalArgs... c1_args) {
std::move(c1).Run(std::forward<OriginalArgs>(c1_args)...);
return std::move(c2).Run();
};
}
};
// Specialization when original callback returns a non-void type.
template <template <typename> class OriginalCallback,
template <typename>
class ThenCallback,
typename OriginalR,
typename... OriginalArgs,
typename ThenR,
typename... ThenArgs>
struct ThenHelper<OriginalCallback<OriginalR(OriginalArgs...)>,
ThenCallback<ThenR(ThenArgs...)>> {
static_assert(sizeof...(ThenArgs) == 1,
"|then| callback must accept exactly one parameter if |this| "
"has a non-void return type.");
// TODO(dcheng): This should probably check is_convertible as well (same with
// `AssertBindArgsValidity`).
static_assert(std::is_constructible<ThenArgs..., OriginalR&&>::value,
"|then| callback's parameter must be constructible from "
"return type of |this|.");
static auto CreateTrampoline() {
return [](OriginalCallback<OriginalR(OriginalArgs...)> c1,
ThenCallback<ThenR(ThenArgs...)> c2, OriginalArgs... c1_args) {
return std::move(c2).Run(
std::move(c1).Run(std::forward<OriginalArgs>(c1_args)...));
};
}
};
} // namespace cef_internal
} // namespace base
#endif // CEF_INCLUDE_BASE_INTERNAL_CEF_CALLBACK_INTERNAL_H_