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// Copyright 2021 the V8 project 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 INCLUDE_V8_WEAK_CALLBACK_INFO_H_
#define INCLUDE_V8_WEAK_CALLBACK_INFO_H_
#include <cstring>
#include "cppgc/internal/conditional-stack-allocated.h" // NOLINT(build/include_directory)
#include "v8config.h" // NOLINT(build/include_directory)
namespace v8 {
class Isolate;
namespace api_internal {
V8_EXPORT void InternalFieldOutOfBounds(int index);
} // namespace api_internal
static constexpr int kInternalFieldsInWeakCallback = 2;
static constexpr int kEmbedderFieldsInWeakCallback = 2;
template <typename T>
class WeakCallbackInfo
: public cppgc::internal::ConditionalStackAllocatedBase<T> {
public:
using Callback = void (*)(const WeakCallbackInfo<T>& data);
WeakCallbackInfo(Isolate* isolate, T* parameter,
void* embedder_fields[kEmbedderFieldsInWeakCallback],
Callback* callback)
: isolate_(isolate), parameter_(parameter), callback_(callback) {
memcpy(embedder_fields_, embedder_fields,
sizeof(embedder_fields[0]) * kEmbedderFieldsInWeakCallback);
}
V8_INLINE Isolate* GetIsolate() const { return isolate_; }
V8_INLINE T* GetParameter() const { return parameter_; }
V8_INLINE void* GetInternalField(int index) const;
/**
* When a weak callback is first invoked the embedders _must_ Reset() the
* handle which triggered the callback. The handle itself is unusable for
* anything else. No other V8 API calls may be called in the first callback.
* Additional work requires scheduling a second invocation via
* `SetSecondPassCallback()` which will be called some time after all the
* initial callbacks are processed.
*
* The second pass callback is prohibited from executing JavaScript. Embedders
* should schedule another callback in case this is required.
*/
void SetSecondPassCallback(Callback callback) const { *callback_ = callback; }
private:
Isolate* isolate_;
T* parameter_;
Callback* callback_;
void* embedder_fields_[kEmbedderFieldsInWeakCallback];
};
/**
* Weakness type for weak handles.
*/
enum class WeakCallbackType {
/**
* Passes a user-defined void* parameter back to the callback.
*/
kParameter,
/**
* Passes the first two internal fields of the object back to the callback.
*/
kInternalFields,
};
template <class T>
void* WeakCallbackInfo<T>::GetInternalField(int index) const {
#ifdef V8_ENABLE_CHECKS
if (index < 0 || index >= kEmbedderFieldsInWeakCallback) {
api_internal::InternalFieldOutOfBounds(index);
}
#endif
return embedder_fields_[index];
}
} // namespace v8
#endif // INCLUDE_V8_WEAK_CALLBACK_INFO_H_
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