// 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_SNAPSHOT_H_
#define INCLUDE_V8_SNAPSHOT_H_
#include "v8-internal.h" // NOLINT(build/include_directory)
#include "v8-local-handle.h" // NOLINT(build/include_directory)
#include "v8config.h" // NOLINT(build/include_directory)
namespace v8 {
class Object;
class V8_EXPORT StartupData {
public:
/**
* Whether the data created can be rehashed and and the hash seed can be
* recomputed when deserialized.
* Only valid for StartupData returned by SnapshotCreator::CreateBlob().
*/
bool CanBeRehashed() const;
/**
* Allows embedders to verify whether the data is valid for the current
* V8 instance.
*/
bool IsValid() const;
const char* data;
int raw_size;
};
/**
* Callback and supporting data used in SnapshotCreator to implement embedder
* logic to serialize internal fields.
* Internal fields that directly reference V8 objects are serialized without
* calling this callback. Internal fields that contain aligned pointers are
* serialized by this callback if it returns non-zero result. Otherwise it is
* serialized verbatim.
*/
struct SerializeInternalFieldsCallback {
using CallbackFunction = StartupData (*)(Local<Object> holder, int index,
void* data);
SerializeInternalFieldsCallback(CallbackFunction function = nullptr,
void* data_arg = nullptr)
: callback(function), data(data_arg) {}
CallbackFunction callback;
void* data;
};
// Note that these fields are called "internal fields" in the API and called
// "embedder fields" within V8.
using SerializeEmbedderFieldsCallback = SerializeInternalFieldsCallback;
/**
* Callback and supporting data used to implement embedder logic to deserialize
* internal fields.
*/
struct DeserializeInternalFieldsCallback {
using CallbackFunction = void (*)(Local<Object> holder, int index,
StartupData payload, void* data);
DeserializeInternalFieldsCallback(CallbackFunction function = nullptr,
void* data_arg = nullptr)
: callback(function), data(data_arg) {}
void (*callback)(Local<Object> holder, int index, StartupData payload,
void* data);
void* data;
};
using DeserializeEmbedderFieldsCallback = DeserializeInternalFieldsCallback;
/**
* Helper class to create a snapshot data blob.
*
* The Isolate used by a SnapshotCreator is owned by it, and will be entered
* and exited by the constructor and destructor, respectively; The destructor
* will also destroy the Isolate. Experimental language features, including
* those available by default, are not available while creating a snapshot.
*/
class V8_EXPORT SnapshotCreator {
public:
enum class FunctionCodeHandling { kClear, kKeep };
/**
* Initialize and enter an isolate, and set it up for serialization.
* The isolate is either created from scratch or from an existing snapshot.
* The caller keeps ownership of the argument snapshot.
* \param existing_blob existing snapshot from which to create this one.
* \param external_references a null-terminated array of external references
* that must be equivalent to CreateParams::external_references.
*/
SnapshotCreator(Isolate* isolate,
const intptr_t* external_references = nullptr,
StartupData* existing_blob = nullptr);
/**
* Create and enter an isolate, and set it up for serialization.
* The isolate is either created from scratch or from an existing snapshot.
* The caller keeps ownership of the argument snapshot.
* \param existing_blob existing snapshot from which to create this one.
* \param external_references a null-terminated array of external references
* that must be equivalent to CreateParams::external_references.
*/
SnapshotCreator(const intptr_t* external_references = nullptr,
StartupData* existing_blob = nullptr);
/**
* Destroy the snapshot creator, and exit and dispose of the Isolate
* associated with it.
*/
~SnapshotCreator();
/**
* \returns the isolate prepared by the snapshot creator.
*/
Isolate* GetIsolate();
/**
* Set the default context to be included in the snapshot blob.
* The snapshot will not contain the global proxy, and we expect one or a
* global object template to create one, to be provided upon deserialization.
*
* \param callback optional callback to serialize internal fields.
*/
void SetDefaultContext(Local<Context> context,
SerializeInternalFieldsCallback callback =
SerializeInternalFieldsCallback());
/**
* Add additional context to be included in the snapshot blob.
* The snapshot will include the global proxy.
*
* \param callback optional callback to serialize internal fields.
*
* \returns the index of the context in the snapshot blob.
*/
size_t AddContext(Local<Context> context,
SerializeInternalFieldsCallback callback =
SerializeInternalFieldsCallback());
/**
* Attach arbitrary V8::Data to the context snapshot, which can be retrieved
* via Context::GetDataFromSnapshotOnce after deserialization. This data does
* not survive when a new snapshot is created from an existing snapshot.
* \returns the index for retrieval.
*/
template <class T>
V8_INLINE size_t AddData(Local<Context> context, Local<T> object);
/**
* Attach arbitrary V8::Data to the isolate snapshot, which can be retrieved
* via Isolate::GetDataFromSnapshotOnce after deserialization. This data does
* not survive when a new snapshot is created from an existing snapshot.
* \returns the index for retrieval.
*/
template <class T>
V8_INLINE size_t AddData(Local<T> object);
/**
* Created a snapshot data blob.
* This must not be called from within a handle scope.
* \param function_code_handling whether to include compiled function code
* in the snapshot.
* \returns { nullptr, 0 } on failure, and a startup snapshot on success. The
* caller acquires ownership of the data array in the return value.
*/
StartupData CreateBlob(FunctionCodeHandling function_code_handling);
// Disallow copying and assigning.
SnapshotCreator(const SnapshotCreator&) = delete;
void operator=(const SnapshotCreator&) = delete;
private:
size_t AddData(Local<Context> context, internal::Address object);
size_t AddData(internal::Address object);
void* data_;
};
template <class T>
size_t SnapshotCreator::AddData(Local<Context> context, Local<T> object) {
T* object_ptr = *object;
internal::Address* p = reinterpret_cast<internal::Address*>(object_ptr);
return AddData(context, *p);
}
template <class T>
size_t SnapshotCreator::AddData(Local<T> object) {
T* object_ptr = *object;
internal::Address* p = reinterpret_cast<internal::Address*>(object_ptr);
return AddData(*p);
}
} // namespace v8
#endif // INCLUDE_V8_SNAPSHOT_H_
