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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_VALUE_SERIALIZER_H_
 #define INCLUDE_V8_VALUE_SERIALIZER_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <utility>
 
 #include "v8-local-handle.h"  // NOLINT(build/include_directory)
 #include "v8-maybe.h"         // NOLINT(build/include_directory)
 #include "v8config.h"         // NOLINT(build/include_directory)
 
 namespace v8 {
 
 class ArrayBuffer;
 class Isolate;
 class Object;
 class SharedArrayBuffer;
 class String;
 class WasmModuleObject;
 class Value;
 
 namespace internal {
 struct ScriptStreamingData;
 class SharedObjectConveyorHandles;
 class ValueDeserializer;
 class ValueSerializer;
 }  // namespace internal
 
 /**
  * A move-only class for managing the lifetime of shared value conveyors used
  * by V8 to keep JS shared values alive in transit when serialized.
  *
  * This class is not directly constructible and is always passed to a
  * ValueSerializer::Delegate via ValueSerializer::SetSharedValueConveyor.
  *
  * The embedder must not destruct the SharedValueConveyor until the associated
  * serialized data will no longer be deserialized.
  */
 class V8_EXPORT SharedValueConveyor final {
  public:
   SharedValueConveyor(SharedValueConveyor&&) noexcept;
   ~SharedValueConveyor();
 
   SharedValueConveyor& operator=(SharedValueConveyor&&) noexcept;
 
  private:
   friend class internal::ValueSerializer;
   friend class internal::ValueDeserializer;
 
   explicit SharedValueConveyor(Isolate* isolate);
 
   std::unique_ptr<internal::SharedObjectConveyorHandles> private_;
 };
 
 /**
  * Value serialization compatible with the HTML structured clone algorithm.
  * The format is backward-compatible (i.e. safe to store to disk).
  */
 class V8_EXPORT ValueSerializer {
  public:
   class V8_EXPORT Delegate {
    public:
     virtual ~Delegate() = default;
 
     /**
      * Handles the case where a DataCloneError would be thrown in the structured
      * clone spec. Other V8 embedders may throw some other appropriate exception
      * type.
      */
     virtual void ThrowDataCloneError(Local<String> message) = 0;
 
     /**
      * The embedder overrides this method to enable custom host object filter
      * with Delegate::IsHostObject.
      *
      * This method is called at most once per serializer.
      */
     virtual bool HasCustomHostObject(Isolate* isolate);
 
     /**
      * The embedder overrides this method to determine if an JS object is a
      * host object and needs to be serialized by the host.
      */
     virtual Maybe<bool> IsHostObject(Isolate* isolate, Local<Object> object);
 
     /**
      * The embedder overrides this method to write some kind of host object, if
      * possible. If not, a suitable exception should be thrown and
      * Nothing<bool>() returned.
      */
     virtual Maybe<bool> WriteHostObject(Isolate* isolate, Local<Object> object);
 
     /**
      * Called when the ValueSerializer is going to serialize a
      * SharedArrayBuffer object. The embedder must return an ID for the
      * object, using the same ID if this SharedArrayBuffer has already been
      * serialized in this buffer. When deserializing, this ID will be passed to
      * ValueDeserializer::GetSharedArrayBufferFromId as |clone_id|.
      *
      * If the object cannot be serialized, an
      * exception should be thrown and Nothing<uint32_t>() returned.
      */
     virtual Maybe<uint32_t> GetSharedArrayBufferId(
         Isolate* isolate, Local<SharedArrayBuffer> shared_array_buffer);
 
     virtual Maybe<uint32_t> GetWasmModuleTransferId(
         Isolate* isolate, Local<WasmModuleObject> module);
 
     /**
      * Called when the first shared value is serialized. All subsequent shared
      * values will use the same conveyor.
      *
      * The embedder must ensure the lifetime of the conveyor matches the
      * lifetime of the serialized data.
      *
      * If the embedder supports serializing shared values, this method should
      * return true. Otherwise the embedder should throw an exception and return
      * false.
      *
      * This method is called at most once per serializer.
      */
     virtual bool AdoptSharedValueConveyor(Isolate* isolate,
                                           SharedValueConveyor&& conveyor);
 
     /**
      * Allocates memory for the buffer of at least the size provided. The actual
      * size (which may be greater or equal) is written to |actual_size|. If no
      * buffer has been allocated yet, nullptr will be provided.
      *
      * If the memory cannot be allocated, nullptr should be returned.
      * |actual_size| will be ignored. It is assumed that |old_buffer| is still
      * valid in this case and has not been modified.
      *
      * The default implementation uses the stdlib's `realloc()` function.
      */
     virtual void* ReallocateBufferMemory(void* old_buffer, size_t size,
                                          size_t* actual_size);
 
     /**
      * Frees a buffer allocated with |ReallocateBufferMemory|.
      *
      * The default implementation uses the stdlib's `free()` function.
      */
     virtual void FreeBufferMemory(void* buffer);
   };
 
   explicit ValueSerializer(Isolate* isolate);
   ValueSerializer(Isolate* isolate, Delegate* delegate);
   ~ValueSerializer();
 
   /**
    * Writes out a header, which includes the format version.
    */
   void WriteHeader();
 
   /**
    * Serializes a JavaScript value into the buffer.
    */
   V8_WARN_UNUSED_RESULT Maybe<bool> WriteValue(Local<Context> context,
                                                Local<Value> value);
 
   /**
    * Returns the stored data (allocated using the delegate's
    * ReallocateBufferMemory) and its size. This serializer should not be used
    * once the buffer is released. The contents are undefined if a previous write
    * has failed. Ownership of the buffer is transferred to the caller.
    */
   V8_WARN_UNUSED_RESULT std::pair<uint8_t*, size_t> Release();
 
   /**
    * Marks an ArrayBuffer as havings its contents transferred out of band.
    * Pass the corresponding ArrayBuffer in the deserializing context to
    * ValueDeserializer::TransferArrayBuffer.
    */
   void TransferArrayBuffer(uint32_t transfer_id,
                            Local<ArrayBuffer> array_buffer);
 
   /**
    * Indicate whether to treat ArrayBufferView objects as host objects,
    * i.e. pass them to Delegate::WriteHostObject. This should not be
    * called when no Delegate was passed.
    *
    * The default is not to treat ArrayBufferViews as host objects.
    */
   void SetTreatArrayBufferViewsAsHostObjects(bool mode);
 
   /**
    * Write raw data in various common formats to the buffer.
    * Note that integer types are written in base-128 varint format, not with a
    * binary copy. For use during an override of Delegate::WriteHostObject.
    */
   void WriteUint32(uint32_t value);
   void WriteUint64(uint64_t value);
   void WriteDouble(double value);
   void WriteRawBytes(const void* source, size_t length);
 
   ValueSerializer(const ValueSerializer&) = delete;
   void operator=(const ValueSerializer&) = delete;
 
  private:
   struct PrivateData;
   PrivateData* private_;
 };
 
 /**
  * Deserializes values from data written with ValueSerializer, or a compatible
  * implementation.
  */
 class V8_EXPORT ValueDeserializer {
  public:
   class V8_EXPORT Delegate {
    public:
     virtual ~Delegate() = default;
 
     /**
      * The embedder overrides this method to read some kind of host object, if
      * possible. If not, a suitable exception should be thrown and
      * MaybeLocal<Object>() returned.
      */
     virtual MaybeLocal<Object> ReadHostObject(Isolate* isolate);
 
     /**
      * Get a WasmModuleObject given a transfer_id previously provided
      * by ValueSerializer::Delegate::GetWasmModuleTransferId
      */
     virtual MaybeLocal<WasmModuleObject> GetWasmModuleFromId(
         Isolate* isolate, uint32_t transfer_id);
 
     /**
      * Get a SharedArrayBuffer given a clone_id previously provided
      * by ValueSerializer::Delegate::GetSharedArrayBufferId
      */
     virtual MaybeLocal<SharedArrayBuffer> GetSharedArrayBufferFromId(
         Isolate* isolate, uint32_t clone_id);
 
     /**
      * Get the SharedValueConveyor previously provided by
      * ValueSerializer::Delegate::AdoptSharedValueConveyor.
      */
     virtual const SharedValueConveyor* GetSharedValueConveyor(Isolate* isolate);
   };
 
   ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size);
   ValueDeserializer(Isolate* isolate, const uint8_t* data, size_t size,
                     Delegate* delegate);
   ~ValueDeserializer();
 
   /**
    * Reads and validates a header (including the format version).
    * May, for example, reject an invalid or unsupported wire format.
    */
   V8_WARN_UNUSED_RESULT Maybe<bool> ReadHeader(Local<Context> context);
 
   /**
    * Deserializes a JavaScript value from the buffer.
    */
   V8_WARN_UNUSED_RESULT MaybeLocal<Value> ReadValue(Local<Context> context);
 
   /**
    * Accepts the array buffer corresponding to the one passed previously to
    * ValueSerializer::TransferArrayBuffer.
    */
   void TransferArrayBuffer(uint32_t transfer_id,
                            Local<ArrayBuffer> array_buffer);
 
   /**
    * Similar to TransferArrayBuffer, but for SharedArrayBuffer.
    * The id is not necessarily in the same namespace as unshared ArrayBuffer
    * objects.
    */
   void TransferSharedArrayBuffer(uint32_t id,
                                  Local<SharedArrayBuffer> shared_array_buffer);
 
   /**
    * Must be called before ReadHeader to enable support for reading the legacy
    * wire format (i.e., which predates this being shipped).
    *
    * Don't use this unless you need to read data written by previous versions of
    * blink::ScriptValueSerializer.
    */
   void SetSupportsLegacyWireFormat(bool supports_legacy_wire_format);
 
   /**
    * Reads the underlying wire format version. Likely mostly to be useful to
    * legacy code reading old wire format versions. Must be called after
    * ReadHeader.
    */
   uint32_t GetWireFormatVersion() const;
 
   /**
    * Reads raw data in various common formats to the buffer.
    * Note that integer types are read in base-128 varint format, not with a
    * binary copy. For use during an override of Delegate::ReadHostObject.
    */
   V8_WARN_UNUSED_RESULT bool ReadUint32(uint32_t* value);
   V8_WARN_UNUSED_RESULT bool ReadUint64(uint64_t* value);
   V8_WARN_UNUSED_RESULT bool ReadDouble(double* value);
   V8_WARN_UNUSED_RESULT bool ReadRawBytes(size_t length, const void** data);
 
   ValueDeserializer(const ValueDeserializer&) = delete;
   void operator=(const ValueDeserializer&) = delete;
 
  private:
   struct PrivateData;
   PrivateData* private_;
 };
 
 }  // namespace v8
 
 #endif  // INCLUDE_V8_VALUE_SERIALIZER_H_

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