Blink-compatible serialization of oddball values.

src/value-serializer.h

+// Copyright 2016 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 V8_VALUE_SERIALIZER_H_
+#define V8_VALUE_SERIALIZER_H_
+
+#include <cstdint>
+#include <vector>
+
+#include "include/v8.h"
+#include "src/base/compiler-specific.h"
+#include "src/base/macros.h"
+#include "src/vector.h"
+
+namespace v8 {
+namespace internal {
+
+class Isolate;
+class Object;
+class Oddball;
+
+enum class SerializationTag : uint8_t;
+
+/**
+ * Writes V8 objects in a binary format that allows the objects to be cloned
+ * according to the HTML structured clone algorithm.
+ *
+ * Format is based on Blink's previous serialization logic.
+ */

[Camillo Bruni, 2016/08/12 09:54:44]

I wish all V8 classes were that nicely documented *sigh*  ;)

+class ValueSerializer {
+ public:
+  ValueSerializer();
+  ~ValueSerializer();
+
+  /*
+   * Writes out a header, which includes the format version.
+   */
+  void WriteHeader();
+
+  /*
+   * Serializes a V8 object into the buffer.
+   */
+  Maybe<bool> WriteObject(Handle<Object> object) WARN_UNUSED_RESULT;
+
+  /*
+   * Returns the stored data. This serializer should not be used once the buffer
+   * is released. The contents are undefined if a previous write has failed.
+   */
+  std::vector<uint8_t> ReleaseBuffer() { return std::move(buffer_); }
+
+ private:
+  // Writing the wire format.
+  void WriteTag(SerializationTag tag);
+  template <typename T>

[Camillo Bruni, 2016/08/12 09:54:44]

nit: Could you add a comment what WriteVarint does (or add inline comments in
the function definition.

[jbroman, 2016/08/12 15:16:34]

Added comments inline, with a link to the protobuf encoding page (this, and
zigzag which is used for signed integers, are encoded the same way as in
protobuf, and they have a nice page that explains it clearly).

[jbroman, 2016/08/12 15:16:34]

Added comments inline, with a link to the protobuf encoding page (this, and
zigzag which is used for signed integers, are encoded the same way as in
protobuf, and they have a nice page that explains it clearly).

+  void WriteVarint(T value);
+
+  // Writing V8 objects of various kinds.
+  void WriteOddball(Oddball* oddball);
+
+  std::vector<uint8_t> buffer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ValueSerializer);
+};
+
+/*
+ * Deserializes values from data written with ValueSerializer, or a compatible
+ * implementation.
+ */
+class ValueDeserializer {
+ public:
+  ValueDeserializer(Isolate* isolate, Vector<const uint8_t> data);
+  ~ValueDeserializer();
+
+  /*
+   * Runs version detection logic, which may fail if the format is invalid.
+   */
+  Maybe<bool> ReadHeader() WARN_UNUSED_RESULT;
+
+  /*
+   * Deserializes a V8 object from the buffer.
+   */
+  MaybeHandle<Object> ReadObject() WARN_UNUSED_RESULT;
+
+ private:
+  Maybe<SerializationTag> ReadTag() WARN_UNUSED_RESULT;
+  template <typename T>
+  Maybe<T> ReadVarint() WARN_UNUSED_RESULT;
+
+  Isolate* const isolate_;
+  const uint8_t* position_;
+  const uint8_t* const end_;
+  uint32_t version_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(ValueDeserializer);
+};
+
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_VALUE_SERIALIZER_H_