ValueSerializer: Replace use of std::vector with a delegate-allocated buffer.

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>
 
@@ skipping 41 matching lines @@
 
   /*
    * 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_); }
+  std::vector<uint8_t> ReleaseBuffer();
+
+  /*
+   * Returns the buffer, allocated via the delegate, and its size.
+   * Caller assumes ownership of the buffer.
+   */
+  std::pair<uint8_t*, size_t> Release();
 
   /*
    * Marks an ArrayBuffer as havings its contents transferred out of band.
    * Pass the corresponding JSArrayBuffer in the deserializing context to
    * ValueDeserializer::TransferArrayBuffer.
    */
   void TransferArrayBuffer(uint32_t transfer_id,
                            Handle<JSArrayBuffer> array_buffer);
 
   /*
    * Publicly exposed wire format writing methods.
    * These are intended for use within the delegate's WriteHostObject method.
    */
   void WriteUint32(uint32_t value);
   void WriteUint64(uint64_t value);
   void WriteRawBytes(const void* source, size_t length);
   void WriteDouble(double value);
 
  private:
+  // Managing allocations of the internal buffer.
+  void ExpandBuffer(size_t required_capacity);
+
   // Writing the wire format.
   void WriteTag(SerializationTag tag);
   template <typename T>
   void WriteVarint(T value);
   template <typename T>
   void WriteZigZag(T value);
   void WriteOneByteString(Vector<const uint8_t> chars);
   void WriteTwoByteString(Vector<const uc16> chars);
   uint8_t* ReserveRawBytes(size_t bytes);
 
@@ skipping 27 matching lines @@
   /*
    * Asks the delegate to handle an error that occurred during data cloning, by
    * throwing an exception appropriate for the host.
    */
   void ThrowDataCloneError(MessageTemplate::Template template_index);
   V8_NOINLINE void ThrowDataCloneError(MessageTemplate::Template template_index,
                                        Handle<Object> arg0);
 
   Isolate* const isolate_;
   v8::ValueSerializer::Delegate* const delegate_;
-  std::vector<uint8_t> buffer_;
+  uint8_t* buffer_ = nullptr;
+  size_t buffer_size_ = 0;
+  size_t buffer_capacity_ = 0;
   Zone zone_;
 
   // To avoid extra lookups in the identity map, ID+1 is actually stored in the
   // map (checking if the used identity is zero is the fast way of checking if
   // the entry is new).
   IdentityMap<uint32_t> id_map_;
   uint32_t next_id_ = 0;
 
   // A similar map, for transferred array buffers.
   IdentityMap<uint32_t> array_buffer_transfer_map_;
@@ skipping 119 matching lines @@
   Handle<FixedArray> id_map_;
   MaybeHandle<SeededNumberDictionary> array_buffer_transfer_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ValueDeserializer);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_VALUE_SERIALIZER_H_