V8ScriptValueSerializer: Use PartitionAlloc for the buffer, and avoid copying it into a String.

third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.cpp

 /*
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 113 matching lines @@
     ASSERT(v8::Isolate::GetCurrent());
     v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(
         -m_externallyAllocatedMemory);
   }
 }
 
 PassRefPtr<SerializedScriptValue> SerializedScriptValue::nullValue() {
   return create(ScriptValueSerializer::serializeNullValue());
 }
 
+String SerializedScriptValue::toWireString() const {
+  if (!m_data.isNull())
+    return m_data;
+
+  // Add the padding '\0', but don't put it in |m_dataBuffer|.
+  // This requires direct use of uninitialized strings, though.
+  UChar* destination;
+  size_t stringSizeBytes = (m_dataBufferSize + 1) & ~1;

[haraken, 2016/11/11 03:50:01]

Shall we use CheckedNumeric<>?

[jbroman, 2016/11/11 16:14:58]

I can if you'd like, but the addition could only overflow if m_dataBufferSize
were already SIZE_MAX (which, on our supported platforms, implies that the data
buffer fills the entire virtual address space already, which is impossible), so
I don't see how this could overflow. If you would still like this, I'll switch.

+  String wireString =
+      String::createUninitialized(stringSizeBytes / 2, destination);
+  memcpy(destination, m_dataBuffer.get(), m_dataBufferSize);
+  if (stringSizeBytes > m_dataBufferSize)
+    reinterpret_cast<char*>(destination)[stringSizeBytes - 1] = '\0';
+  return wireString;
+}
+
 // Convert serialized string to big endian wire data.
 void SerializedScriptValue::toWireBytes(Vector<char>& result) const {
-  ASSERT(result.isEmpty());
+  DCHECK(result.isEmpty());
+
+  if (m_data.isNull()) {
+    size_t wireSizeBytes = (m_dataBufferSize + 1) & ~1;

[haraken, 2016/11/11 03:50:01]

Ditto.

+    result.resize(wireSizeBytes);
+
+    const UChar* src = reinterpret_cast<UChar*>(m_dataBuffer.get());
+    UChar* dst = reinterpret_cast<UChar*>(result.data());
+    for (size_t i = 0; i < m_dataBufferSize / 2; i++)
+      dst[i] = htons(src[i]);
+
+    // This is equivalent to swapping the byte order of the two bytes (x, 0),
+    // depending on endianness.
+    if (m_dataBufferSize % 1)
+      dst[wireSizeBytes / 2 - 1] = m_dataBuffer[m_dataBufferSize - 1] << 8;
+
+    return;
+  }
+
   size_t length = m_data.length();
   result.resize(length * sizeof(UChar));
   UChar* dst = reinterpret_cast<UChar*>(result.data());
 
   if (m_data.is8Bit()) {
     const LChar* src = m_data.characters8();
     for (size_t i = 0; i < length; i++)
       dst[i] = htons(static_cast<UChar>(src[i]));
   } else {
     const UChar* src = m_data.characters16();
@@ skipping 263 matching lines @@
           bufferHandle->Neuter();
       }
     }
   }
   return contents;
 }
 
 void SerializedScriptValue::registerMemoryAllocatedWithCurrentScriptContext() {
   if (m_externallyAllocatedMemory)
     return;
-  m_externallyAllocatedMemory = static_cast<intptr_t>(m_data.length());
+
+  m_externallyAllocatedMemory = static_cast<intptr_t>(dataLengthInBytes());
   v8::Isolate::GetCurrent()->AdjustAmountOfExternalAllocatedMemory(
       m_externallyAllocatedMemory);
 }
 
 }  // namespace blink