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

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

Index: third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.cpp
diff --git a/third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.cpp b/third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.cpp
index 06c7575aa6c00319bba040d5281568a38eba5b7a..085484f9e78a9d386e69ff6e34ca28f59e3a9358 100644
--- a/third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.cpp
+++ b/third_party/WebKit/Source/bindings/core/v8/SerializedScriptValue.cpp
@@ -131,9 +131,43 @@ 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());
@@ -417,7 +451,8 @@ SerializedScriptValue::transferArrayBufferContents(
 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);
 }