(POC) WebMessaging: Send a transferable ArrayBuffer over MessagePort by copy

Source/bindings/core/v8/custom/V8MessagePortCustom.cpp

+#include "config.h"
+#include "bindings/core/v8/SerializedScriptValueFactory.h"
+#include "bindings/core/v8/V8MessagePort.h"
+#include "core/dom/DOMArrayBuffer.h"
+#include "core/dom/ExceptionCode.h"
+
+namespace blink {
+
+static void acculumateArrayBuffersForAllWorlds(v8::Isolate* isolate, DOMArrayBuffer* object, Vector<v8::Local<v8::ArrayBuffer>, 4>& buffers)
+{
+    if (isMainThread()) {
+        Vector<RefPtr<DOMWrapperWorld>> worlds;
+        DOMWrapperWorld::allWorldsInMainThread(worlds);
+        for (size_t i = 0; i < worlds.size(); i++) {
+            v8::Local<v8::Object> wrapper = worlds[i]->domDataStore().get(object, isolate);
+            if (!wrapper.IsEmpty())
+                buffers.append(v8::Local<v8::ArrayBuffer>::Cast(wrapper));
+        }
+    } else {
+        v8::Local<v8::Object> wrapper = DOMWrapperWorld::current(isolate).domDataStore().get(object, isolate);
+        if (!wrapper.IsEmpty())
+            buffers.append(v8::Local<v8::ArrayBuffer>::Cast(wrapper));
+    }
+}
+
+typedef Vector<WTF::ArrayBufferContents, 1> ArrayBufferContentsArray;
+
+static PassOwnPtr<ArrayBufferContentsArray> neuterTransferableArrayBuffers(v8::Isolate* isolate, ArrayBufferArray& arrayBuffers, ExceptionState& exceptionState)
+{
+    OwnPtr<ArrayBufferContentsArray> contents = adoptPtr(new ArrayBufferContentsArray(arrayBuffers.size()));
+
+    HashSet<DOMArrayBufferBase*> visited;
+    for (size_t i = 0; i < arrayBuffers.size(); i++) {
+        if (visited.contains(arrayBuffers[i].get()))
+            continue;
+        visited.add(arrayBuffers[i].get());
+
+        if (arrayBuffers[i]->isShared()) {
+            // Don't have to neuter SharedArrayBuffer.
+            continue;
+        }
+
+        Vector<v8::Local<v8::ArrayBuffer>, 4> bufferHandles;
+        v8::HandleScope handleScope(isolate);
+        acculumateArrayBuffersForAllWorlds(isolate, static_pointer_cast<DOMArrayBuffer>(arrayBuffers[i]).get(), bufferHandles);
+        bool isNeuterable = true;
+        for (size_t j = 0; j < bufferHandles.size(); j++)
+            isNeuterable &= bufferHandles[j]->IsNeuterable();
+
+        RefPtr<DOMArrayBufferBase> toTransfer = arrayBuffers[i];
+        if (!isNeuterable)
+            continue;
+
+        bool result = toTransfer->transfer(contents->at(i));
+        if (!result) {
+            exceptionState.throwDOMException(DataCloneError, "ArrayBuffer at index " + String::number(i) + " could not be transferred.");
+            return nullptr;
+        }
+
+        for (size_t j = 0; j < bufferHandles.size(); j++)
+            bufferHandles[j]->Neuter();
+    }
+
+    return contents.release();
+}
+
+void V8MessagePort::postMessageMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& info)
+{
+    ExceptionState exceptionState(ExceptionState::ExecutionContext, "postMessage", "MessagePort", info.Holder(), info.GetIsolate());
+    if (UNLIKELY(info.Length() < 1)) {
+        setMinimumArityTypeError(exceptionState, 1, info.Length());
+        exceptionState.throwIfNeeded();
+        return;
+    }
+    MessagePort* messagePort = V8MessagePort::toImpl(info.Holder());
+    OwnPtrWillBeRawPtr<MessagePortArray> ports = adoptPtrWillBeNoop(new MessagePortArray);
+    ArrayBufferArray arrayBuffers;
+    if (info.Length() > 1) {
+        const int transferablesArgIndex = 1;
+        if (!SerializedScriptValue::extractTransferables(info.GetIsolate(), info[transferablesArgIndex], transferablesArgIndex, *ports, arrayBuffers, exceptionState)) {
+            exceptionState.throwIfNeeded();
+            return;
+        }
+    }
+
+    for (size_t i = 0; i < arrayBuffers.size(); i++) {
+        if (arrayBuffers[i]->isNeutered()) {
+            exceptionState.throwDOMException(DataCloneError, "ArrayBuffer at index " + String::number(i) + " is already neutered.");
+            return;
+        }
+    }
+
+    // TODO(nhiroki)
+    RefPtr<SerializedScriptValue> message = SerializedScriptValueFactory::instance().create(info.GetIsolate(), info[0], ports.get(), nullptr /* arrayBuffers */, exceptionState);
+    if (exceptionState.throwIfNeeded())
+        return;
+
+    if (!arrayBuffers.isEmpty()) {
+        neuterTransferableArrayBuffers(info.GetIsolate(), arrayBuffers, exceptionState);
+        if (exceptionState.throwIfNeeded())
+            return;
+    }
+
+    // FIXME: Only pass context/exceptionState if instance really requires it.
+    ExecutionContext* context = currentExecutionContext(info.GetIsolate());
+    messagePort->postMessage(context, message.release(), ports.get(), exceptionState);
+    exceptionState.throwIfNeeded();
+}
+
+} // namespace blink