Add same-thread stream transfer support

dom/base/StructuredCloneHolder.cpp

@@ -138,6 +138,120 @@ StructuredCloneCallbacksError(JSContext* aCx,
   NS_WARNING("Failed to clone data.");
 }
 
+struct SameThreadStreamTransferData
+{
+  SameThreadStreamTransferData(JSContext* aCx, JS::HandleObject aRecord)
+    : mRecord(aCx, aRecord)
+  {}
+
+  ~SameThreadStreamTransferData()
+  {
+    mRecord.reset();
+  }
+
+  JS::PersistentRootedObject mRecord;
+};
+
+bool
+CallStreamTransferHelper(JSContext* aCx,
+                         const char* aHelperName,
+                         JS::HandleValue aArgument,
+                         JS::MutableHandleValue aResult)
+{
+  JS::Rooted<JSObject*> global(aCx, JS::CurrentGlobalOrNull(aCx));
+  if (!global) {
+    return false;
+  }
+
+  // Resolve the stream extras lazily before looking up the internal helper.
+  JS::Rooted<JS::Value> ignored(aCx);
+  if (!JS_GetProperty(aCx, global, "WritableStream", &ignored)) {
+    return false;
+  }
+
+  JS::Rooted<JS::Value> helper(aCx);
+  if (!JS_GetProperty(aCx, global, aHelperName, &helper)) {
+    return false;
+  }
+
+  if (!helper.isObject() || !JS::IsCallable(&helper.toObject())) {
+    aResult.setUndefined();
+    return true;
+  }
+
+  JS::Rooted<JS::Value> argument(aCx, aArgument);
+  if (!JS_WrapValue(aCx, &argument)) {
+    return false;
+  }
+
+  return JS::Call(aCx, JS::UndefinedHandleValue, helper,
+                  JS::HandleValueArray(argument), aResult);
+}
+
+bool
+TryWriteSameThreadStreamTransfer(JSContext* aCx,
+                                 JS::Handle<JSObject*> aObj,
+                                 const char* aHelperName,
+                                 uint32_t aTransferTag,
+                                 uint32_t* aTag,
+                                 JS::TransferableOwnership* aOwnership,
+                                 void** aContent,
+                                 uint64_t* aExtraData,
+                                 bool* aHandled)
+{
+  *aHandled = false;
+
+  JS::Rooted<JS::Value> argument(aCx, JS::ObjectValue(*aObj));
+  JS::Rooted<JS::Value> transferRecord(aCx);
+  if (!CallStreamTransferHelper(aCx, aHelperName, argument, &transferRecord)) {
+    return false;
+  }
+
+  if (transferRecord.isUndefined()) {
+    return true;
+  }
+
+  if (!transferRecord.isObject()) {
+    return false;
+  }
+
+  JS::Rooted<JSObject*> record(aCx, &transferRecord.toObject());
+  SameThreadStreamTransferData* data =
+    new SameThreadStreamTransferData(aCx, record);
+
+  *aTag = aTransferTag;
+  *aOwnership = JS::SCTAG_TMO_CUSTOM;
+  *aContent = data;
+  *aExtraData = 0;
+  *aHandled = true;
+  return true;
+}
+
+bool
+ReadSameThreadStreamTransfer(JSContext* aCx,
+                             void* aContent,
+                             const char* aHelperName,
+                             JS::MutableHandleObject aReturnObject)
+{
+  MOZ_ASSERT(aContent);
+  SameThreadStreamTransferData* data =
+    static_cast<SameThreadStreamTransferData*>(aContent);
+
+  JS::Rooted<JS::Value> record(aCx, JS::ObjectValue(*data->mRecord));
+  JS::Rooted<JS::Value> result(aCx);
+  if (!CallStreamTransferHelper(aCx, aHelperName, record, &result)) {
+    return false;
+  }
+
+  if (!result.isObject()) {
+    return false;
+  }
+
+  aReturnObject.set(&result.toObject());
+  delete data;
+  return true;
+}
+
 } // anonymous namespace
 
 const JSStructuredCloneCallbacks StructuredCloneHolder::sCallbacks = {
@@ -1375,6 +1489,20 @@ StructuredCloneHolder::CustomReadTransferHandler(JSContext* aCx,
     return true;
   }
 
+  if (mStructuredCloneScope == StructuredCloneScope::SameProcessSameThread) {
+    if (aTag == SCTAG_DOM_TRANSFERRED_WRITABLESTREAM) {
+      return ReadSameThreadStreamTransfer(aCx, aContent,
+                                          "__uxpReceiveWritableStreamTransfer",
+                                          aReturnObject);
+    }
+
+    if (aTag == SCTAG_DOM_TRANSFERRED_READABLESTREAM) {
+      return ReadSameThreadStreamTransfer(aCx, aContent,
+                                          "__uxpReceiveReadableStreamTransfer",
+                                          aReturnObject);
+    }
+  }
+
   return false;
 }
 
@@ -1443,6 +1571,31 @@ StructuredCloneHolder::CustomWriteTransferHandler(JSContext* aCx,
     }
   }
 
+  if (mStructuredCloneScope == StructuredCloneScope::SameProcessSameThread) {
+    bool handled = false;
+    if (!TryWriteSameThreadStreamTransfer(aCx, obj,
+                                          "__uxpTransferWritableStream",
+                                          SCTAG_DOM_TRANSFERRED_WRITABLESTREAM,
+                                          aTag, aOwnership, aContent,
+                                          aExtraData, &handled)) {
+      return false;
+    }
+    if (handled) {
+      return true;
+    }
+
+    if (!TryWriteSameThreadStreamTransfer(aCx, obj,
+                                          "__uxpTransferReadableStream",
+                                          SCTAG_DOM_TRANSFERRED_READABLESTREAM,
+                                          aTag, aOwnership, aContent,
+                                          aExtraData, &handled)) {
+      return false;
+    }
+    if (handled) {
+      return true;
+    }
+  }
+
   return false;
 }
 
@@ -1480,6 +1633,16 @@ StructuredCloneHolder::CustomFreeTransferHandler(uint32_t aTag,
     delete data;
     return;
   }
+
+  if ((aTag == SCTAG_DOM_TRANSFERRED_WRITABLESTREAM ||
+       aTag == SCTAG_DOM_TRANSFERRED_READABLESTREAM) &&
+      mStructuredCloneScope == StructuredCloneScope::SameProcessSameThread) {
+    MOZ_ASSERT(aContent);
+    SameThreadStreamTransferData* data =
+      static_cast<SameThreadStreamTransferData*>(aContent);
+    delete data;
+    return;
+  }
 }
 
 bool