No, the issue is one and the same. You cannot receive arbitrary serialized
bytes and determine what the message type is. You can do something
heuristically, but there is no way for you to be absolutely certain of the
message type simply by looking at encoded bytes.
Specific points in the code:
> C++
> > void
> > MessageDetector::insert (const pb::FileDescriptorSet & fDescSet,
> > const string & typeName)
> > {
> > vector<DBContainerPtr>::iterator iter =
> > std::find_if(dbContainerVec.begin(),
> > dbContainerVec.end(),
> > boost::bind(&DBContainer::operator(), _1) ==
> > typeName);
> > if (iter == dbContainerVec.end()) {
> > // Need to add the file descriptor set to the data base
> > cout << "Adding " << typeName << endl;
> > cout << fDescSet.DebugString() << endl;
> > shared_ptr<pb::SimpleDescriptorDatabase>
> > db(new pb::SimpleDescriptorDatabase);
> > for (int i = 0; i < fDescSet.file_size(); ++i) {
> > assert(db->Add(fDescSet.file(i)));
> > for (int j = 0; j < fDescSet.file(i).message_type_size();
> ++j)
> > {
> > string formalName;
> > formalName += fDescSet.file(i).has_package() ?
> > fDescSet.file(i).package() + "." : "";
> > formalName += fDescSet.file(i).message_type(j).name();
> > DBContainerPtr dbContainerElem(new
> DBContainer(formalName,
> > db));
> > dbContainerVec.push_back(dbContainerElem);
>
Here you add every message type found in the FileDescriptorSet into the list
of names.
> > }
> > }
> > }
> > }
> >
> > void
> > MessageDetector::discoverAndDump (const string & msg)
> > {
> > bool found = false;
> > for (int i = dbContainerVec.size() - 1; !found && i >= 0; --i) {
> > pb::DynamicMessageFactory factory;
> > const pb::Descriptor * desc =
> > dbContainerVec[i]->pool.FindMessageTypeByName
> > (dbContainerVec[i]->typeName);
> > std::auto_ptr<pb::Message>
> > revEngMessage(factory.GetPrototype(desc)->New());
> > revEngMessage->ParsePartialFromString(msg);
>
I glossed over the fact that you had actually used ParsePartialFromString
and call IsInitialized separately, but the effect is the same.
ParsePartialFromString will succeed on any bytes that are in the protocol
buffer encoding format. Again, this is true regardless of the source and
target message types.
> if (revEngMessage->IsInitialized()) {
>
This call _may_ return true if the message type has no required fields, or
the serialized bytes happen to contain values that correspond to the defined
required fields. It does not imply that the serialized bytes represent a
message of type dbContainerVec[i]. As such, you are likely breaking out of
the loop with the wrong message type.
> > cout << revEngMessage->DebugString() << endl;
> > found = true;
> > }
> > }
> >
> > if (!found) {
> > cout << (dbContainerVec.size() == 0 ?
> > "No valid announcement has been received" :
> > "No message found for the message")
> > << endl;
> > }
> >
> > --
> >
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