CODEWITHSUNDEEP
.netprotocol-buffersprotobuf-net
AcidPAT
AcidPAT

Reputation: 709

ProtoBuf-Net to do raw read

I want to have a simple piece of code that will iterate through a random stream of protocol buffers, and print out the contents without having an explicit understanding of the structural contents. Something that is equivalent to XmlReader.Read() inside a while loop

using (ProtoBuf.ProtoReader protoReader = 
      new ProtoBuf.ProtoReader(stream1, null, 
            new ProtoBuf.SerializationContext { }))
{
    protoReader.ReadFieldHeader();
    while (protoReader.WireType != ProtoBuf.WireType.None)
    {
       switch (protoReader.WireType)
       {
       case ProtoBuf.WireType.Fixed64:
           Console.WriteLine(protoReader.ReadInt64());
           break;
       case ProtoBuf.WireType.Fixed32:
           Console.WriteLine(protoReader.ReadInt32());
           break;
       case ProtoBuf.WireType.StartGroup:
           Console.WriteLine(protoReader.ReadInt32());
           break;
       default:
           Console.WriteLine(protoReader.WireType);
           break;
       }
    }
}

However I don't know how to advance the protocol buffer to the next element. In my test, it keeps returning "StartGroup" and never advancing. How can I advance to the next element in the stream?

Upvotes: 1

Views: 745

Answers (1)

Marc Gravell
Marc Gravell

Reputation: 1064204

The ReadFieldHeader() should be inside the loop:

while(protoReader.ReadFieldHeader() > 0)
{
    //...
}

Note: if you don't know how to process a given field, there is a .SkipField() method that will correctly read the data - for example:

default:
    Console.WriteLine(protoReader.WireType);
    protoReader.SkipField();
    break;

you must read or skip the data exactly once per field-header.

In the case of groups and sub-items, you need to use StartSubItem etc:

var tok = ProtoReader.StartSubItem(protoReader);
// an inner while-loop, etc
ProtoReader.EndSubItem(tok);

alternatively: use SkipField().

Upvotes: 1

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