How to decode raw proto byte array

Question

Using HttpClient I can get the byte array data where it's a protocol buffer. How to decode it using protobuf-net without knowing the type? This stackoverflow answer doesn't work anymore in the latest version where I can't instantiate the ProtoReader.

Answer 1

You can still instantiate the reader API in v3. The only difference is that you should useCreate rather than new, and if at all possible: use the new ProtoReader.State API instead. Other than that, it should stay largely the same. Plus you don't need a MemoryStream any more (you can use raw buffers such as a byte[] directly).

Here's a translated version using v3 and the State API:

static void Main()
{
    byte[] arr = // ...
    var reader = ProtoReader.State.Create(arr, null, null);
    try
    {
        WriteTree(ref reader);
    }
    finally
    {   // the rules on when you can "using" a ref-type
        // are ... complicated
        reader.Dispose();
    }
}
static void WriteTree(ref ProtoReader.State reader)
{
    while (reader.ReadFieldHeader() > 0)
    {
        Console.WriteLine(reader.FieldNumber);
        Console.WriteLine(reader.WireType);
        switch (reader.WireType)
        {
            case WireType.Varint:
                // warning: this appear to be wrong if the 
                // value was written signed ("zigzag") - to
                // read zigzag, add: pr.Hint(WireType.SignedVariant);
                Console.WriteLine(reader.ReadInt64());
                break;
            case WireType.String:
                // note: "string" here just means "some bytes"; could
                // be UTF-8, could be a BLOB, could be a "packed array",
                // or could be sub-object(s); showing UTF-8 for simplicity
                Console.WriteLine(reader.ReadString());
                break;
            case WireType.Fixed32:
                // could be an integer, but probably floating point
                Console.WriteLine(reader.ReadSingle());
                break;
            case WireType.Fixed64:
                // could be an integer, but probably floating point
                Console.WriteLine(reader.ReadDouble());
                break;
            case WireType.StartGroup:
                // one of 2 sub-object formats
                var tok = reader.StartSubItem();
                WriteTree(ref reader);
                reader.EndSubItem(tok);
                break;
            default:
                reader.SkipField();
                break;
        }
    }
}

(the non-State API is still usable, but this is preferred)