Question

I’m using protobuf-csharp-port and I need the ability to record some protobuf messages for replay later. XML would be ideal for me, but I’m flexible as long as a human could go into the file, make changes, then replay the messages from the file.

Using this C# code:

        MyRequest req =
            MyRequest.CreateBuilder().SetStr("Lafayette").Build();

        using (var stringWriter = new StringWriter())
        {
            var xmlWriterSettings = new XmlWriterSettings
                {
                    ConformanceLevel = ConformanceLevel.Fragment
                };

            var xmlWriter = XmlWriter.Create(stringWriter, xmlWriterSettings);

            ICodedOutputStream output = XmlFormatWriter.CreateInstance(xmlWriter);
            req.WriteTo(output);
            output.Flush();
            string xml = stringWriter.ToString();

            using (var streamWriter = new StreamWriter(@"Requests.txt"))
            {
                streamWriter.WriteLine(xml);
                streamWriter.WriteLine(xml);
                streamWriter.WriteLine(xml);
            }
        }

I produce the Requests.txt file containing:

<str>Lafayette</str>
<str>Lafayette</str>
<str>Lafayette</str>

However when I try to deserialize them back using:

        var xmlReaderSettings = new XmlReaderSettings
        {
            ConformanceLevel = ConformanceLevel.Fragment
        };

        using (var xmlReader = XmlReader.Create(@"Requests.txt", xmlReaderSettings))
        {
            ICodedInputStream input = XmlFormatReader.CreateInstance(xmlReader);
            MyRequest reqFromFile;

            while(!input.IsAtEnd)
            {
                reqFromFile =
                    ReverseRequest.CreateBuilder().MergeFrom(input).Build();
            }
        }

Only one MyRequest gets deserialized and the other two are ignored. (After reqFromFile is built, input.IsAtEnd == true.)

So back to my question: is there some way to read multiple human-readable protobuf messages from a file?

Answer 1

So back to my question: is there some way to read multiple human-readable protobuf messages from a file?

Well you’re currently creating a single text file with multiple root elements – it’s not a valid XML file.

The simplest approach would probably be to create a single XML document with all those requests in, then load it (e.g. with LINQ to XML) and create an XmlReader positioned at each of the root element’s children. Each of those XmlReader objects should be able to then deserialize to a single protobuf message.