Hi! I have a problem deserializing a protobuf mess...

# serialization

[Ivan Di Sante]

Hi! I have a problem deserializing a protobuf message with kotlinx serialization.
I have this data class

@Serializable
data class ProtobufMsg(
    val type: Int,
    @SerialName("headerList") val headerList: List<HeaderSignalInfo> = emptyList(),
    @SerialName("dataList") val dataList: List<SignalsData> = emptyList(),
    @SerialName("signalsList") val signalsList: List<SignalObject> = emptyList(),
    @SerialName("serviceInfo") val serviceInfo: ServiceInfo? = null
) {
    companion object {
        // Extension function for deserializing from ByteArray
        fun parseFrom(bytes: ByteArray): ProtobufMsg {
            return Protobuf.decodeFromByteArray(serializer(), bytes)
        }

        // Extension function for deserializing from InputStream
        fun parseFrom(input: InputStream): ProtobufMsg {
            return kotlinx.serialization.json.Json.decodeFromString(serializer(), input.reader().readText())
        }

        // Extension function for deserializing from String
        fun parseFrom(str: String): ProtobufMsg {
            return kotlinx.serialization.json.Json.decodeFromString(serializer(), str)
        }
    }
}

My .proto file is like that

message ProtobufMsg{

    required int32 type = 1;
    repeated HeaderSignalInfo headerList = 2;
    repeated SignalsData dataList = 3;
    repeated SignalObject signalsList = 4;
    optional ServiceInfo  serviceInfo  = 5;


}

When i try to deserialize the bytes i receive, i get the error "Expected wire type 0, but found 7"; how can i resolve it?

I kept the json serialization cause i'm only passing ByteArray so i only need the first parseFrom() function.
I also searched on google and found that kotlin serialization use repeated as packed by default while the ones i receive might not be packed. However, how should the data class be if i want that kotlin serialization don't use repeated as packed?
Thanks

[Tim McCormack]

I don't know protobuf, but my suggestion would be to see if there's another tool that you could feed your bytes into to see if that one can decode it properly.

[Tim McCormack]

That way you could at least verify that the generated bytes are correct, at least according to one other parser. (This could be a bit of a rabbit hole, but I feel like there's probably an online tool that would make this easy.)

[CLOVIS]

There's no wire type 7 🤔 https://protobuf.dev/programming-guides/encoding/#structure

This seems to point to the direction of the bytestream being incorrect

[Ivan Di Sante]

Now i also tried generating classes with protoc compiler but it gives me "Protocol message tag had invalid wire type"

[CLOVIS]

That confirms it; it's the message that's wrong, not the code. Where are the bytes coming from?

[Ivan Di Sante]

It's a stream of bytes sent through a socket by a server

[Tim McCormack]

Not generated by your own code, then? It might not even be protobuf. (Seems like it isn't.)