Google-protobuf: How to create unions using Google protocol buffer

Question

I am currently trying to use Google Protocol Buffers for C language. I am a little unsure as to how to create a C union using GPB.

For example, with a proto file as follows:

message msgToSend
{
 required Type msg_type=1; //Type is a predefined enum to determine message type
 optional ReqMsg1 msg1=2;
 optional ReqMsg2 msg2=3;
}

I expect above to generate a union upon compilation but a structure is generated as follows:

struct _msgToSend
{
 ProtobufCMessage base;
 Type msg_type;
 ReqMsg1 msg1;
 ReqMsg2 msg2;
}

Answer 1

In protobuf there is a dedicated structure for that (I'm using it in C++ though, not sure if it will work in pure C):

message MyUnion {
    oneof MyUnionOneof {
        bool booleanValue = 1;
        string stringValue = 2;
    }
}

Check out this link: https://developers.google.com/protocol-buffers/docs/proto#oneof