A protobuf wire-stream is a byte string that is comprised of zero or more of the above multi-byte wire-stream primitives. Templates are lists of Prolog terms. Each term corresponds to a production rule in the DCG. The purpose of the template is to provide a recipe and value set for encoding and decoding a particular message. Each term in the template has an arity of two. The term's functor is the local "host type". Argument 1 is its tag, which must always be ground, and argument 2 is its associated value, which may or may not be ground.
Note: It is an error to attempt to encode a message using a template that is not ground. Decoding a message into a template that has unbound variables has the effect of unifying the variables with their corresponding values in the wire-stream.
Map a Prolog structure to a Protocol Buffer:
command(add(X,Y), Proto) :- Proto = protobuf([atom(1, command), atom(2, add), integer(3, X), integer(4, Y) ]).
... prepare X, Y for command ... command(add(X,Y), Proto), protobuf_message(Proto, Msg), ... send the message ...
Proto is the protobuf template. Each template describes exactly one
message. Msg is the wire-stream. If you are interworking with other
systems and languages, then the protobuf templates that you supply to
be equivalent to those described in the
.proto file that is used on the other side.