Very nice! Puts together many of my favorite protobuf techniques. I am glad that people do not feel that they are required to use generated code when they choose the protobuf format.

One thing I will quibble about is the representation of the tag number 19, named SrcCountry. The author shows it as binary 10011010 but this is impossible because protobuf tags are themselves encoded as continuation bit variable-length numbers and cannot end in a byte with the most significant bit set. That's why fields 1-15 are the magic fast-path fields taking only 1 byte. Field 19 would need two bytes... 10000001_00011010 or in hex 81 1A