person.proto

syntax = "proto3";
package tutorial;
message Person {
enum Corpus {
    UNIVERSAL = 0;
    WEB = 1;
    IMAGES = 2;
    LOCAL = 3;
    NEWS = 4;
    PRODUCTS = 5;
    VIDEO6 = 6;
    VIDEO7 = 7;
    VIDEO8 = 8;
    VIDEO9 = 9;
    VIDEO10 = 10;
    VIDEO11 = 11;
    VIDEO12 = 12;
    VIDEO13 = 13;
    VIDEO14 = 14;
  }
  Corpus corpus = 1;
  Corpus corpus2 = 2;
  Corpus corpus3 = 4;
  Corpus corpus4 = 5;
  sfixed64 fix = 3;  //Always eight bytes.
}

proto.kt

val person =
            PersonOuterClass.Person.newBuilder()
                .setCorpus(PersonOuterClass.Person.Corpus.NEWS)
                //.setCorpus2(PersonOuterClass.Person.Corpus.NEWS)
                //.setCorpus3(PersonOuterClass.Person.Corpus.NEWS)
                //.setCorpus4(PersonOuterClass.Person.Corpus.NEWS)
                //.setFix(123)
                .build()
        Timber.d(
            ">>> proto byteArray " + person.toByteArray() + ", size " + person.toByteArray
                ().size
        )

size

enum * 4 + int = 17
enum * 3 + int = 15
enum * 2 + int = 13
enum * 1 + int = 11
enum * 1 = 2


sfixed64 = 8 bytes
each new field cost 1 byte


enum * 4 + int = 17  (enum 1 byte * 4, sfixed64 8, 5 fields 4 + 8 + 5 = 17)
enum * 3 + int = 15
enum * 2 + int = 13
enum * 1 + int = 11
enum * 1 = 2 (enum 1 byte * 1, 1 field 1+1 = 2)