Beware the unpacked repeated field

The last consideration is not helpful for our TODO API but is worth mentioning. In Protobuf, we have different ways of encoding repeated fields. We have packed and unpacked repeated fields.

Packed repeated fields

To understand, let us see an example of a packed repeated field. Let us say that we have the following message:

message RepeatedUInt32Values {
  repeated uint32 values = 1;
}

It is a simple list of the uint32 scalar type. If we serialized this with the values 1, 2, and 3, we would get the following result:

$ cat repeated_scalar.txt | protoc --encode=
 RepeatedUInt32Values proto/repeated.proto | hexdump -C
0a 03 01 02 03
00000005

repeated_scalar.txt from the preceding command contains the following:

values: 1
values: 2
values: 3

This is an example of a packed repeated field because of how the field wraps multiple values. You might think that this is normal since this is a list, but we are going to see later...