CODEWITHSUNDEEP
protocprotobuf.jsprotobufjsprotocol-buffers
kpavel
kpavel

Reputation: 282

How to encode protocol buffer string to binary using protoc

I been trying to encode strings using protoc cli utility. Noticed that output still contains plain text. What am i doing wrong?

osboxes@osboxes:~/proto/bin$ cat ./teststring.proto
syntax = "proto2";
message Test2 {
  optional string b = 2;
}

echo b:\"my_testing_string\"|./protoc --encode Test2 teststring.proto>result.out

result.out contains:

^R^Qmy_testing_string

protoc versions libprotoc 3.6.0 and libprotoc 2.5.0

Upvotes: 9

Views: 11932

Answers (2)

bb7bb
bb7bb

Reputation: 31

protoc --proto_path=${protobuf_path} --encode=${protobuf_message} ${protobuf_file} < ${source_file} > ${output_file}

and in this case: 

protoc --proto_path=~/proto/bin --encode="Test2" ~/proto/bin/teststring.proto < ${source.txt} > ./output.bin

or: 

cat b:\"my_testing_string\" | protoc --proto_path=~/proto/bin --encode="Test2" ~/proto/bin/teststring.proto > ./output.bin

Upvotes: 3

Marc Gravell
Marc Gravell

Reputation: 1062600

Just to formalize in an answer:

The command as written should be fine; the output is protobuf binary - it just resembles text because protobuf uses utf-8 to encode strings, and your content is dominated by a string. However, despite this: the file isn't actually text, and you should usually use a hex viewer or similar if you need to inspect it.

If you want to understand the internals of a file, https://protogen.marcgravell.com/decode is a good resource - it rips an input file or hex string following the protocol rules, and tells you what each byte means (field headers, length prefixes, payloads, etc).

I'm guessing your file is actually:

(hex) 10 11 6D 79 5F etc

i.e. 0x10 = "field 2, length prefixed", 0x11 = 17 (the payload length, encoded as varint), then "my_testing_string" encoded as 17 bytes of UTF8.

Upvotes: 3

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