How to serialize empty message in protobuf-3 in C++?

[Ivan Baidakou]

Hi,

There is a the following message type:

message Ping {}

When I invoke for my  object  "proto::Ping &ping" the ping.ByteSizeLong() it returns zero. ping.SerializeAsString() also returns empty string.

What can be done?

Thank you,
wbr, basiliscos

[Nadav Samet]

Hi Ivan,

You are doing it correctly. An empty message has zero length when serialized. This is also true for messages with only optional fields - an empty array of bytes is a valid serialized instance of such a message.

-Nadav

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-Nadav

[Ivan Baidakou]

Hi Nadav,

I have to send the message over the network. If it returns the empty string, there is nothing to send. Anyway, I can see, that the remote side somehow sends (empty) Pings to me. How I can do the same?

[Nadav Samet]

Over the network, you could send the size of the message (which may be zero) and then the message itself. See the example on this page and steaming multiple messages. 

To view this discussion on the web visit https://groups.google.com/d/msgid/protobuf/4990bfa4-20a8-445b-b402-fbb134cde708n%40googlegroups.com.

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-Nadav

[Ivan Baidakou]

Thanks a lot, it helped greatly!