Pfthb

Is there a way to get something like an ID for a protobuf message.

E.g. I have:

syntax = "proto3";

package protobuf;

message parameters_t

 string audio_device = 1;


message master_t

 enum type_t
 
 unknown = 0;
 login_rsp = 1;
 

 type_t type = 1;

What I want to do in C++ is send the size over the wire, then some ID of the message and the the buffer.

E.g. paramters_t is ID 0 (statically accessible) and master_t is ID 1, so I can do in my code:

if (id == protobuf::master_t::id) 
 ...

else if (id == protobuf::paramters_t::id) 
 ...

Is there any way to achieve this without manually assigning the values? I want that to be set in the protofile somehow. It can be a constant I define myself, i dont care.

A typical way is to just define an enum:

enum MsgId 
 MSGID_MASTER = 0;
 MSGID_PARAMETERS = 1;

You can then access them in C++ like constants.

What I have done to solve this now is this (arguably not very elegant) solution of putting an enum in every message like this:

enum pt

 invalid = 0;
 packet_type = 3;

This enum is in every message, but with another value for packet_type. It looks like this:

syntax = "proto3";

package protobuf;

message parameters_t

 enum pt
 
 invalid = 0;
 packet_type = 1;
 
 string audio_device = 1;


message login_message_t

 enum pt
 
 invalid = 0;
 packet_type = 2;
 

 enum process_type_t
 
 invalid_process = 0;
 player = 1;
 display = 2;
 

 process_type_t process_type = 1;
 uint32 player_id = 2;


message generic_message_t

 enum pt
 
 invalid = 0;
 packet_type = 3;
 
 enum type_t
 
 unknown = 0;
 login_done = 1;
 audio_init_success = 2;
 

 type_t type = 1;


message error_message_t

 enum pt
 
 invalid = 0;
 packet_type = 4;
 

 enum error_t
 
 unknown = 0;
 could_not_init = 1;
 could_not_open_audio_device = 2;
 

 error_t error = 1;
 bool critical = 2;

The advantage of this is that I can use it in templates for a class that automatically detects the packet type and identifies it to give it to a registered handler, as it can be accessed via protobuf::error_message_t::packet_type to get the value.