Repeated sub-messages in protobuf-c

Can somebody giv开发者_如何学运维e me an example of packing\unpacking message with repeating sub-message in protobuf-c?

Official documentation in empty on this matter.

message B {
  required int64 i = 1;
};

message A {
  repeated B numbers = 1;
};

A a;
a.ParseFromString(<str>)
for (int i = 0; i < a.numbers_size(); ++i) {
  const B& b = a.numbers(i);
  printf("%d\n", b.i());
}

proto:

message SubMsg {
  bytes value = 1;
}

message MainMsg {
  repeated SubMsg msgs = 1;
}

pack (do not forget to free memory (free(...)):

MainMsg mainMsg = { };
main_msg__init(&mainMsg);
SubMsg **subMsgs = calloc(LEN, sizeof(SubMsg*));
for (int i = 0; i < LEN; i++) {
    subMsgs[i] = calloc(1, sizeof(SubMsg));
    sub_msg__init(subMsgs[i]);
    subMsgs[i]->value.data = DATA;
    subMsgs[i]->value.len = DATALEN;
}
mainMsg.msgs = subMsgs;
mainMsg.n_msgs = LEN;
...
main_msg__pack(&mainMsg, BUFFER);

unpack (do not forget to free memory (..._free_unpacked(...)):

MainMsg* mainMsg = main_msg__unpack(nullptr, BUFFERLEN, BUFFER);
if (! mainMsg) {
    // error
    return;
}

SubMsg **subMsgs = mainMsg->msgs;
...

proto:

message A {
  optional uint32 key = 1;
  optional uint64 value = 2;
}

message B {
  repeated A msg = 1;
}

if have optional XXX field, try to set has_XXX true;

  B msg;  
  filebackup__heartbeat_content__init(&msg);
  A **subs = (A**)malloc(N * sizeof(A*));
  void *buf;                      
  unsigned len,i;                 
  for (int i = 0; i < N; ++i) {
    subs[i] = (A*)malloc(sizeof(A));
    filebackup__job_status__init(subs[i]);
    subs[i]->key = i + 1;
    subs[i]->has_key = 1;
    subs[i]->value = (i + 1) * 100;
    subs[i]->has_value = 1;
  }
  msg.msg = subs;
  msg.n_msg = N;
  len =  filebackup__heartbeat_content__get_packed_size(&msg);  
  buf = malloc(len);
  filebackup__heartbeat_content__pack(&msg, (uint8_t *)buf);    

"Reading A Message" section of Google's C++ tutorial has relevant sample code: http://code.google.com/apis/protocolbuffers/docs/cpptutorial.html

Also, STL's for_each also appears to work OK (syntactic sugar, more-or-less): std::for_each(a.numbers().begin() ,a.numbers().end() ,[](const B& b) { std::cout << b.i() << std::endl ; } ) ;