How to initialize a repeated element in protocol buffer?

Question

Assume that I have this message.

message A {
  repeated float w = 1 [packed = true];
}

How can I initialize w in my Code? Can I do any better than this?

a = A()    
for (int i = 0 ; i < n; ++i) 
   a.add_w(0);

Answer 1

a.w() or a.mutable_w() will return a google::protobuf::RepeatedField<float> which provides some additional options. For instance, you could call a.mutable_w()->Reserve(n) to pre-allocate space in advance, to avoid the usual strategy of re-allocating every time the size doubles. You can also use Resize(n) followed by mutable_data() to get direct access to the underlying buffer, but this probably won't provide much speed benefit over Reserve(n) followed by your loop.