As stated by previous posts (the uint16 one in particular), protobuf C+
+ is not designed for extremely-memory-constrained systems. I was
curious about the decision to not make the "bare bones" structure of
the message public and provide a way to construct one from another.
For example right now the generated code looks something like this:
couch.proto:
message Couch
{
required uint32 width;
required uint32 length;
}
couch.pb.h:
class Couch : public ::google::protobuf::Message {
public:
Couch();
// rest of public interface...
private:
// pb data members
uint32 width_;
uint32 length_;
// more pb data member
};
If pb provided a "bare bones" structure it might look something like:
couch.pb.h:
class Couch : public ::google::protobuf::Message {
public:
struct Lite {
Lite(const Couch& from);
uint32 width_;
uint32 length_;
};
Couch();
Couch(const Couch::Lite& from);
// rest of public interface...
private:
// pb data members
Lite impl_;
// more pb data member
};
First off, the API for constructing one from another is more just to
show an example than anything else. Exposing the underlying structure
allows you to store smaller in-memory copies of the message. This
comes into play more when the structure is part of a larger class that
isn't going across the wire.
class LivingRoom {
Couch::Lite couches[10];
};
class Apartment{
LivingRoom rooms[3];
};
class Complex {
Apartment apartments[10000];
};
class City {
Complex complexes[100000];
}
It seems wasteful to have Couch when you could just as well have
Couch::Lite. With a change like this, if you aren't as concerned with
memory usage, there is no change to how pb behaves or how you use
it.
Shaun
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