Hi,
I am trying to string up multiple messages of different C++ built-in
types into one message. Conceptually, it's something like:
codedstream << int_x << float_y << double_z;
I am thinking of implementing:
=====================
.proto File
=====================
enum Type
{
// Enums that correspond to
// C++ built-in types
Tint = 0;
Tdouble = 0;
Tfloat = 0;
}
Proto_int { required int val = 1; }
Proto_double { required double val = 1; }
Proto_float { required float val = 1; }
=====================
C++ code to
write built-in
types to protobuf
=====================
sos = new StringOutputStream(&buf);
out = new CodedOutputStream(&sos);
...
// We want to write all 3 of these in ONE protobuf message
double d = 123.0;
int i = 456;
float f = 789.0f;
// Create the messages
Proto_int msg_int;
Proto_double msg_double;
Proto_float msg_float;
msg_int.set_val(i);
msg_double.set_val(d);
msg_float.set_val(f);
// Write out the messages:
// 1. First, write out the size of the message ...
out->WriteVarint32(sizeof(msg_int));
// 2. then the type (so that we know how to parse it when we read
back) ...
// QUESTION: WriteVarint32 is used to write ints, what should I use
to
// write double/float?
out->WriteVarint32(Tint);
// 3. then the message itself
msg_int.SerializeToCodedStream(&out);
// Then repeat 1 - 3 for double and float, using msg_double/Tdouble
and msg_float/Tfloat respectively.
=====================
code to READ from
protobuf and reconstruct
built-in types
=====================
bool read() {
ArrayInputStream ais(static_cast<const void *>(&buf[0]), buf.size());
CodedInputStream in(&ais);
google::protobuf::uint32 type = 0;
google::protobuf::uint32 size = 0;
if (!in.ReadVarint32(&size)) return false;
while(size) {
if (!in.ReadVarint32(&type)) return false;
CodedInputStream::Limit limit = in.PushLimit(size);
switch(type) {
case Tdouble:
{
Proto_double p;
p.ParseFromCodedStream(&in);
}
break;
... similar code for Tint and Tfloat
}
=====================
Question
=====================
The above scheme feels very inefficient, and I suspect I am probably
doing it wrong.
For example, do I really need to make dummy wrappers like this:
"Proto_int { required int val = 1; }"
What is the correct way to achieve my goal stated above?
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