Want to use a nested way to define the message is as follows:
The message A
{
The required B B;
The required C C;
}

The message B
{
The required int32 x;
The required int32 y;
}
The message C
{
The required int32 e;
The required int32 f;
}

Generated by the C + + file, finally wrote Reader and Writer to write and read the class A of attribute values, how to give the class A C type object assignment and C type in how to read out the value of the object, an excuse for their API is what?