通过TCP套接字编码和发送XDR结构（C-Linux）

Question

I have to ask the question below:

I have to send the following XDR message:

struct Responde{
 float numbers<>;
 bool end;
}

I know how to enconde array (xdr_array) and bool (xdr_bool) but how can I:

1) Encode the struct? 2) Send the struct over a socket?

Thanks to all, but I don't know XDR and I have to use it. Thanks again.

Nb: How title shows I refer to C language and Linux environment.

Answer 1

The most flexible solution would of course be to use the rpcgen tool to compile the XDR definition to C code, which you can then compile and used in your C application. But if you do not want introduce this dependency into your project, you can of course write the serialization code by hand.

RFC 1831 will give you a detailed description of how such a structure is serialize but here is what you need to know for your example:

• All number in XDR are encoded in big-endian order.
• All fields in a structure are aligned to 4 bytes and the fields are concatenated in the order they are declared.
• A float encodes a number as a 32-bit floating point number.
• The variable length array of floats is encoded as a 32-bit integer with containing the number of elements followed by the float numbers.
• A bool encodes a boolean value as a 32-bit integer where a true value is encoded as the number 1 and a false value is encoded as the number 0 .

For example, if your struct was filled with 3 floats and the value true, you would get the following byte stream:

00 00 00 03  xx xx xx xx  yy yy yy yy  zz zz zz zz  00 00 00 01

Where the sequences of x , y and z are the floating point numbers.