rbuf_empty, rbuf_not_empty - find out if an rbuf is holding anything
SYNOPSIS
#include <roy.h>
int rbuf_empty (RBuf *buf);
int rbuf_not_empty (RBuf *buf);
DESCRIPTION
Unlike rbuf_len(3) these two api calls do not require buf to be
non NULL. If buf is not empty the programmer can assume that buf
is non NULL and has data in it's buffer.
A call to rbuf_empty(3) returns TRUE if buf is NULL or buf's length
is zero(0) . Otherwise, FALSE is returned.
A call to rbuf_not_empty(3) returns TRUE if buf is non NULL and
buf's length is non zero(0) . Otherwise, FALSE is returned. This
call is equivalant to !rbuf_empty(3) .
