nread()
public
Returns number of bytes that can be read without blocking. Returns zero if no
information available.
static VALUE
io_nread(VALUE io)
{
rb_io_t *fptr;
int len;
ioctl_arg n;
GetOpenFile(io, fptr);
rb_io_check_readable(fptr);
len = rb_io_read_pending(fptr);
if (len > 0) return len;
if (!FIONREAD_POSSIBLE_P(fptr->fd)) return INT2FIX(0);
if (ioctl(fptr->fd, FIONREAD, &n)) return INT2FIX(0);
if (n > 0) return ioctl_arg2num(n);
return INT2FIX(0);
}