read_nonblock

/*
 *  call-seq:
 *     ios.read_nonblock(maxlen)              => string
 *     ios.read_nonblock(maxlen, outbuf)      => outbuf
 *
 *  Reads at most <i>maxlen</i> bytes from <em>ios</em> using
 *  read(2) system call after O_NONBLOCK is set for
 *  the underlying file descriptor.
 *
 *  If the optional <i>outbuf</i> argument is present,
 *  it must reference a String, which will receive the data.
 *
 *  read_nonblock just calls read(2).
 *  It causes all errors read(2) causes: EAGAIN, EINTR, etc.
 *  The caller should care such errors.
 *
 *  read_nonblock causes EOFError on EOF.
 *
 *  If the read buffer is not empty,
 *  read_nonblock reads from the buffer like readpartial.
 *  In this case, read(2) is not called.
 *
 */

static VALUE
io_read_nonblock(int argc, VALUE *argv, VALUE io)
{
    VALUE ret;

    ret = io_getpartial(argc, argv, io, 1);
    if (NIL_P(ret))
        rb_eof_error();
    else
        return ret;
}