IO#getch

static VALUE
console_getch(int argc, VALUE *argv, VALUE io)
{
    rawmode_arg_t opts, *optp = rawmode_opt(&argc, argv, 0, 0, &opts);
#ifndef _WIN32
    return ttymode(io, getc_call, io, set_rawmode, optp);
#else
    rb_io_t *fptr;
    VALUE str;
    wint_t c;
    int len;
    char buf[8];
    wint_t wbuf[2];
# ifndef HAVE_RB_IO_WAIT
    struct timeval *to = NULL, tv;
# else
    VALUE timeout = Qnil;
# endif

    GetOpenFile(io, fptr);
    if (optp) {
        if (optp->vtime) {
# ifndef HAVE_RB_IO_WAIT
            to = &tv;
# else
            struct timeval tv;
# endif
            tv.tv_sec = optp->vtime / 10;
            tv.tv_usec = (optp->vtime % 10) * 100000;
# ifdef HAVE_RB_IO_WAIT
            timeout = rb_fiber_scheduler_make_timeout(&tv);
# endif
        }
        switch (optp->vmin) {
          case 1: /* default */
            break;
          case 0: /* return nil when timed out */
            if (optp->vtime) break;
            /* fallthru */
          default:
            rb_warning("min option larger than 1 ignored");
        }
        if (optp->intr) {
# ifndef HAVE_RB_IO_WAIT
            int w = rb_wait_for_single_fd(fptr->fd, RB_WAITFD_IN, to);
            if (w < 0) rb_eof_error();
            if (!(w & RB_WAITFD_IN)) return Qnil;
# else
            VALUE result = rb_io_wait(io, RB_INT2NUM(RUBY_IO_READABLE), timeout);
            if (!RTEST(result)) return Qnil;
# endif
        }
        else if (optp->vtime) {
            rb_warning("Non-zero vtime option ignored if intr flag is unset");
        }
    }
    len = (int)(VALUE)rb_thread_call_without_gvl(nogvl_getch, wbuf, RUBY_UBF_IO, 0);
    switch (len) {
      case 0:
        return Qnil;
      case 2:
        buf[0] = (char)wbuf[0];
        c = wbuf[1];
        len = 1;
        do {
            buf[len++] = (unsigned char)c;
        } while ((c >>= CHAR_BIT) && len < (int)sizeof(buf));
        return rb_str_new(buf, len);
      default:
        c = wbuf[0];
        len = rb_uv_to_utf8(buf, c);
        str = rb_utf8_str_new(buf, len);
        return rb_str_conv_enc(str, NULL, rb_default_external_encoding());
    }
#endif
}