Re: [PATCH 5/5 v2] keyboard input: when an unknown sequence is seen, purge all buffered input

[Denys Vlasenko <vda linux googlemail com>]

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On Thu, Oct 25, 2012 at 4:45 PM, Denys Vlasenko
<vda linux googlemail com> wrote:
> When we see an unknown sequence, it is not enough
> to drop already received part - there can be more of it
> coming over e.g. a serial line.
>
> To prevent interpreting it as a random garbage,
> eat and discard all chars that follow.
> Small, but non-zero timeout is needed to reconnect
> escape sequence split up by a serial line.
>
> Before this change, Ctrl-Alt-Shift-Right_Arrow generates "1;8C"
> bogus "input" in MC on my machine; after the change,
> nothing is generated.
>
> Signed-off-by: Denys Vlasenko <vda linux googlemail com>
> ---
>  lib/tty/key.c |   21 ++++++++++++++++-----
>  1 files changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/lib/tty/key.c b/lib/tty/key.c
> index 9b97aa8..818b2e6 100644
> --- a/lib/tty/key.c
> +++ b/lib/tty/key.c
> @@ -1216,14 +1216,14 @@ correct_key_code (int code)
>  /* --------------------------------------------------------------------------------------------- */
>
>  static int
> -xgetch_second (void)
> +getch_with_timeout (unsigned delay_us)
>  {
>      fd_set Read_FD_Set;
>      int c;
>      struct timeval time_out;
>
> -    time_out.tv_sec = old_esc_mode_timeout / 1000000;
> -    time_out.tv_usec = old_esc_mode_timeout % 1000000;
> +    time_out.tv_sec = delay_us / 1000000u;
> +    time_out.tv_usec = delay_us % 1000000u;
>      tty_nodelay (TRUE);
>      FD_ZERO (&Read_FD_Set);
>      FD_SET (input_fd, &Read_FD_Set);
> @@ -1891,7 +1891,18 @@ get_key_code (int no_delay)
>                      seq_append = NULL;
>                  }
>                  if (bad_seq)
> +                {
> +                    /* This is an unknown ESC sequence.
> +                     * To prevent interpreting its tail as a random garbage,
> +                     * eat and discard all buffered and quickly following chars.
> +                     * Small, but non-zero timeout is needed to reconnect
> +                     * escape sequence split up by e.g. a serial line.
> +                     */
> +                    int paranoia = 20;
> +                    while (getch_with_timeout (old_esc_mode_timeout) >= 0 && --paranoia != 0)
> +                        continue;
>                      goto nodelay_try_again;
> +                }
>              }
>              if ((d > 127 && d < 256) && use_8th_bit_as_meta)
>              {
> @@ -2009,8 +2020,8 @@ get_key_code (int no_delay)
>                      goto nodelay_try_again;
>                  }
>                  esctime.tv_sec = -1;
> -                c = xgetch_second ();
> -                keylog (" c=xgetch_second()=%d\n", c);
> +                c = getch_with_timeout (old_esc_mode_timeout);
> +                keylog (" c=getch_with_timeout(%d)=%d\n", old_esc_mode_timeout, c);
>                  if (c == -1)
>                  {
>                      pending_keys = seq_append = NULL;
> --
> 1.7.7.6
>