[newlib-cygwin] Cygwin: console: Add support for FLUSHO and Ctrl-O.

[Corinna Vinschen <corinna@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=b56a371436192c965984013682043412cb22fc57

commit b56a371436192c965984013682043412cb22fc57
Author: Takashi Yano via Cygwin-patches <cygwin-patches@cygwin.com>
Date:   Fri Feb 19 17:44:02 2021 +0900

    Cygwin: console: Add support for FLUSHO and Ctrl-O.
    
    - With this patch, FLUSHO and Ctrl-O (VDISCARD) get working.

Diff:
---
 winsup/cygwin/fhandler_console.cc | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index ca8eb6400..6ded9eabf 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -259,6 +259,7 @@ fhandler_console::cons_master_thread (handle_set_t *p, tty *ttyp)
 		    {
 		      ttyp->kill_pgrp (sig);
 		      ttyp->output_stopped = false;
+		      ti.c_lflag &= ~FLUSHO;
 		      /* Discard type ahead input */
 		      goto skip_writeback;
 		    }
@@ -286,6 +287,13 @@ fhandler_console::cons_master_thread (handle_set_t *p, tty *ttyp)
 			   && c && i >= output_stopped_at)
 		    goto restart_output;
 		}
+	      if ((ti.c_lflag & ICANON) && (ti.c_lflag & IEXTEN)
+		  && CCEQ (ti.c_cc[VDISCARD], c))
+		{
+		  if (input_rec[i].Event.KeyEvent.bKeyDown)
+		    ti.c_lflag ^= FLUSHO;
+		  processed = true;
+		}
 	      break;
 	    case WINDOW_BUFFER_SIZE_EVENT:
 	      SHORT y = con.dwWinSize.Y;
@@ -3052,6 +3060,9 @@ fhandler_console::write (const void *vsrc, size_t len)
   if (bg <= bg_eof)
     return (ssize_t) bg;
 
+  if (get_ttyp ()->ti.c_lflag & FLUSHO)
+    return len; /* Discard write data */
+
   if (get_ttyp ()->output_stopped && is_nonblocking ())
     {
       set_errno (EAGAIN);