From: Takashi Yano <takashi.yano@nifty.ne.jp>
To: cygwin-patches@cygwin.com
Subject: [PATCH] Cygwin: console: Fix typeahead key swapping which still occurs.
Date: Fri, 18 Mar 2022 22:42:34 +0900 [thread overview]
Message-ID: <20220318134234.311-1-takashi.yano@nifty.ne.jp> (raw)
- The commit "Cygwin: console: Improve the code to avoid typeahead
key swapping." did not solve the problem enough. Two unexpected
things happen.
(1) wVirtualKeyCode and wVirtualScanCode of readback key event may
be null'ed even if they are not zero on WriteConsoleInputW().
Therefore, memcmp() may report the event sequence is not equal.
(2) WriteConsoleInputW() may not be atomic. The event sequence
which is written by WriteConsoleInputW() may be inserted by
key input in the middle of the sequence. Current code gives
up to fix in this situation.
This patch should fix that issue.
---
winsup/cygwin/fhandler_console.cc | 58 ++++++++++++++++++++-----------
1 file changed, 38 insertions(+), 20 deletions(-)
diff --git a/winsup/cygwin/fhandler_console.cc b/winsup/cygwin/fhandler_console.cc
index 241ca48ea..b92d758d1 100644
--- a/winsup/cygwin/fhandler_console.cc
+++ b/winsup/cygwin/fhandler_console.cc
@@ -180,6 +180,29 @@ cons_master_thread (VOID *arg)
return 0;
}
+/* Compare two INPUT_RECORD sequences */
+static inline bool
+inrec_eq (const INPUT_RECORD *a, const INPUT_RECORD *b, DWORD n)
+{
+ for (DWORD i = 0; i < n; i++)
+ {
+ if (a[i].EventType == KEY_EVENT && b[i].EventType == KEY_EVENT)
+ { /* wVirtualKeyCode and wVirtualScanCode of the readback
+ key event may be different from that of written event. */
+ const KEY_EVENT_RECORD *ak = &a[i].Event.KeyEvent;
+ const KEY_EVENT_RECORD *bk = &b[i].Event.KeyEvent;
+ if (ak->bKeyDown != bk->bKeyDown
+ || ak->uChar.UnicodeChar != bk->uChar.UnicodeChar
+ || ak->dwControlKeyState != bk->dwControlKeyState
+ || ak->wRepeatCount != bk->wRepeatCount)
+ return false;
+ }
+ else if (memcmp (a + i, b + i, sizeof (INPUT_RECORD)) != 0)
+ return false;
+ }
+ return true;
+}
+
/* This thread processes signals derived from input messages.
Without this thread, those signals can be handled only when
the process calls read() or select(). This thread reads input
@@ -328,30 +351,25 @@ remove_record:
if (n < total_read)
break; /* Someone has read input without acquiring
input_mutex. ConEmu cygwin-connector? */
- if (memcmp (input_rec, tmp, m::bytes (total_read)) == 0)
+ if (inrec_eq (input_rec, tmp, total_read))
break; /* OK */
/* Try to fix */
- DWORD incr = n - total_read;
- DWORD ofst;
- for (ofst = 1; ofst <= incr; ofst++)
- if (memcmp (input_rec, tmp + ofst, m::bytes (total_read)) == 0)
+ acquire_attach_mutex (mutex_timeout);
+ ReadConsoleInputW (p->input_handle, tmp, inrec_size, &n);
+ release_attach_mutex ();
+ for (DWORD i = 0, j = 0; j < n; j++)
+ if (i == total_read || !inrec_eq (input_rec + i, tmp + j, 1))
{
- acquire_attach_mutex (mutex_timeout);
- ReadConsoleInputW (p->input_handle, tmp, inrec_size, &n);
- release_attach_mutex ();
- memcpy (input_rec, tmp + ofst, m::bytes (total_read));
- memcpy (input_rec + total_read, tmp, m::bytes (ofst));
- if (n > ofst + total_read)
- memcpy (input_rec + total_read + ofst,
- tmp + ofst + total_read,
- m::bytes (n - (ofst + total_read)));
- total_read = n;
- break;
+ if (total_read + j - i >= n)
+ { /* Something is wrong. Giving up. */
+ WriteConsoleInputW (p->input_handle, tmp, n, &n);
+ goto skip_writeback;
+ }
+ input_rec[total_read + j - i] = tmp[j];
}
- if (ofst > incr)
- break; /* Writeback was not atomic. Or someone has read
- input without acquiring input_mutex.
- Giving up because hard to fix. */
+ else
+ i++;
+ total_read = n;
}
while (true);
}
--
2.35.1
reply other threads:[~2022-03-18 13:43 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20220318134234.311-1-takashi.yano@nifty.ne.jp \
--to=takashi.yano@nifty.ne.jp \
--cc=cygwin-patches@cygwin.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).