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added timed drain filter to prevent garbage input after attach #39

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added timed drain filter to prevent garbage input after attach #39

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43 changes: 43 additions & 0 deletions attach.c
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Original file line number Diff line number Diff line change
Expand Up @@ -366,6 +366,49 @@ int attach_main(int noerror)
cur_term.c_cc[VTIME] = 0;
tcsetattr(0, TCSADRAIN, &cur_term);

/* Drain: now that we are in raw mode, swallow any terminal
* responses provoked by the on-disk log replay. We do this
* BEFORE sending MSG_ATTACH / MSG_REDRAW so that the running
* program's own query/response cycle (e.g. fish prompts after
* SIGWINCH) flows through normally and is never swallowed.
* Default 100ms; override with ATCH_DRAIN_MS, 0 to disable. */
{
int drain_ms = 100;
const char *env_drain = getenv("ATCH_DRAIN_MS");
if (env_drain)
drain_ms = atoi(env_drain);
if (drain_ms > 0) {
struct timeval deadline, now;
fd_set drfds;
unsigned char junk[256];

gettimeofday(&deadline, NULL);
deadline.tv_usec += (long)(drain_ms % 1000) * 1000;
deadline.tv_sec += drain_ms / 1000;
if (deadline.tv_usec >= 1000000) {
deadline.tv_sec++;
deadline.tv_usec -= 1000000;
}
for (;;) {
struct timeval tv;
long usec_left;

gettimeofday(&now, NULL);
usec_left =
(deadline.tv_sec - now.tv_sec) * 1000000 +
(deadline.tv_usec - now.tv_usec);
if (usec_left <= 0)
break;
tv.tv_sec = usec_left / 1000000;
tv.tv_usec = usec_left % 1000000;
FD_ZERO(&drfds);
FD_SET(0, &drfds);
if (select(1, &drfds, NULL, NULL, &tv) > 0)
(void)read(0, junk, sizeof(junk));
}
}
}

/* Clear the screen on attach. Only do a full reset when explicitly
** requested (CLEAR_MOVE); default/unspec just emits a blank line so
** any preceding log replay remains visible.
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