Render timing.c robust in the face of strangeness. The strangenesses

[u/mdw/putty] / unix / uxplink.c

diff --git a/unix/uxplink.c b/unix/uxplink.c
index 6bc1b61..c026157 100644 (file)
--- a/unix/uxplink.c
+++ b/unix/uxplink.c
@@ -670,8 +670,27 @@ int main(int argc, char **argv)
            ret = select(maxfd, &rset, &wset, &xset, ptv);
            if (ret == 0)
                now = next;
-           else
-               now = GETTICKCOUNT();
+           else {
+               long newnow = GETTICKCOUNT();
+               /*
+                * Check to see whether the system clock has
+                * changed massively during the select.
+                */
+               if (newnow - now < 0 || newnow - now > next - now) {
+                   /*
+                    * If so, look at the elapsed time in the
+                    * select and use it to compute a new
+                    * tickcount_offset.
+                    */
+                   long othernow = now + tv.tv_sec * 1000 + tv.tv_usec / 1000;
+                   /* So we'd like GETTICKCOUNT to have returned othernow,
+                    * but instead it return newnow. Hence ... */
+                   tickcount_offset += othernow - newnow;
+                   now = othernow;
+               } else {
+                   now = newnow;
+               }
+           }
        } while (ret < 0 && errno == EINTR);
 
        if (ret < 0) {