Introduce qt_subtract_from_timeout to reduce code duplication.

The same qt_timeout_value function was copied 5 times in qtbase's code,
so provide a common implementation in QIoDevice that can be used by
everyone.

This commit also corrects the remaining time calculation in
QProcess::waitForBytesWritten and QProcess::waitForFinished by using
this new function.

For QProcess::waitForFinished, if the process started within almost exactly
the timeout time passed to waitForFinished, msecs - stopWatch.elapsed() would
be -1, which is a special value.

Change-Id: I7b76ee6bae695eafdd02e3db03e2ff1e23a7f40c
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

1 files changed, 4 insertions, 5 deletions

diff --git a/src/corelib/io/qwinoverlappedionotifier.cpp b/src/corelib/io/qwinoverlappedionotifier.cpp
index de0e205d26..7a005430ea 100644
--- a/src/corelib/io/qwinoverlappedionotifier.cpp
+++ b/src/corelib/io/qwinoverlappedionotifier.cpp
@@ -41,6 +41,7 @@
 #include <qthread.h>
 #include <qt_windows.h>
 #include <private/qobject_p.h>
+#include <private/qiodevice_p.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -332,11 +333,9 @@ bool QWinOverlappedIoNotifier::waitForNotified(int msecs, OVERLAPPED *overlapped
             return false;
         if (triggeredOverlapped == overlapped)
             return true;
-        if (msecs != -1) {
-            t = msecs - stopWatch.elapsed();
-            if (t < 0)
-                return false;
-        }
+        msecs = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
+        if (t == 0)
+            return false;
     }
 }