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>

5 files changed, 28 insertions, 25 deletions

diff --git a/src/corelib/io/qiodevice.cpp b/src/corelib/io/qiodevice.cpp
index f1c42c9bb5..35911934df 100644
--- a/src/corelib/io/qiodevice.cpp
+++ b/src/corelib/io/qiodevice.cpp
@@ -1667,6 +1667,23 @@ QString QIODevice::errorString() const
     \sa read(), write()
 */
 
+/*!
+  \internal
+  \fn int qt_subtract_from_timeout(int timeout, int elapsed)
+
+  Reduces the \a timeout by \a elapsed, taking into account that -1 is a
+  special value for timeouts.
+*/
+
+int qt_subtract_from_timeout(int timeout, int elapsed)
+{
+    if (timeout == -1)
+        return -1;
+
+    timeout = timeout - elapsed;
+    return timeout < 0 ? 0 : timeout;
+}
+
 
 #if !defined(QT_NO_DEBUG_STREAM)
 QDebug operator<<(QDebug debug, QIODevice::OpenMode modes)
diff --git a/src/corelib/io/qiodevice_p.h b/src/corelib/io/qiodevice_p.h
index d764cb0fbb..ddd222e9a8 100644
--- a/src/corelib/io/qiodevice_p.h
+++ b/src/corelib/io/qiodevice_p.h
@@ -60,6 +60,8 @@ QT_BEGIN_NAMESPACE
 #define QIODEVICE_BUFFERSIZE Q_INT64_C(16384)
 #endif
 
+Q_CORE_EXPORT int qt_subtract_from_timeout(int timeout, int elapsed);
+
 // This is QIODevice's read buffer, optimized for read(), isEmpty() and getChar()
 class QIODevicePrivateLinearBuffer
 {
diff --git a/src/corelib/io/qprocess.cpp b/src/corelib/io/qprocess.cpp
index 94912ad616..baba9a0f9e 100644
--- a/src/corelib/io/qprocess.cpp
+++ b/src/corelib/io/qprocess.cpp
@@ -1793,8 +1793,7 @@ bool QProcess::waitForBytesWritten(int msecs)
         bool started = waitForStarted(msecs);
         if (!started)
             return false;
-        if (msecs != -1)
-            msecs -= stopWatch.elapsed();
+        msecs = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
     }
 
     return d->waitForBytesWritten(msecs);
@@ -1830,8 +1829,7 @@ bool QProcess::waitForFinished(int msecs)
         bool started = waitForStarted(msecs);
         if (!started)
             return false;
-        if (msecs != -1)
-            msecs -= stopWatch.elapsed();
+        msecs = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
     }
 
     return d->waitForFinished(msecs);
diff --git a/src/corelib/io/qprocess_unix.cpp b/src/corelib/io/qprocess_unix.cpp
index cc154cfbc5..1c1c058c7a 100644
--- a/src/corelib/io/qprocess_unix.cpp
+++ b/src/corelib/io/qprocess_unix.cpp
@@ -1019,19 +1019,6 @@ void QProcessPrivate::killProcess()
         ::kill(pid_t(pid), SIGKILL);
 }
 
-/*
-   Returns the difference between msecs and elapsed. If msecs is -1,
-   however, -1 is returned.
-*/
-static int qt_timeout_value(int msecs, int elapsed)
-{
-    if (msecs == -1)
-        return -1;
-
-    int timeout = msecs - elapsed;
-    return timeout < 0 ? 0 : timeout;
-}
-
 bool QProcessPrivate::waitForStarted(int msecs)
 {
     Q_Q(QProcess);
@@ -1106,7 +1093,7 @@ bool QProcessPrivate::waitForReadyRead(int msecs)
         if (!stdinChannel.buffer.isEmpty() && stdinChannel.pipe[1] != -1)
             add_fd(nfds, stdinChannel.pipe[1], &fdwrite);
 
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
 #ifdef Q_OS_BLACKBERRY
         int ret = bb_select(notifiers, nfds + 1, &fdread, &fdwrite, timeout);
 #else
@@ -1187,7 +1174,7 @@ bool QProcessPrivate::waitForBytesWritten(int msecs)
         if (!stdinChannel.buffer.isEmpty() && stdinChannel.pipe[1] != -1)
             add_fd(nfds, stdinChannel.pipe[1], &fdwrite);
 
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
 #ifdef Q_OS_BLACKBERRY
         int ret = bb_select(notifiers, nfds + 1, &fdread, &fdwrite, timeout);
 #else
@@ -1262,7 +1249,7 @@ bool QProcessPrivate::waitForFinished(int msecs)
         if (!stdinChannel.buffer.isEmpty() && stdinChannel.pipe[1] != -1)
             add_fd(nfds, stdinChannel.pipe[1], &fdwrite);
 
-        int timeout = qt_timeout_value(msecs, stopWatch.elapsed());
+        int timeout = qt_subtract_from_timeout(msecs, stopWatch.elapsed());
 #ifdef Q_OS_BLACKBERRY
         int ret = bb_select(notifiers, nfds + 1, &fdread, &fdwrite, timeout);
 #else
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;
     }
 }