QWinOverlappedIoNotifier: Add an extended waitForAnyNotified() method

The existing waitForNotified method has the design limitation that it
doesn't allow the tracking of multiple I/O operations on a single
file handle.

Therefore we introduce an additional method waitForAnyNotified that
returns a pointer to the triggered OVERLAPPED object.

Change-Id: I536ed7f6828daa2b0ce03f2d662eeb10aa89ca99
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/corelib/io/qwinoverlappedionotifier.cpp

@@ -41,6 +41,7 @@
 
 #include "qwinoverlappedionotifier_p.h"
 #include <qdebug.h>
+#include <qelapsedtimer.h>
 #include <qmutex.h>
 #include <qpointer.h>
 #include <qqueue.h>
@@ -292,6 +293,36 @@ void QWinOverlappedIoNotifier::setEnabled(bool enabled)
         d->iocp->unregisterNotifier(d);
 }
 
+/*!
+ * Wait synchronously for any notified signal.
+ *
+ * The function returns a pointer to the OVERLAPPED object corresponding to the completed I/O
+ * operation. In case no I/O operation was completed during the \a msec timeout, this function
+ * returns a null pointer.
+ */
+OVERLAPPED *QWinOverlappedIoNotifier::waitForAnyNotified(int msecs)
+{
+    Q_D(QWinOverlappedIoNotifier);
+    if (!d->iocp->isRunning()) {
+        qWarning("Called QWinOverlappedIoNotifier::waitForAnyNotified on inactive notifier.");
+        return 0;
+    }
+
+    if (msecs == 0)
+        d->iocp->drainQueue();
+
+    switch (WaitForSingleObject(d->hSemaphore, msecs == -1 ? INFINITE : DWORD(msecs))) {
+    case WAIT_OBJECT_0:
+        ReleaseSemaphore(d->hSemaphore, 1, NULL);
+        return d->_q_notified();
+    case WAIT_TIMEOUT:
+        return 0;
+    default:
+        qErrnoWarning("QWinOverlappedIoNotifier::waitForAnyNotified: WaitForSingleObject failed.");
+        return 0;
+    }
+}
+
 /*!
  * Wait synchronously for the notified signal.
  *
@@ -300,28 +331,21 @@ void QWinOverlappedIoNotifier::setEnabled(bool enabled)
  */
 bool QWinOverlappedIoNotifier::waitForNotified(int msecs, OVERLAPPED *overlapped)
 {
-    Q_D(QWinOverlappedIoNotifier);
-    if (!d->iocp->isRunning()) {
-        qWarning("Called QWinOverlappedIoNotifier::waitForNotified on inactive notifier.");
-        return false;
-    }
-
+    int t = msecs;
+    QElapsedTimer stopWatch;
+    stopWatch.start();
     forever {
-        if (msecs == 0)
-            d->iocp->drainQueue();
-        DWORD result = WaitForSingleObject(d->hSemaphore, msecs == -1 ? INFINITE : DWORD(msecs));
-        if (result == WAIT_OBJECT_0) {
-            ReleaseSemaphore(d->hSemaphore, 1, NULL);
-            if (d->_q_notified() == overlapped)
+        OVERLAPPED *triggeredOverlapped = waitForAnyNotified(t);
+        if (!triggeredOverlapped)
+            return false;
+        if (triggeredOverlapped == overlapped)
             return true;
-            continue;
-        } else if (result == WAIT_TIMEOUT) {
+        if (msecs != -1) {
+            t = msecs - stopWatch.elapsed();
+            if (t < 0)
                 return false;
         }
     }
-
-    qErrnoWarning("QWinOverlappedIoNotifier::waitForNotified: WaitForSingleObject failed.");
-    return false;
 }
 
 /*!

src/corelib/io/qwinoverlappedionotifier_p.h

@@ -76,6 +76,7 @@ public:
     Qt::HANDLE handle() const;
 
     void setEnabled(bool enabled);
+    OVERLAPPED *waitForAnyNotified(int msecs);
     bool waitForNotified(int msecs, OVERLAPPED *overlapped);
 
 Q_SIGNALS:

tests/auto/corelib/io/qwinoverlappedionotifier/tst_qwinoverlappedionotifier.cpp

@@ -58,6 +58,7 @@ private slots:
     void readFile();
     void waitForNotified_data();
     void waitForNotified();
+    void waitForAnyNotified();
     void brokenPipe();
     void multipleOperations();
 
@@ -195,6 +196,45 @@ void tst_QWinOverlappedIoNotifier::waitForNotified()
     QCOMPARE(notifier.waitForNotified(100, &overlapped), false);
 }
 
+void tst_QWinOverlappedIoNotifier::waitForAnyNotified()
+{
+    const QString fileName = QDir::toNativeSeparators(sourceFileInfo.absoluteFilePath());
+    const int readBufferSize = sourceFileInfo.size();
+
+    QWinOverlappedIoNotifier notifier;
+    HANDLE hFile = CreateFile(reinterpret_cast<const wchar_t*>(fileName.utf16()),
+                              GENERIC_READ, FILE_SHARE_READ,
+                              NULL, OPEN_EXISTING, FILE_FLAG_OVERLAPPED, NULL);
+    notifier.setHandle(hFile);
+    notifier.setEnabled(true);
+    QVERIFY(notifier.waitForAnyNotified(100) == 0);
+
+    OVERLAPPED overlapped1;
+    ZeroMemory(&overlapped1, sizeof(OVERLAPPED));
+    QByteArray buffer1(readBufferSize, 0);
+    BOOL readSuccess = ReadFile(hFile, buffer1.data(), buffer1.size(), NULL, &overlapped1);
+    QVERIFY(readSuccess || GetLastError() == ERROR_IO_PENDING);
+
+    OVERLAPPED overlapped2;
+    ZeroMemory(&overlapped2, sizeof(OVERLAPPED));
+    QByteArray buffer2(readBufferSize, 0);
+    readSuccess = ReadFile(hFile, buffer2.data(), buffer2.size(), NULL, &overlapped2);
+    QVERIFY(readSuccess || GetLastError() == ERROR_IO_PENDING);
+
+    QSet<OVERLAPPED *> overlappedObjects;
+    overlappedObjects << &overlapped1 << &overlapped2;
+
+    for (int i = 1; i <= 2; ++i) {
+        OVERLAPPED *notifiedOverlapped = notifier.waitForAnyNotified(3000);
+        QVERIFY(overlappedObjects.contains(notifiedOverlapped));
+        overlappedObjects.remove(notifiedOverlapped);
+    }
+
+    CloseHandle(hFile);
+    QVERIFY(overlappedObjects.isEmpty());
+    QVERIFY(notifier.waitForAnyNotified(100) == 0);
+}
+
 void tst_QWinOverlappedIoNotifier::brokenPipe()
 {
     QWinOverlappedIoNotifier notifier;