QWinOverlappedIoNotifier: multiple I/O operations on the same handle

When doing multiple I/O operations on the same handle, we get notified
for every operations. These must be distinguished by comparing the
pointer to the OVERLAPPED struct.

We now pass the OVERLAPPED pointer via the notified signal and let the
receiver decide if it wants to handle this notification.

Change-Id: I4efe70f39c6ae5282b949f2f4b21f6e7dd3df785
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>

1 files changed, 38 insertions, 23 deletions

diff --git a/src/corelib/io/qwinoverlappedionotifier.cpp b/src/corelib/io/qwinoverlappedionotifier.cpp
index 0c698c6e53..c084912897 100644
--- a/src/corelib/io/qwinoverlappedionotifier.cpp
+++ b/src/corelib/io/qwinoverlappedionotifier.cpp
@@ -62,7 +62,8 @@ QT_BEGIN_NAMESPACE
     Once you have obtained a file handle, you can use setHandle() to get
     notifications for I/O operations. Whenever an I/O operation completes,
     the notified() signal is emitted which will pass the number of transferred
-    bytes and the operation's error code to the receiver.
+    bytes, the operation's error code and a pointer to the operation's
+    OVERLAPPED object to the receiver.
 
     Every handle that supports overlapped I/O can be used by
     QWinOverlappedIoNotifier. That includes file handles, TCP sockets
@@ -149,7 +150,7 @@ protected:
             QWinOverlappedIoNotifier *notifier = reinterpret_cast<QWinOverlappedIoNotifier *>(pulCompletionKey);
             mutex.lock();
             if (notifiers.contains(notifier))
-                notifier->notify(dwBytesRead, errorCode);
+                notifier->notify(dwBytesRead, errorCode, overlapped);
             mutex.unlock();
         }
     }
@@ -164,11 +165,10 @@ Q_GLOBAL_STATIC(QWinIoCompletionPort, iocp)
 
 QWinOverlappedIoNotifier::QWinOverlappedIoNotifier(QObject *parent)
     : QObject(parent),
-      hHandle(INVALID_HANDLE_VALUE),
-      lastNumberOfBytes(0),
-      lastErrorCode(ERROR_SUCCESS)
+      hHandle(INVALID_HANDLE_VALUE)
 {
-    hEvent = CreateEvent(NULL, TRUE, FALSE, NULL);
+    hSemaphore = CreateSemaphore(NULL, 0, 255, NULL);
+    hResultsMutex = CreateMutex(NULL, FALSE, NULL);
     connect(this, &QWinOverlappedIoNotifier::_q_notify,
             this, &QWinOverlappedIoNotifier::_q_notified, Qt::QueuedConnection);
 }
@@ -176,7 +176,8 @@ QWinOverlappedIoNotifier::QWinOverlappedIoNotifier(QObject *parent)
 QWinOverlappedIoNotifier::~QWinOverlappedIoNotifier()
 {
     setEnabled(false);
-    CloseHandle(hEvent);
+    CloseHandle(hResultsMutex);
+    CloseHandle(hSemaphore);
 }
 
 void QWinOverlappedIoNotifier::setHandle(HANDLE h)
@@ -192,15 +193,24 @@ void QWinOverlappedIoNotifier::setEnabled(bool enabled)
         iocp()->unregisterNotifier(this);
 }
 
-bool QWinOverlappedIoNotifier::waitForNotified(int msecs)
+/*!
+ * Wait synchronously for the notified signal.
+ *
+ * \returns true, if the notified signal was emitted for the I/O operation
+ *          that corresponds to the OVERLAPPED object.
+ */
+bool QWinOverlappedIoNotifier::waitForNotified(int msecs, OVERLAPPED *overlapped)
 {
-    DWORD result = WaitForSingleObject(hEvent, msecs == -1 ? INFINITE : DWORD(msecs));
-    switch (result) {
-    case WAIT_OBJECT_0:
-        _q_notified();
-        return true;
-    case WAIT_TIMEOUT:
-        return false;
+    forever {
+        DWORD result = WaitForSingleObject(hSemaphore, msecs == -1 ? INFINITE : DWORD(msecs));
+        if (result == WAIT_OBJECT_0) {
+            ReleaseSemaphore(hSemaphore, 1, NULL);
+            if (_q_notified() == overlapped)
+                return true;
+            continue;
+        } else if (result == WAIT_TIMEOUT) {
+            return false;
+        }
     }
 
     qErrnoWarning("QWinOverlappedIoNotifier::waitForNotified: WaitForSingleObject failed.");
@@ -210,20 +220,25 @@ bool QWinOverlappedIoNotifier::waitForNotified(int msecs)
 /*!
   * Note: This function runs in the I/O completion port thread.
   */
-void QWinOverlappedIoNotifier::notify(DWORD numberOfBytes, DWORD errorCode)
+void QWinOverlappedIoNotifier::notify(DWORD numberOfBytes, DWORD errorCode, OVERLAPPED *overlapped)
 {
-    lastNumberOfBytes = numberOfBytes;
-    lastErrorCode = errorCode;
-    SetEvent(hEvent);
+    WaitForSingleObject(hResultsMutex, INFINITE);
+    results.enqueue(IOResult(numberOfBytes, errorCode, overlapped));
+    ReleaseMutex(hResultsMutex);
+    ReleaseSemaphore(hSemaphore, 1, NULL);
     emit _q_notify();
 }
 
-void QWinOverlappedIoNotifier::_q_notified()
+OVERLAPPED *QWinOverlappedIoNotifier::_q_notified()
 {
-    if (WaitForSingleObject(hEvent, 0) == WAIT_OBJECT_0) {
-        ResetEvent(hEvent);
-        emit notified(lastNumberOfBytes, lastErrorCode);
+    if (WaitForSingleObject(hSemaphore, 0) == WAIT_OBJECT_0) {
+        WaitForSingleObject(hResultsMutex, INFINITE);
+        IOResult ioresult = results.dequeue();
+        ReleaseMutex(hResultsMutex);
+        emit notified(ioresult.numberOfBytes, ioresult.errorCode, ioresult.overlapped);
+        return ioresult.overlapped;
     }
+    return 0;
 }
 
 QT_END_NAMESPACE