QNetworkReply: replace a QQueue with a std::vector

The 'queue' was never used as a queue: it was populated, and then
exchanged into a local copy to be consumed in a loop. This loop used
dequeue(), but of course it could just const-iterate the container and
dump it as the end, since the member variable was already reset at
that point, no-one could tell the difference from the outside.

So, no need for a queue. A vector will do very nicely.

The loop now uses ranged-for and qExchange(), greatly simplifying the
code over the old version.

Add another qExchange() call as a drive-by.

Change-Id: I6147453dc9edfe9500833627b123bb3a31114651
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

2 files changed, 9 insertions, 16 deletions

diff --git a/src/network/access/qnetworkreplyimpl.cpp b/src/network/access/qnetworkreplyimpl.cpp
index 1a02938de9..6eab500e8c 100644
--- a/src/network/access/qnetworkreplyimpl.cpp
+++ b/src/network/access/qnetworkreplyimpl.cpp
@@ -158,7 +158,7 @@ void QNetworkReplyImplPrivate::_q_startOperation()
     } else {
         if (state != Finished) {
             if (operation == QNetworkAccessManager::GetOperation)
-                pendingNotifications.append(NotifyDownstreamReadyWrite);
+                pendingNotifications.push_back(NotifyDownstreamReadyWrite);
 
             handleNotifications();
         }
@@ -433,8 +433,9 @@ void QNetworkReplyImplPrivate::setup(QNetworkAccessManager::Operation op, const
 void QNetworkReplyImplPrivate::backendNotify(InternalNotifications notification)
 {
     Q_Q(QNetworkReplyImpl);
-    if (!pendingNotifications.contains(notification))
-        pendingNotifications.enqueue(notification);
+    const auto it = std::find(pendingNotifications.cbegin(), pendingNotifications.cend(), notification);
+    if (it == pendingNotifications.cend())
+        pendingNotifications.push_back(notification);
 
     if (pendingNotifications.size() == 1)
         QCoreApplication::postEvent(q, new QEvent(QEvent::NetworkReplyUpdated));
@@ -445,14 +446,9 @@ void QNetworkReplyImplPrivate::handleNotifications()
     if (notificationHandlingPaused)
         return;
 
-    NotificationQueue current = pendingNotifications;
-    pendingNotifications.clear();
-
-    if (state != Working)
-        return;
-
-    while (state == Working && !current.isEmpty()) {
-        InternalNotifications notification = current.dequeue();
+     for (InternalNotifications notification : qExchange(pendingNotifications, {})) {
+        if (state != Working)
+            return;
         switch (notification) {
         case NotifyDownstreamReadyWrite:
             if (copyDevice)
@@ -466,8 +462,7 @@ void QNetworkReplyImplPrivate::handleNotifications()
             break;
 
         case NotifyCopyFinished: {
-            QIODevice *dev = copyDevice;
-            copyDevice = 0;
+            QIODevice *dev = qExchange(copyDevice, nullptr);
             backend->copyFinished(dev);
             break;
         }
diff --git a/src/network/access/qnetworkreplyimpl_p.h b/src/network/access/qnetworkreplyimpl_p.h
index 85f5b862a8..8cec79541a 100644
--- a/src/network/access/qnetworkreplyimpl_p.h
+++ b/src/network/access/qnetworkreplyimpl_p.h
@@ -117,8 +117,6 @@ public:
         NotifyCopyFinished
     };
 
-    typedef QQueue<InternalNotifications> NotificationQueue;
-
     QNetworkReplyImplPrivate();
 
     void _q_startOperation();
@@ -178,7 +176,7 @@ public:
     bool cacheEnabled;
     QIODevice *cacheSaveDevice;
 
-    NotificationQueue pendingNotifications;
+    std::vector<InternalNotifications> pendingNotifications;
     bool notificationHandlingPaused;
 
     QUrl urlForLastAuthentication;