QFuture: Wait for result on iterator advance

Wait for the result at the target index if the future
is running and the iterator index is past the current
result count.

Determine if there is a result at the target index
after waitForResult() returns, and return -1/end if
not.

Also support decrementing the end iterator. In this
case wait for the future to finish in order to get
the final result count.

Task-number: QTBUG-59811
Change-Id: I8fcc711bab2e72c3c5196a55b794d25e18bb324d
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

1 files changed, 67 insertions, 0 deletions

diff --git a/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp b/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
index b8c82c2ea0..a42454124e 100644
--- a/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
+++ b/tests/auto/corelib/thread/qfuture/tst_qfuture.cpp
@@ -49,6 +49,24 @@ struct ResultStoreInt : QtPrivate::ResultStoreBase
     ~ResultStoreInt() { clear<int>(); }
 };
 
+class LambdaThread : public QThread
+{
+public:
+    LambdaThread(std::function<void ()> fn)
+    :m_fn(fn)
+    {
+
+    }
+
+    void run() override
+    {
+        m_fn();
+    }
+
+private:
+    std::function<void ()> m_fn;
+};
+
 class tst_QFuture: public QObject
 {
     Q_OBJECT
@@ -67,6 +85,7 @@ private slots:
     void resultsAsList();
     void implicitConversions();
     void iterators();
+    void iteratorsThread();
     void pause();
     void throttling();
     void voidConversions();
@@ -1144,6 +1163,54 @@ void tst_QFuture::iterators()
         }
     }
 }
+void tst_QFuture::iteratorsThread()
+{
+    const int expectedResultCount = 10;
+    const int delay = 10;
+    QFutureInterface<int> futureInterface;
+
+    // Create result producer thread. The results are
+    // produced with delays in order to make the consumer
+    // wait.
+    QSemaphore sem;
+    LambdaThread thread = {[=, &futureInterface, &sem](){
+        for (int i = 1; i <= expectedResultCount; i += 2) {
+            int result = i;
+            futureInterface.reportResult(&result);
+            result = i + 1;
+            futureInterface.reportResult(&result);
+        }
+
+        sem.acquire(2);
+        futureInterface.reportFinished();
+    }};
+
+    futureInterface.reportStarted();
+    QFuture<int> future = futureInterface.future();
+
+    // Iterate over results while the thread is producing them.
+    thread.start();
+    int resultCount = 0;
+    int resultSum = 0;
+    for (int result : future) {
+        sem.release();
+        ++resultCount;
+        resultSum += result;
+    }
+    thread.wait();
+
+    QCOMPARE(resultCount, expectedResultCount);
+    QCOMPARE(resultSum, expectedResultCount * (expectedResultCount + 1) / 2);
+
+    // Reverse iterate
+    resultSum = 0;
+    QFutureIterator<int> it(future);
+    it.toBack();
+    while (it.hasPrevious())
+        resultSum += it.previous();
+
+    QCOMPARE(resultSum, expectedResultCount * (expectedResultCount + 1) / 2);
+}
 
 class SignalSlotObject : public QObject
 {