From d57adfe5f375121c3e233465526ee5d9df03e1e9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?M=C3=A5rten=20Nordheim?= <marten.nordheim@qt.io>
Date: Wed, 26 Feb 2020 18:06:49 +0100
Subject: QtConcurrent: filter- and map-reduce with initial value

It takes any type which is implictly covertible to the result type
and then converts it in the outer-layers. Then it passes it into the
deeper layers and initiales the result value.

One drive-by fix with a missing letter in the documentation.

[ChangeLog][QtConcurrent] QtConcurrent::mappedReduce and
QtConcurrent::filteredReduced, as well as their blocking variants,
now optionally take an initial value.

Fixes: QTBUG-73240
Change-Id: I7a80d96693cfa3374847c75c75b3167664609c1a
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
---
 src/concurrent/qtconcurrentfilterkernel.h | 44 +++++++++++++++++++++++++------
 1 file changed, 36 insertions(+), 8 deletions(-)

(limited to 'src/concurrent/qtconcurrentfilterkernel.h')

diff --git a/src/concurrent/qtconcurrentfilterkernel.h b/src/concurrent/qtconcurrentfilterkernel.h
index e921a3d51a..8ec551eeb2 100644
--- a/src/concurrent/qtconcurrentfilterkernel.h
+++ b/src/concurrent/qtconcurrentfilterkernel.h
@@ -173,14 +173,15 @@ public:
         : IterateKernelType(begin, end), reducedResult(), keep(_keep), reduce(_reduce), reducer(reduceOption)
     { }
 
-#if 0
-    FilteredReducedKernel(ReducedResultType initialValue,
-                          KeepFunctor keep,
-                          ReduceFunctor reduce,
-                          ReduceOption reduceOption)
-        : reducedResult(initialValue), keep(keep), reduce(reduce), reducer(reduceOption)
-    { }
-#endif
+    FilteredReducedKernel(Iterator begin, Iterator end, KeepFunctor _keep, ReduceFunctor _reduce,
+                          ReducedResultType &&initialValue, ReduceOptions reduceOption)
+        : IterateKernelType(begin, end),
+          reducedResult(std::forward<ReducedResultType>(initialValue)),
+          keep(_keep),
+          reduce(_reduce),
+          reducer(reduceOption)
+    {
+    }
 
     bool runIteration(Iterator it, int index, ReducedResultType *) override
     {
@@ -337,6 +338,33 @@ inline ThreadEngineStarter<ResultType> startFilteredReduced(Iterator begin, Iter
     return startThreadEngine(new FilteredReduceType(begin, end, mapFunctor, reduceFunctor, options));
 }
 
+// Repeat the two functions above, but now with an initial value!
+//! [QtConcurrent-6]
+template <typename ResultType, typename Sequence, typename MapFunctor, typename ReduceFunctor>
+inline ThreadEngineStarter<ResultType> startFilteredReduced(const Sequence & sequence,
+                                                           MapFunctor mapFunctor, ReduceFunctor reduceFunctor,
+                                                           ResultType &&initialValue,
+                                                           ReduceOptions options)
+{
+    typedef typename Sequence::const_iterator Iterator;
+    typedef ReduceKernel<ReduceFunctor, ResultType, typename qValueType<Iterator>::value_type > Reducer;
+    typedef FilteredReducedKernel<ResultType, Iterator, MapFunctor, ReduceFunctor, Reducer> FilteredReduceType;
+    typedef SequenceHolder2<Sequence, FilteredReduceType, MapFunctor, ReduceFunctor> SequenceHolderType;
+    return startThreadEngine(new SequenceHolderType(sequence, mapFunctor, reduceFunctor, std::forward<ResultType>(initialValue), options));
+}
+
+//! [QtConcurrent-7]
+template <typename ResultType, typename Iterator, typename MapFunctor, typename ReduceFunctor>
+inline ThreadEngineStarter<ResultType> startFilteredReduced(Iterator begin, Iterator end,
+                                                           MapFunctor mapFunctor, ReduceFunctor reduceFunctor,
+                                                           ResultType &&initialValue,
+                                                           ReduceOptions options)
+{
+    typedef ReduceKernel<ReduceFunctor, ResultType, typename qValueType<Iterator>::value_type> Reducer;
+    typedef FilteredReducedKernel<ResultType, Iterator, MapFunctor, ReduceFunctor, Reducer> FilteredReduceType;
+    return startThreadEngine(new FilteredReduceType(begin, end, mapFunctor, reduceFunctor, std::forward<ResultType>(initialValue), options));
+}
+
 
 } // namespace QtConcurrent
 
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