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#ifndef QTCONCURRENT_FILTERKERNEL_H
#define QTCONCURRENT_FILTERKERNEL_H

#include <QtConcurrent/qtconcurrent_global.h>

#if !defined(QT_NO_CONCURRENT) || defined (Q_CLANG_QDOC)

#include <QtConcurrent/qtconcurrentiteratekernel.h>
#include <QtConcurrent/qtconcurrentmapkernel.h>
#include <QtConcurrent/qtconcurrentreducekernel.h>

QT_BEGIN_NAMESPACE



namespace QtConcurrent {

template <typename T>
struct qValueType
{
    typedef typename T::value_type value_type;
};

template <typename T>
struct qValueType<const T*>
{
    typedef T value_type;
};

template <typename T>
struct qValueType<T*>
{
    typedef T value_type;
};

// Implementation of filter
template <typename Sequence, typename KeepFunctor, typename ReduceFunctor>
class FilterKernel : public IterateKernel<typename Sequence::const_iterator, void>
{
    typedef ReduceKernel<ReduceFunctor, Sequence, typename Sequence::value_type> Reducer;
    typedef IterateKernel<typename Sequence::const_iterator, void> IterateKernelType;
    typedef void T;

    Sequence reducedResult;
    Sequence &sequence;
    KeepFunctor keep;
    ReduceFunctor reduce;
    Reducer reducer;

public:
    FilterKernel(QThreadPool *pool, Sequence &_sequence, KeepFunctor _keep, ReduceFunctor _reduce)
        : IterateKernelType(pool, const_cast<const Sequence &>(_sequence).begin(),
                            const_cast<const Sequence &>(_sequence).end()), reducedResult(),
          sequence(_sequence),
          keep(_keep),
          reduce(_reduce),
          reducer(pool, OrderedReduce)
    { }

    bool runIteration(typename Sequence::const_iterator it, int index, T *) override
    {
        IntermediateResults<typename Sequence::value_type> results;
        results.begin = index;
        results.end = index + 1;

        if (std::invoke(keep, *it))
            results.vector.append(*it);

        reducer.runReduce(reduce, reducedResult, results);
        return false;
    }

    bool runIterations(typename Sequence::const_iterator sequenceBeginIterator, int begin, int end, T *) override
    {
        IntermediateResults<typename Sequence::value_type> results;
        results.begin = begin;
        results.end = end;
        results.vector.reserve(end - begin);


        typename Sequence::const_iterator it = sequenceBeginIterator;
        std::advance(it, begin);
        for (int i = begin; i < end; ++i) {
            if (std::invoke(keep, *it))
                results.vector.append(*it);
            std::advance(it, 1);
        }

        reducer.runReduce(reduce, reducedResult, results);
        return false;
    }

    void finish() override
    {
        reducer.finish(reduce, reducedResult);
        sequence = reducedResult;
    }

    inline bool shouldThrottleThread() override
    {
        return IterateKernelType::shouldThrottleThread() || reducer.shouldThrottle();
    }

    inline bool shouldStartThread() override
    {
        return IterateKernelType::shouldStartThread() && reducer.shouldStartThread();
    }

    typedef void ReturnType;
    typedef void ResultType;
};

// Implementation of filter-reduce
template <typename ReducedResultType,
          typename Iterator,
          typename KeepFunctor,
          typename ReduceFunctor,
          typename Reducer = ReduceKernel<ReduceFunctor,
                                          ReducedResultType,
                                          typename qValueType<Iterator>::value_type> >
class FilteredReducedKernel : public IterateKernel<Iterator, ReducedResultType>
{
    ReducedResultType reducedResult;
    KeepFunctor keep;
    ReduceFunctor reduce;
    Reducer reducer;
    typedef IterateKernel<Iterator, ReducedResultType> IterateKernelType;

public:
    FilteredReducedKernel(QThreadPool *pool,
                          Iterator begin,
                          Iterator end,
                          KeepFunctor _keep,
                          ReduceFunctor _reduce,
                          ReduceOptions reduceOption)
        : IterateKernelType(pool, begin, end), reducedResult(), keep(_keep), reduce(_reduce),
          reducer(pool, reduceOption)
    { }

    FilteredReducedKernel(QThreadPool *pool, Iterator begin, Iterator end, KeepFunctor _keep,
                          ReduceFunctor _reduce, ReducedResultType &&initialValue,
                          ReduceOptions reduceOption)
        : IterateKernelType(pool, begin, end),
          reducedResult(std::forward<ReducedResultType>(initialValue)),
          keep(_keep),
          reduce(_reduce),
          reducer(pool, reduceOption)
    {
    }

    bool runIteration(Iterator it, int index, ReducedResultType *) override
    {
        IntermediateResults<typename qValueType<Iterator>::value_type> results;
        results.begin = index;
        results.end = index + 1;

        if (std::invoke(keep, *it))
            results.vector.append(*it);

        reducer.runReduce(reduce, reducedResult, results);
        return false;
    }

    bool runIterations(Iterator sequenceBeginIterator, int begin, int end, ReducedResultType *) override
    {
        IntermediateResults<typename qValueType<Iterator>::value_type> results;
        results.begin = begin;
        results.end = end;
        results.vector.reserve(end - begin);

        Iterator it = sequenceBeginIterator;
        std::advance(it, begin);
        for (int i = begin; i < end; ++i) {
            if (std::invoke(keep, *it))
                results.vector.append(*it);
            std::advance(it, 1);
        }

        reducer.runReduce(reduce, reducedResult, results);
        return false;
    }

    void finish() override
    {
        reducer.finish(reduce, reducedResult);
    }

    inline bool shouldThrottleThread() override
    {
        return IterateKernelType::shouldThrottleThread() || reducer.shouldThrottle();
    }

    inline bool shouldStartThread() override
    {
        return IterateKernelType::shouldStartThread() && reducer.shouldStartThread();
    }

    typedef ReducedResultType ReturnType;
    typedef ReducedResultType ResultType;
    ReducedResultType *result() override
    {
        return &reducedResult;
    }
};

// Implementation of filter that reports individual results via QFutureInterface
template <typename Iterator, typename KeepFunctor>
class FilteredEachKernel : public IterateKernel<Iterator, typename qValueType<Iterator>::value_type>
{
    typedef typename qValueType<Iterator>::value_type T;
    typedef IterateKernel<Iterator, T> IterateKernelType;

    KeepFunctor keep;

public:
    typedef T ReturnType;
    typedef T ResultType;

    FilteredEachKernel(QThreadPool *pool, Iterator begin, Iterator end, KeepFunctor _keep)
        : IterateKernelType(pool, begin, end), keep(_keep)
    { }

    void start() override
    {
        if (this->futureInterface)
            this->futureInterface->setFilterMode(true);
        IterateKernelType::start();
    }

    bool runIteration(Iterator it, int index, T *) override
    {
        if (std::invoke(keep, *it))
            this->reportResult(&(*it), index);
        else
            this->reportResult(nullptr, index);
        return false;
    }

    bool runIterations(Iterator sequenceBeginIterator, int begin, int end, T *) override
    {
        const int count = end - begin;
        IntermediateResults<typename qValueType<Iterator>::value_type> results;
        results.begin = begin;
        results.end = end;
        results.vector.reserve(count);

        Iterator it = sequenceBeginIterator;
        std::advance(it, begin);
        for (int i = begin; i < end; ++i) {
            if (std::invoke(keep, *it))
                results.vector.append(*it);
            std::advance(it, 1);
        }

        this->reportResults(results.vector, begin, count);
        return false;
    }
};

//! [QtConcurrent-2]
template <typename Iterator, typename KeepFunctor>
inline
ThreadEngineStarter<typename qValueType<Iterator>::value_type>
startFiltered(QThreadPool *pool, Iterator begin, Iterator end, KeepFunctor functor)
{
    return startThreadEngine(new FilteredEachKernel<Iterator, KeepFunctor>
                             (pool, begin, end, functor));
}

//! [QtConcurrent-3]
template <typename Sequence, typename KeepFunctor>
inline ThreadEngineStarter<typename Sequence::value_type>
startFiltered(QThreadPool *pool, const Sequence &sequence, KeepFunctor functor)
{
    typedef SequenceHolder1<Sequence,
                            FilteredEachKernel<typename Sequence::const_iterator, KeepFunctor>,
                            KeepFunctor>
        SequenceHolderType;
        return startThreadEngine(new SequenceHolderType(pool, sequence, functor));
}

//! [QtConcurrent-4]
template <typename ResultType, typename Sequence, typename MapFunctor, typename ReduceFunctor>
inline ThreadEngineStarter<ResultType> startFilteredReduced(QThreadPool *pool,
                                                            const Sequence &sequence,
                                                            MapFunctor mapFunctor,
                                                            ReduceFunctor reduceFunctor,
                                                            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(pool, sequence, mapFunctor,
                                                    reduceFunctor, options));
}


//! [QtConcurrent-5]
template <typename ResultType, typename Iterator, typename MapFunctor, typename ReduceFunctor>
inline ThreadEngineStarter<ResultType> startFilteredReduced(QThreadPool *pool,
                                                            Iterator begin,
                                                            Iterator end,
                                                            MapFunctor mapFunctor,
                                                            ReduceFunctor reduceFunctor,
                                                            ReduceOptions options)
{
    typedef ReduceKernel<ReduceFunctor, ResultType, typename qValueType<Iterator>::value_type>
            Reducer;
    typedef FilteredReducedKernel<ResultType, Iterator, MapFunctor, ReduceFunctor, Reducer>
            FilteredReduceType;
    return startThreadEngine(new FilteredReduceType(pool, 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(QThreadPool *pool,
                                                            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(pool, sequence, mapFunctor, reduceFunctor,
                             std::forward<ResultType>(initialValue), options));
}

//! [QtConcurrent-7]
template <typename ResultType, typename Iterator, typename MapFunctor, typename ReduceFunctor>
inline ThreadEngineStarter<ResultType> startFilteredReduced(QThreadPool *pool,
                                                            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(pool, begin, end, mapFunctor, reduceFunctor,
                             std::forward<ResultType>(initialValue), options));
}


} // namespace QtConcurrent


QT_END_NAMESPACE

#endif // QT_NO_CONCURRENT

#endif
