HashRepartitionEnumerator.cs

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using System.Threading;
 
namespace System.Linq.Parallel;
 
internal sealed class HashRepartitionEnumerator<TInputOutput, THashKey, TIgnoreKey> : QueryOperatorEnumerator<Pair<TInputOutput, THashKey>, int>
{
    private sealed class Mutables
    {
        internal int _currentBufferIndex;
 
        internal ListChunk<Pair<TInputOutput, THashKey>> _currentBuffer;
 
        internal int _currentIndex;
 
        internal Mutables()
        {
            _currentBufferIndex = -1;
        }
    }
 
    private readonly int _partitionCount;
 
    private readonly int _partitionIndex;
 
    private readonly Func<TInputOutput, THashKey> _keySelector;
 
    private readonly HashRepartitionStream<TInputOutput, THashKey, int> _repartitionStream;
 
    private readonly ListChunk<Pair<TInputOutput, THashKey>>[][] _valueExchangeMatrix;
 
    private readonly QueryOperatorEnumerator<TInputOutput, TIgnoreKey> _source;
 
    private CountdownEvent _barrier;
 
    private readonly CancellationToken _cancellationToken;
 
    private Mutables _mutables;
 
    internal HashRepartitionEnumerator(QueryOperatorEnumerator<TInputOutput, TIgnoreKey> source, int partitionCount, int partitionIndex, Func<TInputOutput, THashKey> keySelector, HashRepartitionStream<TInputOutput, THashKey, int> repartitionStream, CountdownEvent barrier, ListChunk<Pair<TInputOutput, THashKey>>[][] valueExchangeMatrix, CancellationToken cancellationToken)
    {
        _source = source;
        _partitionCount = partitionCount;
        _partitionIndex = partitionIndex;
        _keySelector = keySelector;
        _repartitionStream = repartitionStream;
        _barrier = barrier;
        _valueExchangeMatrix = valueExchangeMatrix;
        _cancellationToken = cancellationToken;
    }
 
    internal override bool MoveNext(ref Pair<TInputOutput, THashKey> currentElement, ref int currentKey)
    {
        if (_partitionCount == 1)
        {
            TIgnoreKey currentKey2 = default(TIgnoreKey);
            TInputOutput currentElement2 = default(TInputOutput);
            if (_source.MoveNext(ref currentElement2, ref currentKey2))
            {
                currentElement = new Pair<TInputOutput, THashKey>(currentElement2, (_keySelector == null) ? default(THashKey) : _keySelector(currentElement2));
                return true;
            }
            return false;
        }
        Mutables mutables = _mutables;
        if (mutables == null)
        {
            mutables = (_mutables = new Mutables());
        }
        if (mutables._currentBufferIndex == -1)
        {
            EnumerateAndRedistributeElements();
        }
        while (mutables._currentBufferIndex < _partitionCount)
        {
            if (mutables._currentBuffer != null)
            {
                if (++mutables._currentIndex < mutables._currentBuffer.Count)
                {
                    currentElement = mutables._currentBuffer._chunk[mutables._currentIndex];
                    return true;
                }
                mutables._currentIndex = -1;
                mutables._currentBuffer = mutables._currentBuffer.Next;
                continue;
            }
            if (mutables._currentBufferIndex == _partitionIndex)
            {
                _barrier.Wait(_cancellationToken);
                mutables._currentBufferIndex = -1;
            }
            mutables._currentBufferIndex++;
            mutables._currentIndex = -1;
            if (mutables._currentBufferIndex == _partitionIndex)
            {
                mutables._currentBufferIndex++;
            }
            if (mutables._currentBufferIndex < _partitionCount)
            {
                mutables._currentBuffer = _valueExchangeMatrix[mutables._currentBufferIndex][_partitionIndex];
            }
        }
        return false;
    }
 
    private void EnumerateAndRedistributeElements()
    {
        Mutables mutables = _mutables;
        ListChunk<Pair<TInputOutput, THashKey>>[] array = new ListChunk<Pair<TInputOutput, THashKey>>[_partitionCount];
        TInputOutput currentElement = default(TInputOutput);
        TIgnoreKey currentKey = default(TIgnoreKey);
        int num = 0;
        while (_source.MoveNext(ref currentElement, ref currentKey))
        {
            if ((num++ & 0x3F) == 0)
            {
                _cancellationToken.ThrowIfCancellationRequested();
            }
            THashKey val = default(THashKey);
            int num2;
            if (_keySelector != null)
            {
                val = _keySelector(currentElement);
                num2 = _repartitionStream.GetHashCode(val) % _partitionCount;
            }
            else
            {
                num2 = _repartitionStream.GetHashCode(currentElement) % _partitionCount;
            }
            ListChunk<Pair<TInputOutput, THashKey>> listChunk = array[num2];
            if (listChunk == null)
            {
                listChunk = (array[num2] = new ListChunk<Pair<TInputOutput, THashKey>>(128));
            }
            listChunk.Add(new Pair<TInputOutput, THashKey>(currentElement, val));
        }
        for (int i = 0; i < _partitionCount; i++)
        {
            _valueExchangeMatrix[_partitionIndex][i] = array[i];
        }
        _barrier.Signal();
        mutables._currentBufferIndex = _partitionIndex;
        mutables._currentBuffer = array[_partitionIndex];
        mutables._currentIndex = -1;
    }
 
    protected override void Dispose(bool disposed)
    {
        if (_barrier != null)
        {
            if (_mutables == null || _mutables._currentBufferIndex == -1)
            {
                _barrier.Signal();
                _barrier = null;
            }
            _source.Dispose();
        }
    }
}