GroupByElementSelectorQueryOperatorEnumerator.cs

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using System.Collections.Generic;
using System.Threading;
 
namespace System.Linq.Parallel;
 
internal sealed class GroupByElementSelectorQueryOperatorEnumerator<TSource, TGroupKey, TElement, TOrderKey> : GroupByQueryOperatorEnumerator<TSource, TGroupKey, TElement, TOrderKey>
{
    private readonly Func<TSource, TElement> _elementSelector;
 
    internal GroupByElementSelectorQueryOperatorEnumerator(QueryOperatorEnumerator<Pair<TSource, TGroupKey>, TOrderKey> source, IEqualityComparer<TGroupKey> keyComparer, Func<TSource, TElement> elementSelector, CancellationToken cancellationToken)
        : base(source, keyComparer, cancellationToken)
    {
        _elementSelector = elementSelector;
    }
 
    protected override HashLookup<Wrapper<TGroupKey>, ListChunk<TElement>> BuildHashLookup()
    {
        HashLookup<Wrapper<TGroupKey>, ListChunk<TElement>> hashLookup = new HashLookup<Wrapper<TGroupKey>, ListChunk<TElement>>(new WrapperEqualityComparer<TGroupKey>(_keyComparer));
        Pair<TSource, TGroupKey> currentElement = default(Pair<TSource, TGroupKey>);
        TOrderKey currentKey = default(TOrderKey);
        int num = 0;
        while (_source.MoveNext(ref currentElement, ref currentKey))
        {
            if ((num++ & 0x3F) == 0)
            {
                _cancellationToken.ThrowIfCancellationRequested();
            }
            Wrapper<TGroupKey> key = new Wrapper<TGroupKey>(currentElement.Second);
            ListChunk<TElement> value = null;
            if (!hashLookup.TryGetValue(key, ref value))
            {
                value = new ListChunk<TElement>(2);
                hashLookup.Add(key, value);
            }
            value.Add(_elementSelector(currentElement.First));
        }
        return hashLookup;
    }
}