GroupByQueryOperatorEnumerator.cs

Go to the documentation of this file.

using System.Collections.Generic;
using System.Diagnostics.CodeAnalysis;
using System.Threading;
 
namespace System.Linq.Parallel;
 
internal abstract class GroupByQueryOperatorEnumerator<TSource, TGroupKey, TElement, TOrderKey> : QueryOperatorEnumerator<IGrouping<TGroupKey, TElement>, TOrderKey>
{
    private sealed class Mutables
    {
        internal HashLookup<Wrapper<TGroupKey>, ListChunk<TElement>> _hashLookup;
 
        internal int _hashLookupIndex;
    }
 
    protected readonly QueryOperatorEnumerator<Pair<TSource, TGroupKey>, TOrderKey> _source;
 
    protected readonly IEqualityComparer<TGroupKey> _keyComparer;
 
    protected readonly CancellationToken _cancellationToken;
 
    private Mutables _mutables;
 
    protected GroupByQueryOperatorEnumerator(QueryOperatorEnumerator<Pair<TSource, TGroupKey>, TOrderKey> source, IEqualityComparer<TGroupKey> keyComparer, CancellationToken cancellationToken)
    {
        _source = source;
        _keyComparer = keyComparer;
        _cancellationToken = cancellationToken;
    }
 
    internal override bool MoveNext([MaybeNullWhen(false)][AllowNull] ref IGrouping<TGroupKey, TElement> currentElement, [AllowNull] ref TOrderKey currentKey)
    {
        Mutables mutables = _mutables;
        if (mutables == null)
        {
            mutables = (_mutables = new Mutables());
            mutables._hashLookup = BuildHashLookup();
            mutables._hashLookupIndex = -1;
        }
        if (++mutables._hashLookupIndex < mutables._hashLookup.Count)
        {
            currentElement = new GroupByGrouping<TGroupKey, TElement>(mutables._hashLookup[mutables._hashLookupIndex]);
            return true;
        }
        return false;
    }
 
    protected abstract HashLookup<Wrapper<TGroupKey>, ListChunk<TElement>> BuildHashLookup();
 
    protected override void Dispose(bool disposing)
    {
        _source.Dispose();
    }
}