RangeEnumerable.cs

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using System.Collections.Generic;
 
namespace System.Linq.Parallel;
 
internal sealed class RangeEnumerable : ParallelQuery<int>, IParallelPartitionable<int>
{
    private sealed class RangeEnumerator : QueryOperatorEnumerator<int, int>
    {
        private readonly int _from;
 
        private readonly int _count;
 
        private readonly int _initialIndex;
 
        private Shared<int> _currentCount;
 
        internal RangeEnumerator(int from, int count, int initialIndex)
        {
            _from = from;
            _count = count;
            _initialIndex = initialIndex;
        }
 
        internal override bool MoveNext(ref int currentElement, ref int currentKey)
        {
            if (_currentCount == null)
            {
                _currentCount = new Shared<int>(-1);
            }
            int num = _currentCount.Value + 1;
            if (num < _count)
            {
                _currentCount.Value = num;
                currentElement = num + _from;
                currentKey = num + _initialIndex;
                return true;
            }
            return false;
        }
 
        internal override void Reset()
        {
            _currentCount = null;
        }
    }
 
    private readonly int _from;
 
    private readonly int _count;
 
    internal RangeEnumerable(int from, int count)
        : base(QuerySettings.Empty)
    {
        _from = from;
        _count = count;
    }
 
    public QueryOperatorEnumerator<int, int>[] GetPartitions(int partitionCount)
    {
        int num = _count / partitionCount;
        int num2 = _count % partitionCount;
        int num3 = 0;
        QueryOperatorEnumerator<int, int>[] array = new QueryOperatorEnumerator<int, int>[partitionCount];
        for (int i = 0; i < partitionCount; i++)
        {
            int num4 = ((i < num2) ? (num + 1) : num);
            array[i] = new RangeEnumerator(_from + num3, num4, num3);
            num3 += num4;
        }
        return array;
    }
 
    public override IEnumerator<int> GetEnumerator()
    {
        return new RangeEnumerator(_from, _count, 0).AsClassicEnumerator();
    }
}