OrderedPartition.cs

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using System.Collections;
using System.Collections.Generic;
 
namespace System.Linq;
 
internal sealed class OrderedPartition<TElement> : IPartition<TElement>, IIListProvider<TElement>, IEnumerable<TElement>, IEnumerable
{
    private readonly OrderedEnumerable<TElement> _source;
 
    private readonly int _minIndexInclusive;
 
    private readonly int _maxIndexInclusive;
 
    public OrderedPartition(OrderedEnumerable<TElement> source, int minIdxInclusive, int maxIdxInclusive)
    {
        _source = source;
        _minIndexInclusive = minIdxInclusive;
        _maxIndexInclusive = maxIdxInclusive;
    }
 
    public IEnumerator<TElement> GetEnumerator()
    {
        return _source.GetEnumerator(_minIndexInclusive, _maxIndexInclusive);
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    public IPartition<TElement> Skip(int count)
    {
        int num = _minIndexInclusive + count;
        if ((uint)num <= (uint)_maxIndexInclusive)
        {
            return new OrderedPartition<TElement>(_source, num, _maxIndexInclusive);
        }
        return EmptyPartition<TElement>.Instance;
    }
 
    public IPartition<TElement> Take(int count)
    {
        int num = _minIndexInclusive + count - 1;
        if ((uint)num >= (uint)_maxIndexInclusive)
        {
            return this;
        }
        return new OrderedPartition<TElement>(_source, _minIndexInclusive, num);
    }
 
    public TElement TryGetElementAt(int index, out bool found)
    {
        if ((uint)index <= (uint)(_maxIndexInclusive - _minIndexInclusive))
        {
            return _source.TryGetElementAt(index + _minIndexInclusive, out found);
        }
        found = false;
        return default(TElement);
    }
 
    public TElement TryGetFirst(out bool found)
    {
        return _source.TryGetElementAt(_minIndexInclusive, out found);
    }
 
    public TElement TryGetLast(out bool found)
    {
        return _source.TryGetLast(_minIndexInclusive, _maxIndexInclusive, out found);
    }
 
    public TElement[] ToArray()
    {
        return _source.ToArray(_minIndexInclusive, _maxIndexInclusive);
    }
 
    public List<TElement> ToList()
    {
        return _source.ToList(_minIndexInclusive, _maxIndexInclusive);
    }
 
    public int GetCount(bool onlyIfCheap)
    {
        return _source.GetCount(_minIndexInclusive, _maxIndexInclusive, onlyIfCheap);
    }
}