GenericParameterHandleCollection.cs

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using System.Collections;
using System.Collections.Generic;
 
namespace System.Reflection.Metadata;
 
public readonly struct GenericParameterHandleCollection : IReadOnlyList<GenericParameterHandle>, IEnumerable<GenericParameterHandle>, IEnumerable, IReadOnlyCollection<GenericParameterHandle>
{
    public struct Enumerator : IEnumerator<GenericParameterHandle>, IEnumerator, IDisposable
    {
        private readonly int _lastRowId;
 
        private int _currentRowId;
 
        public GenericParameterHandle Current => GenericParameterHandle.FromRowId((int)((long)_currentRowId & 0xFFFFFFL));
 
        object IEnumerator.Current => Current;
 
        internal Enumerator(int firstRowId, int lastRowId)
        {
            _currentRowId = firstRowId - 1;
            _lastRowId = lastRowId;
        }
 
        public bool MoveNext()
        {
            if (_currentRowId >= _lastRowId)
            {
                _currentRowId = 16777216;
                return false;
            }
            _currentRowId++;
            return true;
        }
 
        void IEnumerator.Reset()
        {
            throw new NotSupportedException();
        }
 
        void IDisposable.Dispose()
        {
        }
    }
 
    private readonly int _firstRowId;
 
    private readonly ushort _count;
 
    public int Count => _count;
 
    public GenericParameterHandle this[int index]
    {
        get
        {
            if (index < 0 || index >= _count)
            {
                Throw.IndexOutOfRange();
            }
            return GenericParameterHandle.FromRowId(_firstRowId + index);
        }
    }
 
    internal GenericParameterHandleCollection(int firstRowId, ushort count)
    {
        _firstRowId = firstRowId;
        _count = count;
    }
 
    public Enumerator GetEnumerator()
    {
        return new Enumerator(_firstRowId, _firstRowId + _count - 1);
    }
 
    IEnumerator<GenericParameterHandle> IEnumerable<GenericParameterHandle>.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}