ParameterHandleCollection.cs

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using System.Collections;
using System.Collections.Generic;
 
namespace System.Reflection.Metadata;
 
public readonly struct ParameterHandleCollection : IReadOnlyCollection<ParameterHandle>, IEnumerable<ParameterHandle>, IEnumerable
{
    public struct Enumerator : IEnumerator<ParameterHandle>, IEnumerator, IDisposable
    {
        private readonly MetadataReader _reader;
 
        private readonly int _lastRowId;
 
        private int _currentRowId;
 
        public ParameterHandle Current
        {
            get
            {
                if (_reader.UseParamPtrTable)
                {
                    return GetCurrentParameterIndirect();
                }
                return ParameterHandle.FromRowId((int)((long)_currentRowId & 0xFFFFFFL));
            }
        }
 
        object IEnumerator.Current => Current;
 
        internal Enumerator(MetadataReader reader, int firstRowId, int lastRowId)
        {
            _reader = reader;
            _lastRowId = lastRowId;
            _currentRowId = firstRowId - 1;
        }
 
        private ParameterHandle GetCurrentParameterIndirect()
        {
            return _reader.ParamPtrTable.GetParamFor(_currentRowId & 0xFFFFFF);
        }
 
        public bool MoveNext()
        {
            if (_currentRowId >= _lastRowId)
            {
                _currentRowId = 16777216;
                return false;
            }
            _currentRowId++;
            return true;
        }
 
        void IEnumerator.Reset()
        {
            throw new NotSupportedException();
        }
 
        void IDisposable.Dispose()
        {
        }
    }
 
    private readonly MetadataReader _reader;
 
    private readonly int _firstRowId;
 
    private readonly int _lastRowId;
 
    public int Count => _lastRowId - _firstRowId + 1;
 
    internal ParameterHandleCollection(MetadataReader reader, MethodDefinitionHandle containingMethod)
    {
        _reader = reader;
        reader.GetParameterRange(containingMethod, out _firstRowId, out _lastRowId);
    }
 
    public Enumerator GetEnumerator()
    {
        return new Enumerator(_reader, _firstRowId, _lastRowId);
    }
 
    IEnumerator<ParameterHandle> IEnumerable<ParameterHandle>.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}