LocalScopeHandleCollection.cs

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using System.Collections;
using System.Collections.Generic;
 
namespace System.Reflection.Metadata;
 
public readonly struct LocalScopeHandleCollection : IReadOnlyCollection<LocalScopeHandle>, IEnumerable<LocalScopeHandle>, IEnumerable
{
    public struct Enumerator : IEnumerator<LocalScopeHandle>, IEnumerator, IDisposable
    {
        private readonly MetadataReader _reader;
 
        private readonly int _lastRowId;
 
        private int _currentRowId;
 
        public LocalScopeHandle Current => LocalScopeHandle.FromRowId((int)((long)_currentRowId & 0xFFFFFFL));
 
        object IEnumerator.Current => Current;
 
        internal Enumerator(MetadataReader reader, int firstRowId, int lastRowId)
        {
            _reader = reader;
            _lastRowId = lastRowId;
            _currentRowId = firstRowId - 1;
        }
 
        public bool MoveNext()
        {
            if (_currentRowId >= _lastRowId)
            {
                _currentRowId = 16777216;
                return false;
            }
            _currentRowId++;
            return true;
        }
 
        void IEnumerator.Reset()
        {
            throw new NotSupportedException();
        }
 
        void IDisposable.Dispose()
        {
        }
    }
 
    public struct ChildrenEnumerator : IEnumerator<LocalScopeHandle>, IEnumerator, IDisposable
    {
        private readonly MetadataReader _reader;
 
        private readonly int _parentEndOffset;
 
        private readonly int _parentRowId;
 
        private readonly MethodDefinitionHandle _parentMethodRowId;
 
        private int _currentRowId;
 
        public LocalScopeHandle Current => LocalScopeHandle.FromRowId((int)((long)_currentRowId & 0xFFFFFFL));
 
        object IEnumerator.Current => Current;
 
        internal ChildrenEnumerator(MetadataReader reader, int parentRowId)
        {
            _reader = reader;
            _parentEndOffset = reader.LocalScopeTable.GetEndOffset(parentRowId);
            _parentMethodRowId = reader.LocalScopeTable.GetMethod(parentRowId);
            _currentRowId = 0;
            _parentRowId = parentRowId;
        }
 
        public bool MoveNext()
        {
            int currentRowId = _currentRowId;
            int num;
            int num2;
            switch (currentRowId)
            {
            case 16777216:
                return false;
            case 0:
                num = -1;
                num2 = _parentRowId + 1;
                break;
            default:
                num = _reader.LocalScopeTable.GetEndOffset(currentRowId);
                num2 = currentRowId + 1;
                break;
            }
            int numberOfRows = _reader.LocalScopeTable.NumberOfRows;
            int endOffset;
            while (true)
            {
                if (num2 > numberOfRows || _parentMethodRowId != _reader.LocalScopeTable.GetMethod(num2))
                {
                    _currentRowId = 16777216;
                    return false;
                }
                endOffset = _reader.LocalScopeTable.GetEndOffset(num2);
                if (endOffset > num)
                {
                    break;
                }
                num2++;
            }
            if (endOffset > _parentEndOffset)
            {
                _currentRowId = 16777216;
                return false;
            }
            _currentRowId = num2;
            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 LocalScopeHandleCollection(MetadataReader reader, int methodDefinitionRowId)
    {
        _reader = reader;
        if (methodDefinitionRowId == 0)
        {
            _firstRowId = 1;
            _lastRowId = reader.LocalScopeTable.NumberOfRows;
        }
        else
        {
            reader.LocalScopeTable.GetLocalScopeRange(methodDefinitionRowId, out _firstRowId, out _lastRowId);
        }
    }
 
    public Enumerator GetEnumerator()
    {
        return new Enumerator(_reader, _firstRowId, _lastRowId);
    }
 
    IEnumerator<LocalScopeHandle> IEnumerable<LocalScopeHandle>.GetEnumerator()
    {
        return GetEnumerator();
    }
 
    IEnumerator IEnumerable.GetEnumerator()
    {
        return GetEnumerator();
    }
}