LocalVariableTableReader.cs

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using System.Reflection.Internal;
 
namespace System.Reflection.Metadata.Ecma335;
 
internal readonly struct LocalVariableTableReader
{
    internal readonly int NumberOfRows;
 
    private readonly bool _isStringHeapRefSizeSmall;
 
    private readonly int _attributesOffset;
 
    private readonly int _indexOffset;
 
    private readonly int _nameOffset;
 
    internal readonly int RowSize;
 
    internal readonly MemoryBlock Block;
 
    internal LocalVariableTableReader(int numberOfRows, int stringHeapRefSize, MemoryBlock containingBlock, int containingBlockOffset)
    {
        NumberOfRows = numberOfRows;
        _isStringHeapRefSizeSmall = stringHeapRefSize == 2;
        _attributesOffset = 0;
        _indexOffset = _attributesOffset + 2;
        _nameOffset = _indexOffset + 2;
        RowSize = _nameOffset + stringHeapRefSize;
        Block = containingBlock.GetMemoryBlockAt(containingBlockOffset, RowSize * numberOfRows);
    }
 
    internal LocalVariableAttributes GetAttributes(LocalVariableHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return (LocalVariableAttributes)Block.PeekUInt16(num + _attributesOffset);
    }
 
    internal ushort GetIndex(LocalVariableHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return Block.PeekUInt16(num + _indexOffset);
    }
 
    internal StringHandle GetName(LocalVariableHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return StringHandle.FromOffset(Block.PeekHeapReference(num + _nameOffset, _isStringHeapRefSizeSmall));
    }
}