GenericParamTableReader.cs

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using System.Reflection.Internal;
 
namespace System.Reflection.Metadata.Ecma335;
 
internal readonly struct GenericParamTableReader
{
    internal readonly int NumberOfRows;
 
    private readonly bool _IsTypeOrMethodDefRefSizeSmall;
 
    private readonly bool _IsStringHeapRefSizeSmall;
 
    private readonly int _NumberOffset;
 
    private readonly int _FlagsOffset;
 
    private readonly int _OwnerOffset;
 
    private readonly int _NameOffset;
 
    internal readonly int RowSize;
 
    internal readonly MemoryBlock Block;
 
    internal GenericParamTableReader(int numberOfRows, bool declaredSorted, int typeOrMethodDefRefSize, int stringHeapRefSize, MemoryBlock containingBlock, int containingBlockOffset)
    {
        NumberOfRows = numberOfRows;
        _IsTypeOrMethodDefRefSizeSmall = typeOrMethodDefRefSize == 2;
        _IsStringHeapRefSizeSmall = stringHeapRefSize == 2;
        _NumberOffset = 0;
        _FlagsOffset = _NumberOffset + 2;
        _OwnerOffset = _FlagsOffset + 2;
        _NameOffset = _OwnerOffset + typeOrMethodDefRefSize;
        RowSize = _NameOffset + stringHeapRefSize;
        Block = containingBlock.GetMemoryBlockAt(containingBlockOffset, RowSize * numberOfRows);
        if (!declaredSorted && !CheckSorted())
        {
            Throw.TableNotSorted(TableIndex.GenericParam);
        }
    }
 
    internal ushort GetNumber(GenericParameterHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return Block.PeekUInt16(num + _NumberOffset);
    }
 
    internal GenericParameterAttributes GetFlags(GenericParameterHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return (GenericParameterAttributes)Block.PeekUInt16(num + _FlagsOffset);
    }
 
    internal StringHandle GetName(GenericParameterHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return StringHandle.FromOffset(Block.PeekHeapReference(num + _NameOffset, _IsStringHeapRefSizeSmall));
    }
 
    internal EntityHandle GetOwner(GenericParameterHandle handle)
    {
        int num = (handle.RowId - 1) * RowSize;
        return TypeOrMethodDefTag.ConvertToHandle(Block.PeekTaggedReference(num + _OwnerOffset, _IsTypeOrMethodDefRefSizeSmall));
    }
 
    internal GenericParameterHandleCollection FindGenericParametersForType(TypeDefinitionHandle typeDef)
    {
        ushort genericParamCount = 0;
        uint searchCodedTag = TypeOrMethodDefTag.ConvertTypeDefRowIdToTag(typeDef);
        int firstRowId = BinarySearchTag(searchCodedTag, ref genericParamCount);
        return new GenericParameterHandleCollection(firstRowId, genericParamCount);
    }
 
    internal GenericParameterHandleCollection FindGenericParametersForMethod(MethodDefinitionHandle methodDef)
    {
        ushort genericParamCount = 0;
        uint searchCodedTag = TypeOrMethodDefTag.ConvertMethodDefToTag(methodDef);
        int firstRowId = BinarySearchTag(searchCodedTag, ref genericParamCount);
        return new GenericParameterHandleCollection(firstRowId, genericParamCount);
    }
 
    private int BinarySearchTag(uint searchCodedTag, ref ushort genericParamCount)
    {
        Block.BinarySearchReferenceRange(NumberOfRows, RowSize, _OwnerOffset, searchCodedTag, _IsTypeOrMethodDefRefSizeSmall, out var startRowNumber, out var endRowNumber);
        if (startRowNumber == -1)
        {
            genericParamCount = 0;
            return 0;
        }
        genericParamCount = (ushort)(endRowNumber - startRowNumber + 1);
        return startRowNumber + 1;
    }
 
    private bool CheckSorted()
    {
        return Block.IsOrderedByReferenceAscending(RowSize, _OwnerOffset, _IsTypeOrMethodDefRefSizeSmall);
    }
}