CustomAttribute.cs

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using System.Reflection.Metadata.Ecma335;
 
namespace System.Reflection.Metadata;
 
public readonly struct CustomAttribute
{
    private readonly MetadataReader _reader;
 
    private readonly uint _treatmentAndRowId;
 
    private int RowId => (int)(_treatmentAndRowId & 0xFFFFFF);
 
    private CustomAttributeHandle Handle => CustomAttributeHandle.FromRowId(RowId);
 
    private MethodDefTreatment Treatment => (MethodDefTreatment)(_treatmentAndRowId >> 24);
 
    public EntityHandle Constructor => _reader.CustomAttributeTable.GetConstructor(Handle);
 
    public EntityHandle Parent => _reader.CustomAttributeTable.GetParent(Handle);
 
    public BlobHandle Value
    {
        get
        {
            if (Treatment == MethodDefTreatment.None)
            {
                return _reader.CustomAttributeTable.GetValue(Handle);
            }
            return GetProjectedValue();
        }
    }
 
    internal CustomAttribute(MetadataReader reader, uint treatmentAndRowId)
    {
        _reader = reader;
        _treatmentAndRowId = treatmentAndRowId;
    }
 
    public CustomAttributeValue<TType> DecodeValue<TType>(ICustomAttributeTypeProvider<TType> provider)
    {
        return new CustomAttributeDecoder<TType>(provider, _reader).DecodeValue(Constructor, Value);
    }
 
    private BlobHandle GetProjectedValue()
    {
        CustomAttributeValueTreatment customAttributeValueTreatment = _reader.CalculateCustomAttributeValueTreatment(Handle);
        if (customAttributeValueTreatment == CustomAttributeValueTreatment.None)
        {
            return _reader.CustomAttributeTable.GetValue(Handle);
        }
        return GetProjectedValue(customAttributeValueTreatment);
    }
 
    private BlobHandle GetProjectedValue(CustomAttributeValueTreatment treatment)
    {
        BlobHandle.VirtualIndex virtualIndex;
        bool flag;
        switch (treatment)
        {
        case CustomAttributeValueTreatment.AttributeUsageVersionAttribute:
        case CustomAttributeValueTreatment.AttributeUsageDeprecatedAttribute:
            virtualIndex = BlobHandle.VirtualIndex.AttributeUsage_AllowMultiple;
            flag = true;
            break;
        case CustomAttributeValueTreatment.AttributeUsageAllowMultiple:
            virtualIndex = BlobHandle.VirtualIndex.AttributeUsage_AllowMultiple;
            flag = false;
            break;
        case CustomAttributeValueTreatment.AttributeUsageAllowSingle:
            virtualIndex = BlobHandle.VirtualIndex.AttributeUsage_AllowSingle;
            flag = false;
            break;
        default:
            return default(BlobHandle);
        }
        BlobHandle value = _reader.CustomAttributeTable.GetValue(Handle);
        BlobReader blobReader = _reader.GetBlobReader(value);
        if (blobReader.Length != 8)
        {
            return value;
        }
        if (blobReader.ReadInt16() != 1)
        {
            return value;
        }
        AttributeTargets attributeTargets = ProjectAttributeTargetValue(blobReader.ReadUInt32());
        if (flag)
        {
            attributeTargets |= AttributeTargets.Constructor | AttributeTargets.Property;
        }
        return BlobHandle.FromVirtualIndex(virtualIndex, (ushort)attributeTargets);
    }
 
    private static AttributeTargets ProjectAttributeTargetValue(uint rawValue)
    {
        if (rawValue == uint.MaxValue)
        {
            return AttributeTargets.All;
        }
        AttributeTargets attributeTargets = (AttributeTargets)0;
        if ((rawValue & (true ? 1u : 0u)) != 0)
        {
            attributeTargets |= AttributeTargets.Delegate;
        }
        if ((rawValue & 2u) != 0)
        {
            attributeTargets |= AttributeTargets.Enum;
        }
        if ((rawValue & 4u) != 0)
        {
            attributeTargets |= AttributeTargets.Event;
        }
        if ((rawValue & 8u) != 0)
        {
            attributeTargets |= AttributeTargets.Field;
        }
        if ((rawValue & 0x10u) != 0)
        {
            attributeTargets |= AttributeTargets.Interface;
        }
        if ((rawValue & 0x40u) != 0)
        {
            attributeTargets |= AttributeTargets.Method;
        }
        if ((rawValue & 0x80u) != 0)
        {
            attributeTargets |= AttributeTargets.Parameter;
        }
        if ((rawValue & 0x100u) != 0)
        {
            attributeTargets |= AttributeTargets.Property;
        }
        if ((rawValue & 0x200u) != 0)
        {
            attributeTargets |= AttributeTargets.Class;
        }
        if ((rawValue & 0x400u) != 0)
        {
            attributeTargets |= AttributeTargets.Struct;
        }
        return attributeTargets;
    }
}