DataReaderContainer.cs

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using System.Data.Common;
using System.Diagnostics.CodeAnalysis;
 
namespace System.Data.ProviderBase;
 
internal abstract class DataReaderContainer
{
    private sealed class ProviderSpecificDataReader : DataReaderContainer
    {
        private readonly DbDataReader _providerSpecificDataReader;
 
        internal override bool ReturnProviderSpecificTypes => true;
 
        protected override int VisibleFieldCount
        {
            get
            {
                int visibleFieldCount = _providerSpecificDataReader.VisibleFieldCount;
                if (0 > visibleFieldCount)
                {
                    return 0;
                }
                return visibleFieldCount;
            }
        }
 
        internal ProviderSpecificDataReader(IDataReader dataReader, DbDataReader dbDataReader)
            : base(dataReader)
        {
            _providerSpecificDataReader = dbDataReader;
            _fieldCount = VisibleFieldCount;
        }
 
        [return: DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields | DynamicallyAccessedMemberTypes.PublicProperties)]
        internal override Type GetFieldType(int ordinal)
        {
            return _providerSpecificDataReader.GetProviderSpecificFieldType(ordinal);
        }
 
        internal override int GetValues(object[] values)
        {
            return _providerSpecificDataReader.GetProviderSpecificValues(values);
        }
    }
 
    private sealed class CommonLanguageSubsetDataReader : DataReaderContainer
    {
        internal override bool ReturnProviderSpecificTypes => false;
 
        protected override int VisibleFieldCount
        {
            get
            {
                int fieldCount = _dataReader.FieldCount;
                if (0 > fieldCount)
                {
                    return 0;
                }
                return fieldCount;
            }
        }
 
        internal CommonLanguageSubsetDataReader(IDataReader dataReader)
            : base(dataReader)
        {
            _fieldCount = VisibleFieldCount;
        }
 
        [return: DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields | DynamicallyAccessedMemberTypes.PublicProperties)]
        internal override Type GetFieldType(int ordinal)
        {
            return _dataReader.GetFieldType(ordinal);
        }
 
        internal override int GetValues(object[] values)
        {
            return _dataReader.GetValues(values);
        }
    }
 
    protected readonly IDataReader _dataReader;
 
    protected int _fieldCount;
 
    internal int FieldCount => _fieldCount;
 
    internal abstract bool ReturnProviderSpecificTypes { get; }
 
    protected abstract int VisibleFieldCount { get; }
 
    internal static DataReaderContainer Create(IDataReader dataReader, bool returnProviderSpecificTypes)
    {
        if (returnProviderSpecificTypes && dataReader is DbDataReader dbDataReader)
        {
            return new ProviderSpecificDataReader(dataReader, dbDataReader);
        }
        return new CommonLanguageSubsetDataReader(dataReader);
    }
 
    protected DataReaderContainer(IDataReader dataReader)
    {
        _dataReader = dataReader;
    }
 
    [return: DynamicallyAccessedMembers(DynamicallyAccessedMemberTypes.PublicFields | DynamicallyAccessedMemberTypes.PublicProperties)]
    internal abstract Type GetFieldType(int ordinal);
 
    internal abstract int GetValues(object[] values);
 
    internal string GetName(int ordinal)
    {
        string name = _dataReader.GetName(ordinal);
        if (name == null)
        {
            return "";
        }
        return name;
    }
 
    internal DataTable GetSchemaTable()
    {
        return _dataReader.GetSchemaTable();
    }
 
    internal bool NextResult()
    {
        _fieldCount = 0;
        if (_dataReader.NextResult())
        {
            _fieldCount = VisibleFieldCount;
            return true;
        }
        return false;
    }
 
    internal bool Read()
    {
        return _dataReader.Read();
    }
}