NullType.cs

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// 
//  Copyright 2010-2015 Deveel
// 
//    Licensed under the Apache License, Version 2.0 (the "License");
//    you may not use this file except in compliance with the License.
//    You may obtain a copy of the License at
// 
//        http://www.apache.org/licenses/LICENSE-2.0
// 
//    Unless required by applicable law or agreed to in writing, software
//    distributed under the License is distributed on an "AS IS" BASIS,
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//    See the License for the specific language governing permissions and
//    limitations under the License.
//

using System;
using System.IO;

using Deveel.Data.Serialization;
using Deveel.Data.Sql.Objects;

namespace Deveel.Data.Types {
    [Serializable]
    public sealed class NullType : SqlType {
        public NullType(SqlTypeCode typeCode) 
            : base("NULL", typeCode) {
        }

        private NullType(ObjectData data)
            : base(data) {
        }

        public override void SerializeObject(Stream stream, ISqlObject obj) {
            var writer = new BinaryWriter(stream);

            if (obj is SqlNull) {
                writer.Write((byte)1);
            } else if (obj == null || obj.IsNull) {
                writer.Write((byte) 2);
            } else {
                throw new FormatException();
            }
        }

        public override ISqlObject DeserializeObject(Stream stream) {
            var reader = new BinaryReader(stream);
            var type = reader.ReadByte();

            if (type == 1)
                return SqlNull.Value;
            if (type == 2) {
                // TODO: check the SQL Type Code of the type and construct the
                //       NULL value specific for the type.
                throw new NotImplementedException();
            }

            throw new FormatException();
        }

        public override object ConvertTo(ISqlObject obj, Type destType) {
            if (obj == null || obj.IsNull)
                return null;

            throw new InvalidCastException();
        }
    }
}