| using System; |
| |
| namespace Lucene.Net.Store |
| { |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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. |
| */ |
| |
| /// <summary> |
| /// Extension of <see cref="IndexInput"/>, computing checksum as it goes. |
| /// Callers can retrieve the checksum via <see cref="Checksum"/>. |
| /// </summary> |
| public abstract class ChecksumIndexInput : IndexInput |
| { |
| /// <summary> |
| /// <paramref name="resourceDescription"/> should be a non-null, opaque string |
| /// describing this resource; it's returned from |
| /// <see cref="object.ToString()"/>. |
| /// </summary> |
| protected ChecksumIndexInput(string resourceDescription) |
| : base(resourceDescription) |
| { |
| } |
| |
| /// <summary> |
| /// Returns the current checksum value </summary> |
| public abstract long Checksum { get; } |
| |
| /// <summary> |
| /// Sets current position in this file, where the next read will occur. |
| /// <para/> |
| /// <see cref="ChecksumIndexInput"/> can only seek forward and seeks are expensive |
| /// since they imply to read bytes in-between the current position and the |
| /// target position in order to update the checksum. |
| /// </summary> |
| public override void Seek(long pos) |
| { |
| long skip = pos - GetFilePointer(); |
| if (skip < 0) |
| { |
| throw new InvalidOperationException(this.GetType() + " cannot seek backwards"); |
| } |
| SkipBytes(skip); |
| } |
| } |
| } |