| /* |
| * 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. |
| */ |
| package org.apache.lucene.store; |
| |
| import java.io.IOException; |
| |
| |
| /** |
| * Extension of IndexInput, computing checksum as it goes. |
| * Callers can retrieve the checksum via {@link #getChecksum()}. |
| */ |
| public abstract class ChecksumIndexInput extends IndexInput { |
| |
| /** resourceDescription should be a non-null, opaque string |
| * describing this resource; it's returned from |
| * {@link #toString}. */ |
| protected ChecksumIndexInput(String resourceDescription) { |
| super(resourceDescription); |
| } |
| |
| /** Returns the current checksum value */ |
| public abstract long getChecksum() throws IOException; |
| |
| /** |
| * {@inheritDoc} |
| * |
| * {@link 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. |
| */ |
| @Override |
| public void seek(long pos) throws IOException { |
| final long curFP = getFilePointer(); |
| final long skip = pos - curFP; |
| if (skip < 0) { |
| throw new IllegalStateException(getClass() + " cannot seek backwards (pos=" + pos + " getFilePointer()=" + curFP + ")"); |
| } |
| skipBytes(skip); |
| } |
| } |