1 package org.apache.lucene.store;
4 * Licensed to the Apache Software Foundation (ASF) under one or more
5 * contributor license agreements. See the NOTICE file distributed with
6 * this work for additional information regarding copyright ownership.
7 * The ASF licenses this file to You under the Apache License, Version 2.0
8 * (the "License"); you may not use this file except in compliance with
9 * the License. You may obtain a copy of the License at
11 * http://www.apache.org/licenses/LICENSE-2.0
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS,
15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
20 import java.io.IOException;
21 import java.util.zip.CRC32;
22 import java.util.zip.Checksum;
24 /** Writes bytes through to a primary IndexOutput, computing
25 * checksum. Note that you cannot use seek().
29 public class ChecksumIndexOutput extends IndexOutput {
33 public ChecksumIndexOutput(IndexOutput main) {
39 public void writeByte(byte b) throws IOException {
45 public void writeBytes(byte[] b, int offset, int length) throws IOException {
46 digest.update(b, offset, length);
47 main.writeBytes(b, offset, length);
50 public long getChecksum() {
51 return digest.getValue();
55 public void flush() throws IOException {
60 public void close() throws IOException {
65 public long getFilePointer() {
66 return main.getFilePointer();
70 public void seek(long pos) {
71 throw new RuntimeException("not allowed");
75 * Starts but does not complete the commit of this file (=
76 * writing of the final checksum at the end). After this
77 * is called must call {@link #finishCommit} and the
78 * {@link #close} to complete the commit.
80 public void prepareCommit() throws IOException {
81 final long checksum = getChecksum();
82 // Intentionally write a mismatched checksum. This is
83 // because we want to 1) test, as best we can, that we
84 // are able to write a long to the file, but 2) not
85 // actually "commit" the file yet. This (prepare
86 // commit) is phase 1 of a two-phase commit.
87 final long pos = main.getFilePointer();
88 main.writeLong(checksum-1);
93 /** See {@link #prepareCommit} */
94 public void finishCommit() throws IOException {
95 main.writeLong(getChecksum());
99 public long length() throws IOException {
100 return main.length();