/**
* 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.hadoop.contrib.index.lucene;
import java.io.IOException;
import org.apache.lucene.store.Directory;
/**
* This class copies some methods from Lucene's SegmentInfos since that class
* is not public.
*/
public final class LuceneUtil {
static final class IndexFileNames {
/** Name of the index segment file */
static final String SEGMENTS = "segments";
/** Name of the generation reference file name */
static final String SEGMENTS_GEN = "segments.gen";
}
/**
* Check if the file is a segments_N file
* @param name
* @return true if the file is a segments_N file
*/
public static boolean isSegmentsFile(String name) {
return name.startsWith(IndexFileNames.SEGMENTS)
&& !name.equals(IndexFileNames.SEGMENTS_GEN);
}
/**
* Check if the file is the segments.gen file
* @param name
* @return true if the file is the segments.gen file
*/
public static boolean isSegmentsGenFile(String name) {
return name.equals(IndexFileNames.SEGMENTS_GEN);
}
/**
* Get the generation (N) of the current segments_N file in the directory.
*
* @param directory -- directory to search for the latest segments_N file
*/
public static long getCurrentSegmentGeneration(Directory directory)
throws IOException {
String[] files = directory.list();
if (files == null)
throw new IOException("cannot read directory " + directory
+ ": list() returned null");
return getCurrentSegmentGeneration(files);
}
/**
* Get the generation (N) of the current segments_N file from a list of
* files.
*
* @param files -- array of file names to check
*/
public static long getCurrentSegmentGeneration(String[] files) {
if (files == null) {
return -1;
}
long max = -1;
for (int i = 0; i < files.length; i++) {
String file = files[i];
if (file.startsWith(IndexFileNames.SEGMENTS)
&& !file.equals(IndexFileNames.SEGMENTS_GEN)) {
long gen = generationFromSegmentsFileName(file);
if (gen > max) {
max = gen;
}
}
}
return max;
}
/**
* Parse the generation off the segments file name and return it.
*/
public static long generationFromSegmentsFileName(String fileName) {
if (fileName.equals(IndexFileNames.SEGMENTS)) {
return 0;
} else if (fileName.startsWith(IndexFileNames.SEGMENTS)) {
return Long.parseLong(
fileName.substring(1 + IndexFileNames.SEGMENTS.length()),
Character.MAX_RADIX);
} else {
throw new IllegalArgumentException("fileName \"" + fileName
+ "\" is not a segments file");
}
}
}