/*
* 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.index;
import java.util.regex.Pattern;
import org.apache.lucene.codecs.Codec;
/**
* This class contains useful constants representing filenames and extensions
* used by lucene, as well as convenience methods for querying whether a file
* name matches an extension ({@link #matchesExtension(String, String)
* matchesExtension}), as well as generating file names from a segment name,
* generation and extension (
* {@link #fileNameFromGeneration(String, String, long) fileNameFromGeneration},
* {@link #segmentFileName(String, String, String) segmentFileName}).
*
* <p><b>NOTE</b>: extensions used by codecs are not
* listed here. You must interact with the {@link Codec}
* directly.
*
* @lucene.internal
*/
public final class IndexFileNames {
/** No instance */
private IndexFileNames() {}
/** Name of the index segment file */
public static final String SEGMENTS = "segments";
/** Name of pending index segment file */
public static final String PENDING_SEGMENTS = "pending_segments";
/** Name of the generation reference file name */
public static final String OLD_SEGMENTS_GEN = "segments.gen";
/**
* Computes the full file name from base, extension and generation. If the
* generation is -1, the file name is null. If it's 0, the file name is
* <base>.<ext>. If it's > 0, the file name is
* <base>_<gen>.<ext>.<br>
* <b>NOTE:</b> .<ext> is added to the name only if <code>ext</code> is
* not an empty string.
*
* @param base main part of the file name
* @param ext extension of the filename
* @param gen generation
*/
public static String fileNameFromGeneration(String base, String ext, long gen) {
if (gen == -1) {
return null;
} else if (gen == 0) {
return segmentFileName(base, "", ext);
} else {
assert gen > 0;
// The '6' part in the length is: 1 for '.', 1 for '_' and 4 as estimate
// to the gen length as string (hopefully an upper limit so SB won't
// expand in the middle.
StringBuilder res = new StringBuilder(base.length() + 6 + ext.length())
.append(base).append('_').append(Long.toString(gen, Character.MAX_RADIX));
if (ext.length() > 0) {
res.append('.').append(ext);
}
return res.toString();
}
}
/**
* Returns a file name that includes the given segment name, your own custom
* name and extension. The format of the filename is:
* <segmentName>(_<name>)(.<ext>).
* <p>
* <b>NOTE:</b> .<ext> is added to the result file name only if
* <code>ext</code> is not empty.
* <p>
* <b>NOTE:</b> _<segmentSuffix> is added to the result file name only if
* it's not the empty string
* <p>
* <b>NOTE:</b> all custom files should be named using this method, or
* otherwise some structures may fail to handle them properly (such as if they
* are added to compound files).
*/
public static String segmentFileName(String segmentName, String segmentSuffix, String ext) {
if (ext.length() > 0 || segmentSuffix.length() > 0) {
assert !ext.startsWith(".");
StringBuilder sb = new StringBuilder(segmentName.length() + 2 + segmentSuffix.length() + ext.length());
sb.append(segmentName);
if (segmentSuffix.length() > 0) {
sb.append('_').append(segmentSuffix);
}
if (ext.length() > 0) {
sb.append('.').append(ext);
}
return sb.toString();
} else {
return segmentName;
}
}
/**
* Returns true if the given filename ends with the given extension. One
* should provide a <i>pure</i> extension, without '.'.
*/
public static boolean matchesExtension(String filename, String ext) {
// It doesn't make a difference whether we allocate a StringBuilder ourself
// or not, since there's only 1 '+' operator.
return filename.endsWith("." + ext);
}
/** locates the boundary of the segment name, or -1 */
private static int indexOfSegmentName(String filename) {
// If it is a .del file, there's an '_' after the first character
int idx = filename.indexOf('_', 1);
if (idx == -1) {
// If it's not, strip everything that's before the '.'
idx = filename.indexOf('.');
}
return idx;
}
/**
* Strips the segment name out of the given file name. If you used
* {@link #segmentFileName} or {@link #fileNameFromGeneration} to create your
* files, then this method simply removes whatever comes before the first '.',
* or the second '_' (excluding both).
*
* @return the filename with the segment name removed, or the given filename
* if it does not contain a '.' and '_'.
*/
public static String stripSegmentName(String filename) {
int idx = indexOfSegmentName(filename);
if (idx != -1) {
filename = filename.substring(idx);
}
return filename;
}
/** Returns the generation from this file name, or 0 if there is no
* generation. */
public static long parseGeneration(String filename) {
assert filename.startsWith("_");
String parts[] = stripExtension(filename).substring(1).split("_");
// 4 cases:
// segment.ext
// segment_gen.ext
// segment_codec_suffix.ext
// segment_gen_codec_suffix.ext
if (parts.length == 2 || parts.length == 4) {
return Long.parseLong(parts[1], Character.MAX_RADIX);
} else {
return 0;
}
}
/**
* Parses the segment name out of the given file name.
*
* @return the segment name only, or filename
* if it does not contain a '.' and '_'.
*/
public static String parseSegmentName(String filename) {
int idx = indexOfSegmentName(filename);
if (idx != -1) {
filename = filename.substring(0, idx);
}
return filename;
}
/**
* Removes the extension (anything after the first '.'),
* otherwise returns the original filename.
*/
public static String stripExtension(String filename) {
int idx = filename.indexOf('.');
if (idx != -1) {
filename = filename.substring(0, idx);
}
return filename;
}
/**
* Return the extension (anything after the first '.'),
* or null if there is no '.' in the file name.
*/
public static String getExtension(String filename) {
final int idx = filename.indexOf('.');
if (idx == -1) {
return null;
} else {
return filename.substring(idx + 1, filename.length());
}
}
/**
* All files created by codecs much match this pattern (checked in
* SegmentInfo).
*/
public static final Pattern CODEC_FILE_PATTERN = Pattern.compile("_[a-z0-9]+(_.*)?\\..*");
}