package org.apache.lucene.index;
/**
* Copyright 2004 The Apache Software Foundation
*
* Licensed 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.
*/
import java.util.Vector;
import java.io.IOException;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.InputStream;
import org.apache.lucene.store.OutputStream;
final class SegmentInfos extends Vector {
/** The file format version, a negative number. */
/* Works since counter, the old 1st entry, is always >= 0 */
public static final int FORMAT = -1;
public int counter = 0; // used to name new segments
private long version = 0; //counts how often the index has been changed by adding or deleting docs
public final SegmentInfo info(int i) {
return (SegmentInfo) elementAt(i);
}
public final void read(Directory directory) throws IOException {
InputStream input = directory.openFile("segments");
try {
int format = input.readInt();
if(format < 0){ // file contains explicit format info
// check that it is a format we can understand
if (format < FORMAT)
throw new IOException("Unknown format version: " + format);
version = input.readLong(); // read version
counter = input.readInt(); // read counter
}
else{ // file is in old format without explicit format info
counter = format;
}
for (int i = input.readInt(); i > 0; i--) { // read segmentInfos
SegmentInfo si =
new SegmentInfo(input.readString(), input.readInt(), directory);
addElement(si);
}
if(format >= 0){ // in old format the version number may be at the end of the file
if (input.getFilePointer() >= input.length())
version = 0; // old file format without version number
else
version = input.readLong(); // read version
}
}
finally {
input.close();
}
}
public final void write(Directory directory) throws IOException {
OutputStream output = directory.createFile("segments.new");
try {
output.writeInt(FORMAT); // write FORMAT
output.writeLong(++version); // every write changes the index
output.writeInt(counter); // write counter
output.writeInt(size()); // write infos
for (int i = 0; i < size(); i++) {
SegmentInfo si = info(i);
output.writeString(si.name);
output.writeInt(si.docCount);
}
}
finally {
output.close();
}
// install new segment info
directory.renameFile("segments.new", "segments");
}
/**
* version number when this SegmentInfos was generated.
*/
public long getVersion() {
return version;
}
/**
* Current version number from segments file.
*/
public static long readCurrentVersion(Directory directory)
throws IOException {
InputStream input = directory.openFile("segments");
int format = 0;
long version = 0;
try {
format = input.readInt();
if(format < 0){
if (format < FORMAT)
throw new IOException("Unknown format version: " + format);
version = input.readLong(); // read version
}
}
finally {
input.close();
}
if(format < 0)
return version;
// We cannot be sure about the format of the file.
// Therefore we have to read the whole file and cannot simply seek to the version entry.
SegmentInfos sis = new SegmentInfos();
sis.read(directory);
return sis.getVersion();
}
}