org.archive.io.SeekReader Maven / Gradle / Ivy
/*
* This file is part of the Heritrix web crawler (crawler.archive.org).
*
* Licensed to the Internet Archive (IA) by one or more individual
* contributors.
*
* The IA 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.archive.io;
import java.io.IOException;
import java.io.Reader;
import it.unimi.dsi.fastutil.io.RepositionableStream;
/**
* Base class for repositionable readers.
*
* @author pjack
*/
public abstract class SeekReader extends Reader
implements RepositionableStream {
/**
* The marked file position. A value less than zero
* indicates that no mark has been set.
*/
private long mark = -1;
/**
* Marks the current position of the stream. The limit parameter is
* ignored; the mark will remain valid until reset is called or the
* stream is closed.
*
* @param limit ignored
*/
@Override
public void mark(int limit) {
try {
this.mark = position();
} catch (IOException e) {
mark = -1;
}
}
/**
* Resets this stream to its marked position.
*
* @throws IOException if there is no mark, or if an IO error occurs
*/
@Override
public void reset() throws IOException {
if (mark < 0) {
throw new IOException("No mark.");
}
position(mark);
}
/**
* Returns true, since SeekInputStreams support mark/reset by default.
*
* @return true
*/
@Override
public boolean markSupported() {
return true;
}
}