org.archive.io.OriginSeekInputStream 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;
/**
* Alters the origin of some other SeekInputStream. This class allows you
* to completely ignore everything in the underlying stream before a specified
* position, the origin position.
*
* With the exception of {@link #position()} and {@link position(long)},
* all of the methods in this class simply delegate to the underlying input
* stream. The position methods adjust the position of the
* underlying stream relative to the origin specified at construction time.
*
* @author pjack
*/
public class OriginSeekInputStream extends SeekInputStream {
/**
* The underlying stream.
*/
final private SeekInputStream input;
/**
* The origin position. In other words, this.position(0)
* resolves to input.position(start).
*/
final private long origin;
/**
* Constructor.
*
* @param input the underlying stream
* @param origin the origin position
* @throws IOException if an IO error occurs
*/
public OriginSeekInputStream(SeekInputStream input, long origin)
throws IOException {
this.input = input;
this.origin = origin;
input.position(origin);
}
@Override
public int available() throws IOException {
return input.available();
}
@Override
public int read() throws IOException {
return input.read();
}
@Override
public int read(byte[] buf, int ofs, int len) throws IOException {
return input.read(buf, ofs, len);
}
@Override
public int read(byte[] buf) throws IOException {
return input.read(buf);
}
@Override
public long skip(long count) throws IOException {
return input.skip(count);
}
/**
* Returns the position of the underlying stream relative to the origin.
*
* @return the relative position
* @throws IOException if an IO error occurs
*/
public long position() throws IOException {
return input.position() - origin;
}
/**
* Positions the underlying stream relative to the origin.
* In other words, this.position(0) resolves to input.position(origin),
* where input is underlying stream and origin is the origin specified
* at construction time.
*
* @param p the new position for this stream
* @throws IOException if an IO error occurs
*/
public void position(long p) throws IOException {
input.position(p + origin);
}
}