src.org.tukaani.xz.SeekableInputStream Maven / Gradle / Ivy
/*
* SeekableInputStream
*
* Author: Lasse Collin
*
* This file has been put into the public domain.
* You can do whatever you want with this file.
*/
package org.tukaani.xz;
import java.io.InputStream;
import java.io.IOException;
/**
* Input stream with random access support.
*/
public abstract class SeekableInputStream extends InputStream {
/**
* Seeks n bytes forward in this stream.
*
* This will not seek past the end of the file. If the current position
* is already at or past the end of the file, this doesn't seek at all
* and returns 0. Otherwise, if skipping n bytes
* would cause the position to exceed the stream size, this will do
* equivalent of seek(length()) and the return value will
* be adjusted accordingly.
*
* If n is negative, the position isn't changed and
* the return value is 0. It doesn't seek backward
* because it would conflict with the specification of
* {@link java.io.InputStream#skip(long) InputStream.skip}.
*
* @return 0 if n is negative,
* less than n if skipping n
* bytes would seek past the end of the file,
* n otherwise
*
* @throws IOException might be thrown by {@link #seek(long)}
*/
public long skip(long n) throws IOException {
if (n <= 0)
return 0;
long size = length();
long pos = position();
if (pos >= size)
return 0;
if (size - pos < n)
n = size - pos;
seek(pos + n);
return n;
}
/**
* Gets the size of the stream.
*/
public abstract long length() throws IOException;
/**
* Gets the current position in the stream.
*/
public abstract long position() throws IOException;
/**
* Seeks to the specified absolute position in the stream.
*
* Seeking past the end of the file should be supported by the subclasses
* unless there is a good reason to do otherwise. If one has seeked
* past the end of the stream, read will return
* -1 to indicate end of stream.
*
* @param pos new read position in the stream
*
* @throws IOException if pos is negative or if
* a stream-specific I/O error occurs
*/
public abstract void seek(long pos) throws IOException;
}