src.org.tukaani.xz.DeltaOptions Maven / Gradle / Ivy
/*
* DeltaOptions
*
* 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;
/**
* Delta filter options. The Delta filter can be used only as a non-last
* filter in the chain, for example Delta + LZMA2.
*
* Currently only simple byte-wise delta is supported. The only option
* is the delta distance, which you should set to match your data.
* It's not possible to provide a generic default value for it.
*
* For example, with distance = 2 and eight-byte input
* A1 B1 A2 B3 A3 B5 A4 B7, the output will be A1 B1 01 02 01 02 01 02.
*
* The Delta filter can be good with uncompressed bitmap images. It can
* also help with PCM audio, although special-purpose compressors like
* FLAC will give much smaller result at much better compression speed.
*/
public class DeltaOptions extends FilterOptions {
/**
* Smallest supported delta calculation distance.
*/
public static final int DISTANCE_MIN = 1;
/**
* Largest supported delta calculation distance.
*/
public static final int DISTANCE_MAX = 256;
private int distance = DISTANCE_MIN;
/**
* Creates new Delta options and sets the delta distance to 1 byte.
*/
public DeltaOptions() {}
/**
* Creates new Delta options and sets the distance to the given value.
*/
public DeltaOptions(int distance) throws UnsupportedOptionsException {
setDistance(distance);
}
/**
* Sets the delta distance in bytes. The new distance must be in
* the range [DISTANCE_MIN, DISTANCE_MAX].
*/
public void setDistance(int distance) throws UnsupportedOptionsException {
if (distance < DISTANCE_MIN || distance > DISTANCE_MAX)
throw new UnsupportedOptionsException(
"Delta distance must be in the range [" + DISTANCE_MIN
+ ", " + DISTANCE_MAX + "]: " + distance);
this.distance = distance;
}
/**
* Gets the delta distance.
*/
public int getDistance() {
return distance;
}
public int getEncoderMemoryUsage() {
return DeltaOutputStream.getMemoryUsage();
}
public FinishableOutputStream getOutputStream(FinishableOutputStream out) {
return new DeltaOutputStream(out, this);
}
public int getDecoderMemoryUsage() {
return 1;
}
public InputStream getInputStream(InputStream in) {
return new DeltaInputStream(in, distance);
}
FilterEncoder getFilterEncoder() {
return new DeltaEncoder(this);
}
public Object clone() {
try {
return super.clone();
} catch (CloneNotSupportedException e) {
assert false;
throw new RuntimeException();
}
}
}