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