mirror of
https://github.com/dmolony/DiskBrowser.git
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109 lines
2.7 KiB
Java
109 lines
2.7 KiB
Java
package com.bytezone.diskbrowser.wizardry;
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import com.bytezone.diskbrowser.applefile.AbstractFile;
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// Based on a pascal routine by Tom Ewers
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public class Huffman extends AbstractFile
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{
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private final byte[] tree;
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private final byte[] left;
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private final byte[] right;
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private int bitNo;
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private int msgPtr;
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private int currentByte;
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private byte[] message;
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private String treeContents;
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public Huffman (String name, byte[] buffer)
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{
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super (name, buffer);
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tree = new byte[256];
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left = new byte[256];
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right = new byte[256];
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System.arraycopy (buffer, 0, tree, 0, 256);
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System.arraycopy (buffer, 256, left, 0, 256);
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System.arraycopy (buffer, 512, right, 0, 256);
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}
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public String getMessage (byte[] message)
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{
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this.message = message;
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bitNo = 0;
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msgPtr = 0;
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currentByte = 0;
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int len = getChar ();
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StringBuilder text = new StringBuilder ();
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for (int i = 0; i < len; i++)
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text.append ((char) getChar ());
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return text.toString ();
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}
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private byte getChar ()
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{
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int treePtr = 0; // start at the root
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while (true)
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{
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if (bitNo-- == 0)
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{
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bitNo += 8;
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currentByte = message[msgPtr++] & 0xFF;
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}
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int currentBit = currentByte % 2; // get the next bit to process
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currentByte /= 2;
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if (currentBit == 0) // take right path
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{
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if ((tree[treePtr] & 0x02) != 0) // if has right leaf...
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return right[treePtr]; // return that character
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treePtr = right[treePtr] & 0xFF; // else go to right node
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}
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else // take left path
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{
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if ((tree[treePtr] & 0x01) != 0) // if has left leaf...
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return left[treePtr]; // return that character
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treePtr = left[treePtr] & 0xFF; // else go to left node
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}
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}
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}
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@Override
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public String getText ()
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{
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if (treeContents == null)
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{
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StringBuilder text = new StringBuilder ();
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walk (0, "", text);
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treeContents = text.toString ();
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}
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return treeContents;
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}
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private void walk (int treePtr, String path, StringBuilder text)
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{
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if ((tree[treePtr] & 0x01) == 0)
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walk (left[treePtr] & 0xFF, path + "1", text);
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else
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print (path + "1", left[treePtr], text);
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if ((tree[treePtr] & 0x02) == 0)
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walk (right[treePtr] & 0xFF, path + "0", text);
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else
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print (path + "0", right[treePtr], text);
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}
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private void print (String path, byte value, StringBuilder text)
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{
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int val = value & 0xFF;
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char c = val < 32 || val >= 127 ? ' ' : (char) val;
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text.append (String.format ("%3d %1.1s %s%n", val, c, path));
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}
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} |