113 lines
2.3 KiB
Java
113 lines
2.3 KiB
Java
package com.bytezone.diskbrowser;
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import java.util.ArrayList;
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import java.util.List;
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class LZW
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{
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static protected final String[] st = new String[0x1000];
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static protected final int TRACK_LENGTH = 0x1000;
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protected final List<byte[]> chunks = new ArrayList<byte[]> ();
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protected int volume;
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protected byte runLengthChar;
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protected int crc;
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protected int crcBase;
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private int buffer; // one character buffer
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private int bitsLeft; // unused bits left in buffer
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private int ptr;
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private int startPtr;
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protected byte[] bytes;
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static
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{
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for (int i = 0; i < 256; i++)
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st[i] = "" + (char) i;
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}
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public void setBuffer (byte[] buffer, int ptr)
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{
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bytes = buffer;
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startPtr = this.ptr = ptr;
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bitsLeft = 0;
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}
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public int bytesRead ()
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{
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return ptr - startPtr;
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}
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private void fillBuffer ()
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{
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buffer = bytes[ptr++] & 0xFF;
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bitsLeft = 8;
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}
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private boolean readBoolean ()
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{
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if (bitsLeft == 0)
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fillBuffer ();
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bitsLeft--;
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boolean bit = ((buffer << bitsLeft) & 0x80) == 0x80;
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return bit;
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}
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protected int readInt (int width)
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{
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if (width < 8 || width > 12)
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throw new RuntimeException ("Illegal value of r = " + width);
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int x = 0;
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for (int i = 0, weight = 1; i < width; i++, weight <<= 1)
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if (readBoolean ())
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x |= weight;
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return x;
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}
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protected byte[] undoRLE (byte[] inBuffer, int inPtr, int length)
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{
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byte[] outBuffer = new byte[TRACK_LENGTH];
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int outPtr = 0;
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int max = inPtr + length;
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while (inPtr < max)
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{
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byte b = inBuffer[inPtr++];
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if (b == runLengthChar)
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{
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b = inBuffer[inPtr++];
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int rpt = inBuffer[inPtr++] & 0xFF;
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while (rpt-- >= 0)
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outBuffer[outPtr++] = b;
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}
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else
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outBuffer[outPtr++] = b;
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}
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assert outPtr == TRACK_LENGTH;
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return outBuffer;
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}
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public byte[] getData ()
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{
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byte[] buffer = new byte[chunks.size () * TRACK_LENGTH];
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int trackNumber = 0;
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for (byte[] track : chunks)
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System.arraycopy (track, 0, buffer, trackNumber++ * TRACK_LENGTH, TRACK_LENGTH);
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if (crc != NuFX.getCRC (buffer, crcBase))
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System.out.println ("\n*** LZW CRC mismatch ***");
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return buffer;
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}
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protected int width (int maximumValue)
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{
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return 32 - Integer.numberOfLeadingZeros (maximumValue);
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}
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} |