dmolony-DiskBrowser/src/com/bytezone/diskbrowser/LZW.java
2015-06-01 19:35:51 +10:00

113 lines
2.3 KiB
Java

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