112 lines
2.7 KiB
Java
112 lines
2.7 KiB
Java
package com.bytezone.diskbrowser;
|
|
|
|
import java.util.Objects;
|
|
|
|
import com.bytezone.common.Utility;
|
|
|
|
class LZW2 extends LZW
|
|
{
|
|
private int nextEntry = 0x100;
|
|
private String prev = "";
|
|
private int codeWord;
|
|
|
|
public LZW2 (byte[] buffer, int crc)
|
|
{
|
|
bytes = Objects.requireNonNull (buffer);
|
|
|
|
this.crc = crc;
|
|
crcBase = 0xFFFF;
|
|
codeWord = 0;
|
|
|
|
volume = buffer[0] & 0xFF;
|
|
runLengthChar = (byte) (buffer[1] & 0xFF);
|
|
int ptr = 2;
|
|
|
|
while (ptr < buffer.length - 1) // what is in the last byte?
|
|
{
|
|
int rleLength = Utility.getWord (buffer, ptr);
|
|
boolean lzwPerformed = (rleLength & 0x8000) != 0;
|
|
ptr += 2;
|
|
|
|
if (lzwPerformed)
|
|
{
|
|
rleLength &= 0x0FFF; // remove the LZW flag
|
|
if (rleLength == 0)
|
|
rleLength = TRACK_LENGTH;
|
|
|
|
int chunkLength = Utility.getWord (buffer, ptr);
|
|
ptr += 2;
|
|
|
|
setBuffer (buffer, ptr); // prepare to read n-bit integers
|
|
byte[] lzwBuffer = undoLZW (rleLength);
|
|
|
|
assert (chunkLength - 4) == bytesRead ();
|
|
|
|
if (rleLength == TRACK_LENGTH) // no run length encoding
|
|
chunks.add (lzwBuffer);
|
|
else
|
|
chunks.add (undoRLE (lzwBuffer, 0, lzwBuffer.length));
|
|
|
|
ptr += bytesRead (); // since the setBuffer()
|
|
}
|
|
else
|
|
{
|
|
nextEntry = 0x100;
|
|
if (rleLength == 0)
|
|
rleLength = TRACK_LENGTH;
|
|
|
|
if (rleLength == TRACK_LENGTH) // no run length encoding
|
|
{
|
|
byte[] originalBuffer = new byte[TRACK_LENGTH];
|
|
System.arraycopy (buffer, ptr, originalBuffer, 0, originalBuffer.length);
|
|
chunks.add (originalBuffer);
|
|
}
|
|
else
|
|
chunks.add (undoRLE (buffer, ptr, rleLength));
|
|
|
|
ptr += rleLength;
|
|
}
|
|
}
|
|
}
|
|
|
|
protected byte[] undoLZW (int rleLength)
|
|
{
|
|
byte[] lzwBuffer = new byte[rleLength]; // must fill this array from buffer
|
|
int ptr = 0;
|
|
|
|
while (ptr < rleLength)
|
|
{
|
|
codeWord = readInt (width (nextEntry + 1));
|
|
|
|
if (codeWord == 0x100) // clear the table
|
|
{
|
|
nextEntry = 0x100;
|
|
codeWord = readInt (9);
|
|
prev = "";
|
|
}
|
|
|
|
String s = (nextEntry == codeWord) ? prev + prev.charAt (0) : st[codeWord];
|
|
|
|
if (nextEntry < st.length)
|
|
st[nextEntry++] = prev + s.charAt (0);
|
|
|
|
for (int i = 0; i < s.length (); i++)
|
|
lzwBuffer[ptr++] = (byte) s.charAt (i);
|
|
|
|
prev = s;
|
|
}
|
|
|
|
return lzwBuffer;
|
|
}
|
|
|
|
@Override
|
|
public String toString ()
|
|
{
|
|
StringBuilder text = new StringBuilder ();
|
|
|
|
text.append (String.format (" volume ............ %,d%n", volume));
|
|
text.append (String.format (" RLE char .......... $%02X", runLengthChar));
|
|
|
|
return text.toString ();
|
|
}
|
|
} |