Apple-2-Tools/AppleCommander
1
0
Fork 0
mirror of https://github.com/AppleCommander/AppleCommander.git synced 2024-12-22 08:30:35 +00:00
Code Issues Projects Releases Wiki Activity

Added the Apple IIGS "UnPackBytes" routine.

Browse Source
This commit is contained in:
Robert Greene 2003-01-09 04:45:55 +00:00
parent 0a0fa50dda
commit f6e9d4556e
1 changed files with 62 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

62
src/com/webcodepro/applecommander/storage/AppleUtil.java
View File

@ -19,6 +19,9 @@
*/
package com.webcodepro.applecommander.storage;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.Date;
import java.util.GregorianCalendar;
@ -308,4 +311,63 @@ public class AppleUtil {
}
return buf.toString();
}
/**
* Mimic the Apple IIGS UnPackBytes method call. The compression is
* very similar the RLE, but has the following coding conventions:<br>
* 00xx xxxx = 1 to 64 bytes follow (all different)<br>
* 01xx xxxx = 3, 5, 6, or 7 repeats of next byte<br>
* 10xx xxxx = 1 to 64 repeats of next 4 bytes<br>
* 11xx xxxx = 1 to 64 repeats of next byte taken as 4 bytes<br>
* The 6 data bits are stored as length-1; hence 000000 is a length of
* 1 and 111111 is a length of 64.
*/
public static byte[] unpackBytes(byte[] compressedData) {
ByteArrayOutputStream decompressedStream =
new ByteArrayOutputStream(compressedData.length * 2);
int offset = 0;
byte data;
byte[] dataArray = new byte[4];
while (offset < compressedData.length) {
byte header = compressedData[offset++];
int length = (header & 0x3f) + 1; // 0x3f = 00111111
switch (header & 0xc0) { // 0xc0 = 11000000
case 0x00: // 00xx xxxx (copy)
for (int i=0; i<length; i++) {
decompressedStream.write(compressedData[offset++]);
}
break;
case 0x40: // 01xx xxxx (repeat byte)
data = compressedData[offset++];
for (int i=0; i<length; i++) {
decompressedStream.write(data);
}
break;
case 0x80: // 10xx xxxx (repeat next 4 bytes)
for (int i=0; i<4; i++) {
dataArray[i] = compressedData[offset++];
}
for (int i=0; i<length; i++) {
try {
decompressedStream.write(dataArray);
} catch (IOException ignored) {
}
}
break;
case 0xc0: // 11xx xxxx (repeat byte 4 times length)
data = compressedData[offset++];
for (int i=0; i<4; i++) {
dataArray[i] = data;
}
for (int i=0; i<length; i++) {
try {
decompressedStream.write(dataArray);
} catch (IOException ignored) {
}
}
break;
}
}
return decompressedStream.toByteArray();
}
}