/**
* compress the source array. use rllchar as character to indicate repetition. if rllchar is 0x0,
* the least frequent character from source will be used.
*
* @return a newly created array with the rll compressed data.
*/
public static byte[] compress(byte rllchar, byte[] source) {
if (rllchar == (byte) 0) {
int[] freq = HuffmanTree.constructTable(source);
int min = 100000;
for (int i = 0; i < freq.length; i++) {
if (freq[i] == 0) {
rllchar = (byte) i;
break;
}
if (freq[i] < min) {
min = freq[i];
rllchar = (byte) i;
}
}
}
ByteArrayOutputStream baos = new ByteArrayOutputStream(source.length);
baos.write(rllchar);
int i;
for (i = 0; i < source.length - 3; i++) {
if ((source[i] == source[i + 1]) && (source[i + 1] == source[i + 2])) {
int rep = 3;
while (((i + rep) < source.length) && source[i + rep] == source[i]) {
if (rep == 254) break;
rep++;
}
baos.write(rllchar);
baos.write(rep);
baos.write(source[i]);
i += rep - 1;
} else if (source[i] == rllchar) {
baos.write(rllchar);
baos.write(1);
} else {
baos.write(source[i]);
}
}
while (i < source.length) {
baos.write(source[i++]);
}
return baos.toByteArray();
}
