_tmp_unpack_run.java

import java.nio.file.*;
import com.runescape.cache.bzip.BZip2Decompressor;

public class UnpackRun {
    public static void main(String[] args) throws Exception {
        byte[] input = Files.readAllBytes(Path.of(args[0]));
        int compressedLen = ((input[1] & 0xFF) << 24) | ((input[2] & 0xFF) << 16) | ((input[3] & 0xFF) << 8) | (input[4] & 0xFF);
        int outputLen = ((input[5] & 0xFF) << 24) | ((input[6] & 0xFF) << 16) | ((input[7] & 0xFF) << 8) | (input[8] & 0xFF);
        byte[] compressed = new byte[compressedLen];
        System.arraycopy(input, 9, compressed, 0, compressedLen);
        byte[] output = new byte[outputLen];
        BZip2Decompressor.decompress(output, outputLen, compressed, compressedLen, 0);
        Files.write(Path.of(args[1]), output);
        System.out.println("ok " + output.length);
    }
}