protected final String hexDump(int offset, int len) {
    return Hex.dump(bytes, offset, len, offset, hexCols, 4);
  }
Constructs a hex data dump of the given portion of {@link #bytes}.

@param offset offset to start dumping at
@param len length to dump
@return {@code non-null;} the dump
android/android_framework/dex-maker/src/main/java/com/android/dx/command/dump/BaseDumper.java