private static int compareTo(byte[] buffer1, int offset1, int length1, byte[] buffer2,
    int offset2, int length2) {
    // Short circuit equal case
    if (buffer1 == buffer2 && offset1 == offset2 && length1 == length2) {
      return 0;
    }
    // Bring WritableComparator code local
    int end1 = offset1 + length1;
    int end2 = offset2 + length2;
    for (int i = offset1, j = offset2; i < end1 && j < end2; i++, j++) {
      int a = (buffer1[i] & 0xff);
      int b = (buffer2[j] & 0xff);
      if (a != b) {
        return a - b;
      }
    }
    return length1 - length2;
  }
Returns True if passed <code>bytes</code> has {@link #PB_MAGIC} for a prefix.
hbase-client/src/main/java/org/apache/hadoop/hbase/protobuf/ProtobufMagic.java