code: private long fourByteToLong(byte[] bytes, int offset) {
          return (byteToLong(bytes[offset + 0])
                  + (byteToLong(bytes[offset + 1]) << 8)
                  + (byteToLong(bytes[offset + 2]) << 16)
                  + (byteToLong(bytes[offset + 3]) << 24));
      }
docs: Convert 4 bytes from the buffer at offset into a long value.