code: def _detect_xerial_stream(payload):
      
  
      if len(payload) > 16:
          header = struct.unpack('!' + _XERIAL_V1_FORMAT, bytes(payload)[:16])
          return header == _XERIAL_V1_HEADER
      return False
docs: Detects if the data given might have been encoded with the blocking mode
          of the xerial snappy library.
  
          This mode writes a magic header of the format:
              +--------+--------------+------------+---------+--------+
              | Marker | Magic String | Null / Pad | Version | Compat |
              +--------+--------------+------------+---------+--------+
              |  byte  |   c-string   |    byte    |  int32  | int32  |
              +--------+--------------+------------+---------+--------+
              |  -126  |   'SNAPPY'   |     \0     |         |        |
              +--------+--------------+------------+---------+--------+
  
          The pad appears to be to ensure that SNAPPY is a valid cstring
          The version is the version of this format as written by xerial,
          in the wild this is currently 1 as such we only support v1.
  
          Compat is there to claim the miniumum supported version that
          can read a xerial block stream, presently in the wild this is
          1.