pykerl.py 文件源码

def squeeze(self, trits, offset=0, length=None):
    # type: (MutableSequence[int], int, Optional[int]) -> None
    """
    Squeeze trits from the sponge into a buffer.

    :param trits:
      Buffer that will hold the squeezed trits.

      IMPORTANT:  If ``trits`` is too small, it will be extended!

    :param offset:
      Starting offset in ``trits``.

    :param length:
      Number of trits to squeeze from the sponge.

      If not specified, defaults to :py:data:`TRIT_HASH_LENGTH` (i.e.,
      by default, we will try to squeeze exactly 1 hash).
    """
    # Pad input if necessary, so that it can be divided evenly into
    # hashes.
    pad = ((len(trits) % TRIT_HASH_LENGTH) or TRIT_HASH_LENGTH)
    trits += [0] * (TRIT_HASH_LENGTH - pad)

    if length is None:
      # By default, we will try to squeeze one hash.
      # Note that this is different than ``absorb``.
      length = len(trits) or TRIT_HASH_LENGTH

    if length < 1:
      raise with_context(
        exc = ValueError('Invalid length passed to ``squeeze``.'),

        context = {
          'trits': trits,
          'offset': offset,
          'length': length,
        },
      )

    while offset < length:
      unsigned_hash = self.k.digest()

      if PY2:
        unsigned_hash = map(ord, unsigned_hash) # type: ignore

      signed_hash = [conv.convert_sign(b) for b in unsigned_hash]

      trits_from_hash = conv.convertToTrits(signed_hash)
      trits_from_hash[TRIT_HASH_LENGTH - 1] = 0

      stop = min(TRIT_HASH_LENGTH, length-offset)
      trits[offset:offset+stop] = trits_from_hash[0:stop]

      flipped_bytes = bytearray(conv.convert_sign(~b) for b in unsigned_hash)

      # Reset internal state before feeding back in
      self.reset()
      self.k.update(flipped_bytes)

      offset += TRIT_HASH_LENGTH