text: # This file is dual licensed under the terms of the Apache License, Version
  # 2.0, and the BSD License. See the LICENSE file in the root of this repository
  # for complete details.
  
  from __future__ import absolute_import, division, print_function
  
  
  from cryptography import utils
  from cryptography.exceptions import (
      AlreadyFinalized, UnsupportedAlgorithm, _Reasons
  )
  
  
  class Poly1305(object):
      def __init__(self, key):
          from cryptography.hazmat.backends.openssl.backend import backend
          if not backend.poly1305_supported():
              raise UnsupportedAlgorithm(
                  "poly1305 is not supported by this version of OpenSSL.",
                  _Reasons.UNSUPPORTED_MAC
              )
          self._ctx = backend.create_poly1305_ctx(key)
  
      def update(self, data):
          if self._ctx is None:
              raise AlreadyFinalized("Context was already finalized.")
          utils._check_byteslike("data", data)
          self._ctx.update(data)
  
      def finalize(self):
          if self._ctx is None:
              raise AlreadyFinalized("Context was already finalized.")
          mac = self._ctx.finalize()
          self._ctx = None
          return mac
  
      def verify(self, tag):
          utils._check_bytes("tag", tag)
          if self._ctx is None:
              raise AlreadyFinalized("Context was already finalized.")
  
          ctx, self._ctx = self._ctx, None
          ctx.verify(tag)
  