hmac.py 文件源码

def __init__(self, key, algorithm, backend, ctx=None):
        if not isinstance(backend, HMACBackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement HMACBackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        if not isinstance(algorithm, hashes.HashAlgorithm):
            raise TypeError("Expected instance of hashes.HashAlgorithm.")
        self._algorithm = algorithm

        self._backend = backend
        self._key = key
        if ctx is None:
            self._ctx = self._backend.create_hmac_ctx(key, self.algorithm)
        else:
            self._ctx = ctx