hashes.py 文件源码

def __init__(self, backend, algorithm, ctx=None):
        self._algorithm = algorithm
        self._backend = backend

        if ctx is None:
            try:
                methods = self._backend._hash_mapping[self.algorithm.name]
            except KeyError:
                raise UnsupportedAlgorithm(
                    "{0} is not a supported hash on this backend.".format(
                        algorithm.name),
                    _Reasons.UNSUPPORTED_HASH
                )
            ctx = self._backend._ffi.new(methods.ctx)
            res = methods.hash_init(ctx)
            assert res == 1

        self._ctx = ctx