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File Content: multibackend.rst

.. hazmat::

MultiBackend
============

.. currentmodule:: cryptography.hazmat.backends.multibackend

.. class:: MultiBackend(backends)

.. versionadded:: 0.2

This class allows you to combine multiple backends into a single backend
    that offers the combined features of all of its constituents.

.. testsetup::

from cryptography import utils
        from cryptography.exceptions import UnsupportedAlgorithm, _Reasons
        from cryptography.hazmat.backends.interfaces import HashBackend
        from cryptography.hazmat.backends.openssl.backend import backend as backend2

@utils.register_interface(HashBackend)
        class DummyHashBackend(object):
            def hash_supported(self, algorithm):
                return False

def create_hash_ctx(self, algorithm):
                raise UnsupportedAlgorithm("", _Reasons.UNSUPPORTED_HASH)

backend1 = DummyHashBackend()

.. doctest::

>>> from cryptography.hazmat.backends.multibackend import MultiBackend
        >>> from cryptography.hazmat.primitives import hashes
        >>> backend1.hash_supported(hashes.SHA256())
        False
        >>> backend2.hash_supported(hashes.SHA256())
        True
        >>> multi_backend = MultiBackend([backend1, backend2])
        >>> multi_backend.hash_supported(hashes.SHA256())
        True

:param backends: A ``list`` of backend objects. Backends are checked for
                     feature support in the order they appear in this list.

Name	Size	Permission
commoncrypto.rst	1068 bytes	0644
index.rst	841 bytes	0644
interfaces.rst	24790 bytes	0644
multibackend.rst	1510 bytes	0644
openssl.rst	5256 bytes	0644