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#
# This file is part of pyasn1 software.
#
# Copyright (c) 2005-2017, Ilya Etingof <etingof@gmail.com>
# License: http://pyasn1.sf.net/license.html
#
from pyasn1.type import univ
from pyasn1.codec.cer import decoder
__all__ = ['decode']
class BitStringDecoder(decoder.BitStringDecoder):
supportConstructedForm = False
class OctetStringDecoder(decoder.OctetStringDecoder):
supportConstructedForm = False
# TODO: prohibit non-canonical encoding
RealDecoder = decoder.RealDecoder
tagMap = decoder.tagMap.copy()
tagMap.update(
{univ.BitString.tagSet: BitStringDecoder(),
univ.OctetString.tagSet: OctetStringDecoder(),
univ.Real.tagSet: RealDecoder()}
)
typeMap = decoder.typeMap.copy()
# Put in non-ambiguous types for faster codec lookup
for typeDecoder in tagMap.values():
if typeDecoder.protoComponent is not None:
typeId = typeDecoder.protoComponent.__class__.typeId
if typeId is not None and typeId not in typeMap:
typeMap[typeId] = typeDecoder
class Decoder(decoder.Decoder):
supportIndefLength = False
#: Turns DER octet stream into an ASN.1 object.
#:
#: Takes DER octetstream and decode it into an ASN.1 object
#: (e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative) which
#: may be a scalar or an arbitrary nested structure.
#:
#: Parameters
#: ----------
#: substrate: :py:class:`bytes` (Python 3) or :py:class:`str` (Python 2)
#: DER octetstream
#:
#: asn1Spec: any pyasn1 type object e.g. :py:class:`~pyasn1.type.base.PyAsn1Item` derivative
#: A pyasn1 type object to act as a template guiding the decoder. Depending on the ASN.1 structure
#: being decoded, *asn1Spec* may or may not be required. Most common reason for
#: it to require is that ASN.1 structure is encoded in *IMPLICIT* tagging mode.
#:
#: Returns
#: -------
#: : :py:class:`tuple`
#: A tuple of pyasn1 object recovered from DER substrate (:py:class:`~pyasn1.type.base.PyAsn1Item` derivative)
#: and the unprocessed trailing portion of the *substrate* (may be empty)
#:
#: Raises
#: ------
#: : :py:class:`pyasn1.error.PyAsn1Error`
#: On decoding errors
decode = Decoder(tagMap, typeMap)