[pyasn1-users] (no subject)

[Nikolay N. <nik...@gm...>]

Hi,

I am trying to create a new module for 3gpp 32.298 MMTel CDR.

I have started experimenting with simple definition:
DEFINITIONS IMPLICIT TAGS ::=
BEGIN
-- EXPORTS everything

MMTelRecord ::= SET
{
recordType  [0] RecordType,
retransmission [1] NULL OPTIONAL,
sIP-Method  [2] SIP-Method OPTIONAL,
role-of-Node  [3] Role-of-Node OPTIONAL
}

RecordType ::= INTEGER
{
--  Record Value 83 is MMTel specific.
--  The contents are defined in TS 32.275 [35]
--
mMTelRecord (83)
}

SIP-Method ::= GraphicString

Role-of-Node ::= ENUMERATED
{
originating (0),
terminating (1)
}
END


and description of the definition in with pyasn1 that I have created is:

from pyasn1.type import univ, namedtype, tag, char, namedval, constraint

'''
Test to encode and decoder IMS MMTel CDR ber files
Using just a subset of MMTelRecord ASN1 definition defined in 3GPP TS 32.298
'''

MAX = 64


class RecordType(univ.Integer):
    namedValues = namedval.NamedValues(
        ('mMTelRecord', 83)
    )


class SIPMethod(char.GraphicString): pass


class RoleOfNode(univ.Enumerated):
    namedValues = namedval.NamedValues(
        ('originating', 0),
        ('terminating', 1)
    )
    subtypeSpec = univ.Enumerated.subtypeSpec +
constraint.SingleValueConstraint(0, 1)


class MMTelRecord(univ.Set):
    componentType = namedtype.NamedTypes(
        namedtype.NamedType('recordType',

RecordType().subtype(implicitTag=tag.Tag(tag.tagClassContext,
tag.tagFormatSimple, 0))),
        namedtype.OptionalNamedType('retransmission', univ.Null().subtype(
            implicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 1))),
        namedtype.OptionalNamedType('sIP-Method',
                                    SIPMethod().subtype(

implicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 2))),
        namedtype.OptionalNamedType('role-of-Node',
                                    RoleOfNode().subtype(

implicitTag=tag.Tag(tag.tagClassContext, tag.tagFormatSimple, 3))),
    )


class MMTelRecords(univ.SetOf):
    componentType = MMTelRecord()
    sizeSpec = univ.SetOf.sizeSpec + constraint.ValueSizeConstraint(1, MAX)


Here is how I try encode and write the ber file:

#!/usb/bin/python

from pyasn1.codec.ber import encoder, decoder

from modules import mmtel3gpp32298 as mmtel

from time import sleep


'''
Test to encode and decoder IMS MMTel CDR ber files
Using just a subset of MMTelRecord ASN1 definition defined in 3GPP TS 32.298
'''


def cdr_write(file):

    records = mmtel.MMTelRecords()

    for i in range(0,1):
        print "Start of cdr log: " + str(i)
        record = mmtel.MMTelRecord()
        records.setComponentByPosition(i,
record.setComponentByPosition(0, mmtel.RecordType(83), ''))
        records.setComponentByPosition(i,
record.setComponentByPosition(2, mmtel.SIPMethod('INVITE'), ''))
        records.setComponentByPosition(i,
record.setComponentByPosition(3, mmtel.RoleOfNode(0), ''))

        # print record.prettyPrint()
        print str(record)
        print "End of cdr log: " + str(i)

    sleep(2)

    w_data = encoder.encode(records)
    print w_data

    # print "Filename: " + file
    with open(file, 'wb') as f:
        # f.write(w_data)
        f.write(w_data)
        f.close

def cdr_read(file):
    with open(file, 'rb') as f:
        r_data = f.read
        f.close()
        data = decoder.decode(r_data, asn1Spec=mmtel.MMTelRecord)

        print data


if __name__ == "__main__":

    file = 'mcdr2.ber'
    cdr_write(file)
    cdr_read(file)

###########

Ber file is created but cannot it cannot be decoded:

Traceback (most recent call last):
  File "C:/Users/nnenchev/PycharmProjects/mmtel-cdrs/mmtel.py", line
57, in <module>
    cdr_read(file)
  File "C:/Users/nnenchev/PycharmProjects/mmtel-cdrs/mmtel.py", line
46, in cdr_read
    data = decoder.decode(r_data, asn1Spec=mmtel.MMTelRecord)
  File "C:\Python27\lib\site-packages\pyasn1-0.1.7-py2.7.egg\pyasn1\codec\ber\decoder.py",
line 600, in __call__
pyasn1.error.PyAsn1Error: Bad octet stream type



If I compare hexdump of the produced ber file with one created from
asn1 studio from OSS Nokalva, seems that my ber file is not correct.

Ber file from asn1studio

$ xxd.exe MMTelRecord.ber
0000000: 310e 8001 5382 0649 4e56 4954 4583 0100  1...S..INVITE...

Ber file procudes with python script above.

$ xxd.exe mcdr2.ber
0000000: 3110 310e 0201 5319 0649 4e56 4954 450a  1.1...S..INVITE.
0000010: 0100


Can you please advise what I am doing wrong?


BR

Nikolay