Hi,
If the 0x80 byte is taken as length rather than as value (as I have
taken in my interpretation of the bytes), then there is still a problem
with the byte stream, since the length of the result field here is 0x6,
not 0x8.
From Olivier Dubuisson's book, fields within a structure are implicitly
tagged. Making use of that here, the tag should not be put for the
'parameter' field. The only point of debate is whether I am correct or
not in deriving the length of the octet string as
(size of encoding for structure - number of bytes read so far)
If I am wrong, then the size of the structure is wrongly given as 0x06.
If I am write, I would like to know how to handle the additional 2 bytes
filled with 0 that are a part of the ReturnResult structure encoding.
Hope what I've written makes some sense.
Btw, if I look at the intention of the tool that's sending me this byte
stream, then the decoding that's happening is correct, except for the
handling of those 2 bytes.
Regds,
Divya
PS: To reiterate, the decoding I am doing is as follows:
0xa2: Tag for ReturnResult structure within Component (CNTX, CONS, 2)
0x0d: Length of the contents = 13 bytes
0x02: Integer tag (for invokeID)
0x01: Length of the contents = 1 byte
0x00: Value of invokeID = 0
0x30: Sequence tag (for result)
0x06: Length of the contents = 6 bytes
0x02: Integer tag (for localValue within operationCode)
0x01: Length of the contents = 1 byte
0x0e: Value of localValue = 0x0e
Assumed tag (UNIV, PRIM, OCTETSTRING_TAG_CODE) and length of
6 - 3 = 3 bytes
0x80: parameter[0]
0x01: parameter[1]
0x04: parameter[2]
The structure I am looking at is Component, where it is defined as:
Component ::= CHOICE {
invoke [1] IMPLICIT Invoke,
returnResultLast [2] IMPLICIT ReturnResult,
returnError [3] IMPLICIT ReturnError,
reject [4] IMPLICIT Reject,
returnResultNotLast [7] IMPLICIT ReturnResult
}
ReturnResult ::= SEQUENCE {
invokeID INTEGER (-128..127),
result SEQUENCE {
operationCode CHOICE {
localValue INTEGER,
globalValue OBJECT IDENTIFIER
},
parameter OCTET STRING (SIZE(1..255))
} OPTIONAL
}
Vishal wrote ---
> Hi Divya,
>
>
>
> The 2 null bytes (0x00) at the end are, may be, indicating end of contents
> for some parameter.
>
> Are you sure there is no length field for some parameter, before the
> bytes
> you have sent, in which length is specified as EOC-encoded.
>
>
>
> Thanks and Best Regards,
>
> Vishal.
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