Thanks for the reply.
Now it is clear to me that I will use the context-specific Tags
instead of the Universal Tags in SEQUENCE OF.
Is the Tag 0x30 at the begining of the MY_PROJ Module means
that I can use Universal Tag of SEQUENCE for "A" because only the components
"A ::= SEQUENCE" is using AUTOMATIC TAG.
Is it correct?
On Thu, 29 Jan 2004 14:22:37 +0530
"Ramaswamy R - CTD, Chennai." <[EMAIL PROTECTED]> wrote:
> Hi,
> I am not quite sure if I understood the problem but here is my
> explanation. When AUTOMATIC Tagging is used the type specified in the
> SEQUENCE OF is not tagged (i.e. it does not become something like the 1st
> element of the SEQUENCE OF has tag 1, second 2 and so on). This seem to be
> the basis for the Encoded Data 2 (where the 1st element of the sequence of
> says [0] and second [1].
> In our case for each element of SEQUENCE OF B the tag used is that of B
> (in this case corresponding to that of a SEQUENCE - 30). As such all
> elements withing the value field of SEQUENCE OF B, will have tag 30. If the
> definition of B were
>
> B ::= [0] SEQUENCE {
> c [0] INTEGER,
> d [1] OCTET STRING
> }
>
> then the encoded data would have been
>
> 30 1B /* A ::= SEQUENCE */
> 80 01 01 /* a INTEGER */
> A1 16 /* b SEQUENCE OF
> B*/
> A0 09 /* B ::= SEQUENCE */
> 80 01 01 /* c INTEGER */
> 81 04 01 02 03 04 /* d OCTET STRING */
> A0 09 /* B ::= SEQUENCE */
> 80 01 01 /* c INTEGER */
> 81 04 01 02 03 04 /* d OCTETSTRING */
>
> An easy way to remember this is that AUTOMATIC tagging affects only the
> representation itself (i.e. an ASN.1 spec can be generated with the tags).
> ASN.1 does not allow specifying tag for each member of a SEQUENCE OF or SET
> OF. So AUTOMATIC tagging does not affect the same. Hope this explains
> things.
>
> Regd
> SamY
> (Ramaswamy)
>
> -----Original Message-----
> From: Raymond Javier [mailto:[EMAIL PROTECTED]
> Sent: Thursday, January 29, 2004 1:21 PM
> To: [EMAIL PROTECTED]
> Subject: [ASN.1] Tag of SEQUENCE OF if AUTOMATIC Tagging
>
>
> Hi,
>
> I am confused on Tagging when SEQUENCE OF is used
>
> I have the following ASN.1 BER definition:
>
> MY_PROJ DEFINITIONS AUTOMATIC TAGS ::=
>
> BEGIN
>
> A ::= SEQUENCE {
> a [0] INTEGER,
> b [1] SEQUENCE OF B
> }
>
> B ::= SEQUENCE {
> c [0] INTEGER,
> d [1] OCTET STRING
> }
>
> END
>
> Encoded Data 1.
> 30 1B /* A ::= SEQUENCE */
> 80 01 01 /* a
> INTEGER */
> A1 16 /* b
> SEQUENCE OF B*/
> 30 09 /* B ::= SEQUENCE */
> 80 01 01 /* c
> INTEGER */
> 81 04 01 02 03 04 /* d OCTET
> STRING */
> 30 09 /* B ::= SEQUENCE */
> 80 01 01 /* c
> INTEGER */
> 81 04 01 02 03 04 /* d OCTET
> STRING */
>
>
> Encoded Data 2.
> 30 1B /* A ::= SEQUENCE */
> 80 01 01 /* a
> INTEGER */
> A1 16 /* b
> SEQUENCE OF B*/
> A0 09 /* B ::= SEQUENCE */
> 80 01 01 /* c
> INTEGER */
> 81 04 01 02 03 04 /* d OCTET
> STRING */
> A1 09 /* B ::= SEQUENCE */
> 80 01 01 /* c
> INTEGER */
> 81 04 01 02 03 04 /* d OCTET
> STRING */
>
>
> Which encoded data is correct?
