Re: [ASN1] BER encoding of

[Lev Walkin]

Banibrata Dutta wrote:

Hi Lev,

Since the inner SEQUENCE doesn't have a tag (as I'd written atleast), how
are the 2 SEQUENCE occurances unambiguated!

They don't need to be.

The outer SEQUENCE OF comprises of zero or more (if unrestricted)
occurences of inner SEQUENCE, in that specific order. So it's more like
a list, or an ordered collection of certain formatted (hence, SEQUENCE)
information blocks. There is no differentiation between them, except
for the relative position of a particular SEQUENCE inside a chain of
them.

Cheers,
- bdutta

-----Original Message-----

From: Lev Walkin [mailto:[EMAIL PROTECTED] Sent: Tuesday, June 14, 2005 11:53 PM

To: Banibrata Dutta
Cc: asn1@asn1.org
Subject: Re: [ASN1] BER encoding of

Banibrata Dutta wrote:

Hi Lev,

Thanks for the clarification. Also, could you just give an example of what would the BER encoded stream look like, if instead of SIZE(1) we had a

SIZE(2) SEQUENCE OF ? I am confused on whether it should be:-

[6] {
 SEQUENCE {
 }
 SEQUENCE {
 }
}

Yes.

Or be:-

[6] {
 SEQUENCE {
 }
}
[6] {
 SEQUENCE {
 }
}

No.

Thanks,
bdutta

-----Original Message-----
From: Lev Walkin [mailto:[EMAIL PROTECTED]
Sent: Tuesday, June 14, 2005 11:27 PM
To: Banibrata Dutta
Cc: asn1@asn1.org
Subject: Re: [ASN1] BER encoding of

Banibrata Dutta wrote:

Hi,

Could someone please verify that for the following ASN.1 definitions
(snippet) :-

  contact [6] IMPLICIT SEQUENCE SIZE(1..5) OF SEQUENCE {
          name  [0] IMPLICIT Name OPTIONAL,
          url   [1] EXPLICIT Url OPTIONAL,
          value [2] IMPLICIT INTEGER OPTIONAL,
          delta [5] IMPLICIT INTEGER OPTIONAL
      } OPTIONAL,


Name ::= IA5String (SIZE(1..64))

Url ::= CHOICE {
  myUrl       [0] IMPLICIT SEQUENCE {
      user     [0] IMPLICIT IA5String (SIZE(1..16)) OPTIONAL,
      host     [1] IMPLICIT IA5String (SIZE(1..64)) OPTIONAL,
      port     [2] IMPLICIT INTEGER OPTIONAL,
      transport   [3] IMPLICIT ENUMERATED {
          udp(0),
          tcp(1),
      } OPTIONAL
  }

Is the following BER encoding of "contact" field is correct ?

[6] {
  SEQUENCE {
    [0] (72 65 73 70 6F 6E 73 65 4F 4B)
    [2] (00)
  }

Yes, this is correct. It translates to a value of the
following:

        contact [6] IMPLICIT SEQUENCE SIZE(1) OF SEQUENCE {
                name [0] IMPLICIT IA5String (SIZE(10)),
                value [2] IMPLICIT INTEGER (0)
        }

and how about this ?

[6] {
  SEQUENCE {
    [1] {
      [0] {
        [1] (6C 61 76)
        [2] (16 44)
        [3] (00)
      }
    }
    [1] {
      [0] {
        [1] (6C 61 76)
        [2] (16 45)
        [3] (01)
      }
    }
  }
}

This one is not correct. There are two tags [1] inside the SEQUENCE (which is inside the outer SEQUENCE OF), which is wrong.

--
Lev Walkin
[EMAIL PROTECTED]

--
Lev Walkin
[EMAIL PROTECTED]

--
Lev Walkin
[EMAIL PROTECTED]
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