Hello Tong,
One extract from
********** ASN.1 Complete by Prof John Larmouth says
�� implicit tagging: (this is what has been described so far), where the new
tag over-rides the
old tag and type information which was carried by the old tag is now only
implicit in the
encoding; this cannot be allowed for a "CHOICE" type; and
�� explicit tagging: we add a new TLV wrapper specifically to carry the new
tag in the "T"
part of this wrapper, and carry the entire original TLV (with the old tag)
in the "V" part of this wrapper; clearly this is OK for "CHOICE".
***********
I don't think there is affection of IMPLICIT on the structure that was
quoted by you!
In the implicit env the encoding for the structrue
A ::= SEQUENCE{
b INTEGER -- variable name should start with a small
letter !
}
C A::={16}
If you expand C
C ::= SEQUENCE{
b INTEGER -- variable name should start with a small
letter !
}
Then the encoding should be
0x30 0x03 0x02 0x01 0x10
If you define C ::= INTEGER ...
then the BER encoding( for a value of 16 ) will be
0x02 0x01 0x10
Warm regards,
Vasa
-----Original Message-----
From: tong [mailto:[EMAIL PROTECTED]]
Sent: Friday, July 19, 2002 1:26 PM
To: [EMAIL PROTECTED]
Subject: [ASN.1] a doubt about IMPLICIT
Hi all
Is IMPLICIT only mean that: When several Tags express a same
parameter,then only use one tag to express the parameter?
Is this right?
and IMPLICIT don't have any affection on conditions like this:
A ::= SEQUENCE{
B INTEGER
}
C A::={16}
the encode of C is: 30 03 02 01 10 ,and is not :02 01 10 ?
