Re: H.245 OCTET STRINGs

18 Feb 1998

      Jim,
I think it is just a matter of compiler options.
We are using the OSS tools. If no options are set, there are many such
warnings, and the resulting H.245 structure is about 32 Mbytes. This
seems to be because by default all parts of the structure (except object
IDs) are included, as specified, in a union.
To eliminate the warnings and reduce the structure size to something
manageable we have used the options
--<LINKED SET OF, SEQUENCE OF , OCTET STRING>--
This causes the compiler to create a structure with pointers to objects
rather than a structure with the objects included directly.
Best regards
Mike
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* Mike Nilsson                     Tel:   +44 1473 645413              *
* Video Processing Unit            Fax:   +44 1473 643791              *
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...

From:  Jim Toga[SMTP:jtoga@jf.intel.com]
Sent:  17 February 1998 21:44
To:    itu-sg16@mailbag.jf.intel.com
Cc:    mike.nilsson@BT-SYS.BT.CO.UK; dskran@ascend.com;
mreid@videoserver.com
Subject:       H.245 OCTET STRINGs
It has come to my attention that there are a number of OCTET STRINGS
defined in H.245 along the lines of
  "h235Key                OCTET STRING (SIZE(1..65535))"

  "value          OCTET STRING (SIZE(1..65535))"

          "certificateResponse            OCTET STRING (SIZE(1..65535))

OPTIONAL"
The problem with these difinitions is that with the terminating NULL (
I
think...) the lentgh goes over by one byte, a 64k block of data.   The
OSS
compiler generates the following warning, which goes away if we change
the
lenth to '65534'....
"h245.asn", line 1941 (MULTIMEDIA-SYSTEM-CONTROL): C0470W: The size of
the
generated C structure for the SET OF or SEQUENCE OF exceeds 64K bytes
and may
adversely affect CPU and memory performance.  Consider use of the
LINKED or
UNBOUNDED directive.
Comments?....fixes?......
jimt.

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Mike Nilsson

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