For discussion at next WG call.
Regards
Steve Hanson
Architect, IBM Data Format Description Language (DFDL)
Co-Chair, OGF
DFDL Working Group
IBM SWG, Hursley, UK
smh@uk.ibm.com
tel:+44-1962-815848
----- Forwarded by Steve
Hanson/UK/IBM on 23/08/2013 16:20 -----
From:
Alex Wood1/UK/IBM
To:
Steve Hanson/UK/IBM@IBMGB,
Mark Frost/UK/IBM@IBMGB, dfdl-wg@ogf.org,
Date:
23/08/2013 14:58
Subject:
dfdl:lengthKind='prefixed'
, different encodings for prefix and content where prefixIncludesPrefixLength
is ‘yes.
Hi All,
Considering a case similar to that excluded
by errata 2.76. An element with lengthKind 'prefixed'
and prefixIncludesPrefixLength 'true' but where the prefix type and
the element both have lengthUnits 'characters' but have different encodings
(or specifically encodings with different lengths of characters).
I believe the issue that 2.76 is trying to avoid is the
issue of determining the length value in say characters when the prefix
contains no characters.
I am wondering if there is also a slightly subtler issue
when we are calculating a length in characters but where a part of the
length is in a different encoding from the other.
For example the prefix contains 2 UTF16 (2 byte) characters
and the content contains 2 UTF32 (4 byte) characters..
Do we just quote a length in characters regardless of
encoding. eg. 4 characters. Or is this confusing ....
2.76
.
Section 12.3.4
. When property prefixIncludesPrefixLength is ‘yes’there
are some restrictions that need to be added to enable reliable lengths
to be calculated:
o If the
prefix type is lengthKind 'implicit' or 'explicit' then the lengthUnits
properties of
both the prefix type and the element must be the same.
Kind Regards,
- Alex
Alex Wood -
Software Engineer -
WebSphere Message Broker Development
IBM DFDL Development
MP 211, IBM UK Labs, Hursley Park, Winchester, Hants. SO21 2JN.
Tel: Internal 246272, External 01962 816272
Notes: Alex Wood1/UK/IBM@IBMGB
e-mail: wooda@uk.ibm.com
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