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https://issues.apache.org/jira/browse/DERBY-4702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12879715#action_12879715
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Kristian Waagan commented on DERBY-4702:
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Comment copied from DERBY-1595 (:
a) DRDA vol 3, page 300 (17/Jun/10 05:11 AM):
"The length of the extended total length field must be a multiple of two
bytes, and it cannot be longer than necessary to express the length of the
object's data."
b) .../client/net/Request:
// according to Jim and some tests perfomred on Lob data,
// the extended length bytes are signed. Assume that
// if this is the case for Lobs, it is the case for
// all extended length scenarios.
It sounds reasonable to expect that the code never sends negative lengths,
but:
- negative values may be reserved for a special purpose
- the DRDA spec may have made a wrong turn in this area (i.e "wasting
space" by using signed instead of unsigned)
- since the client only sends signed positive values that are small enough
so that the most significant bit isn't used, the difference between client and
server doesn't cause problems
- if the server is correct, our client is breaking the spec for a series of
ranges of LOB lengths (point a, the client uses 0x7FFFL, 0x7FFFFFFF and
0x7FFFFFFFFFFF). This doesn't matter, as the server doesn't seem to enforce
point a.
(- btw, I haven't investigated if the extended length bytes are used when
transferring data from the server to the client)
To move on with the reported issue, I have logged DERBY-4702 to track further
discussion of this topic.
> Determine if the DRDA Layber B DSS extended total length field should carry a
> signed or unsigned integer
> --------------------------------------------------------------------------------------------------------
>
> Key: DERBY-4702
> URL: https://issues.apache.org/jira/browse/DERBY-4702
> Project: Derby
> Issue Type: Task
> Components: Network Client, Network Server
> Affects Versions: 10.7.0.0
> Reporter: Kristian Waagan
> Priority: Minor
>
> The client and the server disagrees on whether the extended total length
> field in the DRDA protocol is signed or unsigned.
> A search in the DRDA specification (version 4) was fruitless.
> I don't think the current situation results in any practical problems, but it
> would be nice to determine what the correct representation is and to make the
> client and the server consistent.
> This issue was brought up under DERBY-1595.
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