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From "Kristian Waagan (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-3781) PositionedStoreStream.reposition(pos) with pos greater than length leaves the stream object in an inconsistent state
Date Wed, 16 Jul 2008 07:15:31 GMT

     [ https://issues.apache.org/jira/browse/DERBY-3781?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Kristian Waagan updated DERBY-3781:

    Attachment: derby-3781-2a-remove_convenience_link.diff

'derby-3781-2a-remove_convenience_link.diff' removes the convenience link and replaces it
with casts in three places. I also added a instanceof check in the constructor to detect where
in the code an invalid stream might be passed in.
I think it is better to catch the error where it originates instead of waiting for a ClassCastException
at a later point in time.

Patch ready for review.

> PositionedStoreStream.reposition(pos) with pos greater than length leaves the stream
object in an inconsistent state
> --------------------------------------------------------------------------------------------------------------------
>                 Key: DERBY-3781
>                 URL: https://issues.apache.org/jira/browse/DERBY-3781
>             Project: Derby
>          Issue Type: Bug
>          Components: Store
>    Affects Versions:,,
>            Reporter: Kristian Waagan
>            Assignee: Kristian Waagan
>            Priority: Minor
>             Fix For:
>         Attachments: derby-3781-1a-fix_and_test.diff, derby-3781-2a-remove_convenience_link.diff
> PositionedStoreStream.reposition(pos) with pos greater than the stream length leaves
the stream object in an inconsistent state, causing subsequent calls to fail or the state
to remain inconsistent (which can cause the wrong data to be returned).
> The problem is that the position variable gets out of sync with the underlying stream.
> There are at least two ways to fix this (assuming the positioned store stream does not
know the length of the underlying stream):
>  a) Reset stream to position zero.
>  b) Let the stream be positioned at EOF and update the internal position variable.
> Option b) leaves the stream in an unusable state, and the next request will cause option
a) to be performed. It also require a slight rewrite of 'PositionedStoreStream.skipFully'
and 'PositionedStoreStream.reposition' to be able to determine the position of the stream
(the length in this case).
> Option a) will cause the first page of the stream to be read into the cache (if not already
there), but taken the reason for doing this is an error condition it seems acceptable.
> A correct value of the position variable is required for correct/valid operation of PositionedStoreStream.

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