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From "Knut Anders Hatlen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3770) Create a utility class for skipping data in an InputStream
Date Mon, 01 Sep 2008 14:54:44 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3770?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12627475#action_12627475
] 

Knut Anders Hatlen commented on DERBY-3770:
-------------------------------------------

Thank you!

The patch looks good to me. I have started the regression tests and plan to commit it if there
aren't any failures.

Some small things that we may consider to change after the commit:

  1) Should the test be placed under unitTests/junit instead of functionTests/tests/engine?
The existing tests under functionTests/tests/engine seems to boot the full Derby engine, whereas
the test in the patch only tests a single internal class and probably fits better under unitTests/junit.

  2) In skipUntilEOF, the scope of the local variable r could be narrowed down (it could be
declared in the body of the while loop).

> Create a utility class for skipping data in an InputStream
> ----------------------------------------------------------
>
>                 Key: DERBY-3770
>                 URL: https://issues.apache.org/jira/browse/DERBY-3770
>             Project: Derby
>          Issue Type: Improvement
>          Components: Miscellaneous
>    Affects Versions: 10.5.0.0
>            Reporter: Kristian Waagan
>            Assignee: Junjie Peng
>            Priority: Minor
>         Attachments: derby-3770-1.patch, derby-3770-1.stat, derby-3770-2.patch, derby-3770-2.stat,
derby-3770-3.patch, derby-3770-3.stat, derby-3770-4.patch, derby-3770-4.patch, derby-3770-4.stat,
derby-3770-4.stat, derby-3770-5.patch, derby-3770-5.stat
>
>
> The contract of InputStream.skip is somewhat difficult, some would even say broken.
> See http://java.sun.com/javase/6/docs/api/java/io/InputStream.html#skip(long))
> A utility class should be created to ensure that we use the same skip procedure throughout
the Derby code base.
> Suggested functionality:
>  - long skipFully(InputStream) : skips until EOF, returns number of bytes skipped
>  - void skipFully(InputStream,long) : skips requested number of bytes, throws EOFException
if there is too few bytes in the stream
> I know of two different approaches, both skipping in a loop:
>  a) Verify EOF with a read call when skip returns zero.
>  b) Throw EOFException if skip returns zero before requested number of bytes have been
skipped.
> There's related code in iapi.util.UTF8Util. Maybe this class, say StreamUtil, could be
put in the same package?

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