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https://issues.apache.org/jira/browse/NIFI-3495?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15871056#comment-15871056
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ASF GitHub Bot commented on NIFI-3495:
--------------------------------------

GitHub user olegz opened a pull request:

    https://github.com/apache/nifi/pull/1518

    NIFI-3495 fixed the index issue with TextLineDemarcator

    Thank you for submitting a contribution to Apache NiFi.
    
    In order to streamline the review of the contribution we ask you
    to ensure the following steps have been taken:
    
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You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/olegz/nifi NIFI-3495

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/nifi/pull/1518.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1518
    
----
commit d65ceef58adc448cfa321411d5f4651459063e1c
Author: Oleg Zhurakousky <[email protected]>
Date:   2017-02-17T02:05:59Z

    NIFI-3495 fixed the index issue with TextLineDemarcator

----


> TextLineDemarcator sets the wrong index when read ahead is performed in isEol 
> operation
> ---------------------------------------------------------------------------------------
>
>                 Key: NIFI-3495
>                 URL: https://issues.apache.org/jira/browse/NIFI-3495
>             Project: Apache NiFi
>          Issue Type: Bug
>            Reporter: Oleg Zhurakousky
>            Assignee: Oleg Zhurakousky
>            Priority: Critical
>             Fix For: 1.2.0
>
>
> This condition is very rare. It only occurs when read ahead (call to 
> _fill()_)  is made inside of the _isEol_ operation which essentially sets the 
> new index which then is reset inside of the main _nextOffsetInfo_ operation. 
> So the fix is to basically monitor if _isEol_ had to perform read ahead and 
> if it did do not reset the index.
> More details.
> While this component is modeled after standard Java BufferedReader which 
> simply reads and returns lines (delimited by CR or LF or both), this reader 
> also holds the information about how each line terminated (i.e., EOF, or CR 
> or LF or CR and LF) returning it to the caller as OffsetInfo. 
> So for example if you have a record "foo\r\nbar" and you read it with 
> BuffereReader you will get 'foo' and 'bar'. However you will not know that 
> between the two tokens there was CR and LF and therefore will not be able to 
> restore (if need to) the record to its original state. The TextLineDemarcator 
> will return OffsetInfo which holds the delimiter and other information.
> So, to accomplish the above every time we see CR (13) we need to peek at the 
> next byte and see if its LF(10). When at the end of the buffer such peek 
> becomes complicated since we need to read more data and so we did, but didn't 
> handle index properly essentially setting it back to the old value when the 
> new one was set inside of the fill().



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