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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Work logged] (IMAGING-220) JpegDecoder takes a long time (+10s) to decode a bad JPEG
Date Tue, 08 Jan 2019 07:10:00 GMT

     [ https://issues.apache.org/jira/browse/IMAGING-220?focusedWorklogId=182200&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-182200
]

ASF GitHub Bot logged work on IMAGING-220:
------------------------------------------

                Author: ASF GitHub Bot
            Created on: 08/Jan/19 07:09
            Start Date: 08/Jan/19 07:09
    Worklog Time Spent: 10m 
      Work Description: kinow commented on pull request #40: IMAGING-220: replace while by
if in the JPEG decoder extend method
URL: https://github.com/apache/commons-imaging/pull/40
 
 
   
 
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Issue Time Tracking
-------------------

    Worklog Id:     (was: 182200)
    Time Spent: 20m  (was: 10m)

> JpegDecoder takes a long time (+10s) to decode a bad JPEG
> ---------------------------------------------------------
>
>                 Key: IMAGING-220
>                 URL: https://issues.apache.org/jira/browse/IMAGING-220
>             Project: Commons Imaging
>          Issue Type: Bug
>            Reporter: Bruno P. Kinoshita
>            Assignee: Bruno P. Kinoshita
>            Priority: Major
>             Fix For: 1.0
>
>         Attachments: Screenshot from 2019-01-02 21-02-41.png, timeout-48eb4251935b4ca8b26d1859ea525c1b42ae0c78
>
>          Time Spent: 20m
>  Remaining Estimate: 0h
>
> Debugging the code I suspected there was something weird, as it would stay a long time
in the while look as a += operation had no effect. Then looked up for the extend and section
number.
> The extend method in the JpegDecoder is using a while instead of an if. If you look at
the specification, it is not clear whether it is an if or while, but it looks to me like it
is a simple if condition.
> Furthermore, if you look at the following examples, it is possible to confirm others
implemented the bit extension method with a simple if.
>  * [https://github.com/libjpeg-turbo/libjpeg-turbo/blob/9bc8eb6449a32f452ab3fc9f94af672a0af13f81/jdphuff.c#L204]
>  * [https://github.com/lifthrasiir/rust-image/blob/ee0e7064d96a1015650481b7046420e6238cf53d/src/jpeg/decoder.rs#L681]
> This does not occur in Sanselan as there is JpegDecoder and no extend method as well.
Attaching example file that takes over 10 seconds to be processed (up to the point where the
decoder throws an exception actually).



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