[jira] Updated: (HARMONY-6637) [classlib] [archive] Inflater.inflate() short-circuits on zero-length request, finished() never true for a zero-length data source

["Roberto Tyley (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HARMONY-6637?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Roberto Tyley updated HARMONY-6637:
-----------------------------------

    Attachment: Main.java

This file demonstrates the difference between Harmony and the RI for java.util.zip.Inflater

The RI output is:

Inflating 10 bytes in a loop... [ 10 ] ...read total 10 bytes
Inflating 5 bytes in a loop... [ 5 ] ...read total 5 bytes
Inflating 0 bytes in a loop... [ 0 ] ...read total 0 bytes

The Harmony output is:

Inflating 10 bytes in a loop... [ 10 ] ...read total 10 bytes
Inflating 5 bytes in a loop... [ 5 ] ...read total 5 bytes
Inflating 0 bytes in a loop... [ 0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  0  ... forever



> [classlib] [archive] Inflater.inflate() short-circuits on zero-length request, finished() never true for a zero-length data source
> ----------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HARMONY-6637
>                 URL: https://issues.apache.org/jira/browse/HARMONY-6637
>             Project: Harmony
>          Issue Type: Bug
>          Components: Classlib
>            Reporter: Roberto Tyley
>            Priority: Critical
>         Attachments: Main.java
>
>
> There's code in the inflate() method of classlib/modules/archive/src/main/java/java/util/zip/Inflater.java (r926871 and earlier) which short-cuts the inflation if the parameter 'nbytes' is 0 - ie if the caller is actually requesting zero bytes:
> if (nbytes == 0) {
>      return 0;     --- Don't do any work: DON'T UPDATE THE *FINISHED* FLAG!
> }
> While it seems reasonable, it is in fact incompatible with the RI (which *does* attempt to process the deflated source data in the nbytes, and will update the finished() flag) - and so causes problems with a common inflation loop scenario, where the code loops to populate a destination byte-array of known size while inflater.finished() is not true. Even if the destination byte-array is known to be zero-length (e.g. we're deflating a zero-length file), the coder might still reasonably expect calling inflate() to set the finished() flag to true. However, unlike the RI, Harmony implementation does not update the finished() flag, which leads to an infinite loop or some other bad outcome.
> Bit short on time right now, will try to provide a better testcase and possibly a patch at a later date.
> best regards,
> Roberto Tyley

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