4813885: RFE: GZIPOutputStream should implement flush using Z_SYNC_FLUSH

[Martin Buchholz]

On Thu, May 13, 2010 at 00:11, Xueming Shen <xueming.shen at oracle.com> wrote:
> Martin Buchholz wrote:
>>
>> On Wed, May 12, 2010 at 23:46, Xueming Shen <xueming.shen at oracle.com>
>> wrote:
>>
>>>
>>> Thanks for the review.
>>>
>>> The Z_SYNC_FLUSH is supposed to fully replace the Z_PARTIAL_FLUSH.
>>>
>>> We concluded last round that Z_SYNC_FLUSH is enough for the "high-level"
>>> DOS, as well as the GZIPOS, use Deflater directly if  more needed. I hope
>>> you
>>> are not suggesting we go back to redo the flush to int.
>>>
>>
>> Maybe we should.
>>
>> http://www.jcraft.com/jzlib/
>>
>> """
>> To implement this functionality, the Z_PARTIAL_FLUSH mode of zlib must
>> be used, however JDK does not permit us to do so. It seems that this
>> problem has been well known and some people have already reported to
>> JavaSoft's BugParade(for example, BugId:4255743), but any positive
>> response has not been returned from JavaSoft, so this problem will not
>> be solved forever. This is our motivation to hack JZlib.
>> """
>>
>>
>
> I thought I had closed this one (#4255743) as the dup of #4206909.
>
> This is actually why we did 4206909 and now doing #4813885. With the fix for
> #4206909, you no
> longer need jzlib:-) Yes, we use Z_SYNC_FLUSH, not Z_PARTIAL_FLUSH because
> the later is going
> away, replaced by Z_SYNC_FLUSH. They are the same thing.

I can't say that I really understand the difference, but...

The description of the different flush modes in zlib.h
clearly distinguishes between Z_SYNC_FLUSH and
Z_PARTIAL_FLUSH.

Z_PARTIAL_FLUSH is clearly undeprecated in zlib 1.2.5

"""- Remove deprecation comment on Z_PARTIAL_FLUSH (it stays)"""

So I remain unconvinced, but I'm not going to push on this any more,
or at least not until I understand it better.

Martin

> So with #4206909 and #4813885 you can now  sync_flush the GZIPOutputStream
> and
> DeflaterOutputStream, as needed by the "functionality" mentioned in jzlib.
>
> Sherman
>
>
>