ZIP entry copy without recompression

[Seán Coffey]

I think that's a fine idea Eirik. Definitely has its use cases like you 
mention.

Some jarsigner operations would also benefit from this. I've created 
https://bugs.openjdk.org/browse/JDK-8303960 to track it.

regards,
Sean.

On 31/01/2023 23:41, Lance Andersen wrote:
> I have not add a chance to look or think about this yet but wanted to 
> know I will
>
>> On Jan 19, 2023, at 2:03 PM, Eirik Bjørsnøs <eirbjo at gmail.com> wrote:
>>
>> Hi,
>>
>> A common use case for java.util.zip in build tools involves copying
>> entries from a ZipFile or ZipInputStream to a ZipOutputStream without
>> actually modifying the data.
>>
>> Example use cases include minification (make a JAR with only the
>> reachable classes) and merging (combine several JAR files into one
>> uberjar).
>>
>> Inflating an entry just to immediately deflate it again with no
>> modifications seems wasteful.
>>
>> The following draft PR introduces
>> ZipFileInflaterInputStream.transferTo which copies compressed ZipFile
>> data directly to ZipOutputStream's raw data stream:
>>
>> https://github.com/openjdk/jdk/pull/12099
>>
>> I'm typically seeing a 15 X improvement when copying xalan.jar to a
>> ZipOutputStream backed by a buffered FileOutputStream, or 22 X when
>> backed by OutputStream.nullOutputStream().
>>
>> The PR current stays completely on the happy path and is mostly there
>> to experiment and to show the potential performance benefits. There is
>> currently not much focus on validation or correctness. Copying files
>> to a different path is not supported, neither is copying from a
>> ZipInputStream.
>>
>> I initially considered creating new methods for raw copies, but opted
>> to minimize changes to public APIs, that's why I'm overriding
>> transferTo.
>>
>> The PR is not intended for regular review, but as a starting point for
>> a discussion about the usefulness of the idea and the general solution
>> space. If we can reach consensus on such a discussion, I'll probably
>> be happy to work on a more complete PR.
>>
>> Cheers,
>> Eirik.
>
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> Lance Andersen | Principal Member of Technical Staff | +1.781.442.2037
> Oracle Java Engineering
> 1 Network Drive
> Burlington, MA 01803
> Lance.Andersen at oracle.com
>
>
>
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