RFR(S): 8073497: Lazy conversion of ZipEntry time

[Claes Redestad]

Hi Sherman,

On 2015-02-21 19:49, Xueming Shen wrote:
> Hi Claes,
>
> This change basically undo the "fix" for 4759491 [1], for better 
> performance ...
>

my intent was never to break current behavior, but that mistake can be 
rectified
without missing out on the startup benefit of laziness:

http://cr.openjdk.java.net/~redestad/jdk9/8073497/webrev.1/

The time/mtime getters now use the mtime field if it exists, while the 
setters will
update both fields. Since getLastModified already fell back to 
converting the
time field rather than null if mtime wasn't set, setting mtime to a 
FileTime when
calling setTime seems consistent and a cheap way to preserve the time 
precision.

I guess a range check to skip the FileTime creation in setTime if the 
time is within
the DOS time bounds would be a valid optimization, since that will typically
always be the case.

> If we go with this change, I think we should also update the field 
> comment back to the
> original one to clearly indicates the "time" is "in DOS time".
>
> -    long time = -1;     // modification time (in DOS time)
> +    long mtime = -1;    // last modification time
>

Done.

>
> The set/getLastModifiedTime() pair also need update to set/get the 
> "time" field
> correctly to/from the dos time.

Done.

Thanks!

/Claes

>
> -Sherman
>
> [1] http://hg.openjdk.java.net/jdk8/jdk8/jdk/rev/90df6756406f
>
> On 2/21/15 6:34 AM, Claes Redestad wrote:
>> Hi all,
>>
>> please review this patch to re-introduce laziness in the java-to-dos 
>> time
>> conversions for the ZipEntry.time field.
>>
>> Webrev: http://cr.openjdk.java.net/~redestad/jdk9/8073497/webrev.0/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8073497
>>
>> See bug for more details.
>>
>> This behavior was actually the case before 8-b94, when the time field
>> was removed in favor of a set of FileTime fields, but when it was later
>> re-introduced to address some compatibility issues the conversion was
>> implemented in an eager fashion. This inadvertently affects VM startup
>> ever so little, since for every entry read via a ZipFile or 
>> ZipInputStream
>> we'll do a relatively expensive call creating a Date and doing timezone
>> conversion.
>>
>> Some gains from loading fewer classes during VM startup, as well.
>>
>> Thanks!
>>
>> /Claes
>