RFR: 8293499: Provide jmod --compress option [v4]

[Jaikiran Pai]

On Tue, 13 Sep 2022 07:42:33 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> I have been looking into `make clean-images images` performance, and realized jmod keeps compressing files with default compression level. Tuning that toward lighter compression levels improves build performance considerably, without a heavy loss in *.jmod sizes. 
>> 
>> This PR allows JMOD to select the compression level. Follow-ups would use this in the build system, see #10214.
>> 
>> The interesting asymmetry against `jlink` is: `jlink` provides `--compress` option that only takes `2` for "ZIP compression". (Separately, we could argue if it would be beneficial to extend `--compress` to `jlink` as well, so to select the compression level there too.)
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   More review comments

src/jdk.jlink/share/classes/jdk/tools/jmod/JmodOutputStream.java line 66:

> 64:     private final ZipOutputStream zos;
> 65:     private final LocalDateTime date;
> 66:     private JmodOutputStream(OutputStream out, LocalDateTime date, int compLevel) {

Nit - I think this should be `compressLevel` just like the param name to the static method.

src/jdk.jlink/share/classes/jdk/tools/jmod/JmodTask.java line 1196:

> 1194:             }
> 1195:             try {
> 1196:                 int level = Integer.parseInt(value.substring(idx + 1));

If I'm reading this code correctly, then this call to `substring` can potentially end in a `IndexOutOfBoundsException` if the value is `zip-`. Perhaps add a check above to verify that `idx != value.length()`?

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PR: https://git.openjdk.org/jdk/pull/10213