RFR: 8328995: launcher can't open jar files where the offset of the manifest is >4GB [v4]

[Liam Miller-Cushon]

On Fri, 29 Mar 2024 18:28:37 GMT, Jiangli Zhou <jiangli at openjdk.org> wrote:

>> Liam Miller-Cushon has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Maximum Zip64 extra field length is 32
>
> src/java.base/share/native/libjli/parse_manifest.c line 506:
> 
>> 504:               jlong offset = 0;
>> 505:               while (offset < cenext) {
>> 506:                 short headerId = ZIPEXT_HDR(base + offset);
> 
> This block of code is very similar to the corresponding part (reading the ZIP64 extension extra fields) in `validate_lochdr`. Perhaps also refractor to a common helper function?

The other loop uses `readAt` to read in additional data and advance through the extra fields, this loop already has access to a buffer that contains all of the data for the extra fields and doesn't need to do that.

I considered having the other loop read in all of the data for the extra fields so there could be a shared helper, but the data is variable length, so that would have required having a large fixed-size buffer or allocating memory, which this code seems to be trying to avoid.

Do you see a good way to share the loop?

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PR Review Comment: https://git.openjdk.org/jdk/pull/18479#discussion_r1544768965