RFR: 8276764: Enable deterministic file content ordering for Jar and Jmod

[Magnus Ihse Bursie]

On Thu, 18 Nov 2021 09:10:16 GMT, Andrew Leonard <aleonard at openjdk.org> wrote:

>> src/jdk.jartool/share/classes/sun/tools/jar/Main.java line 131:
>> 
>>> 129:     // There's also a files array per version
>>> 130:     // Use a LinkedHashMap to keep original insertion ordering
>>> 131:     Map<Integer,String[]> filesMap = new LinkedHashMap<>();
>> 
>> The entries of `filesMap` is sorted by the version.   Is the value of each entry already sorted?  Does that matter?   It's unclear to me since `expand` is called for each entry's value:
>> 
>> 
>>     private void expand() throws IOException {
>>         for (int version : filesMap.keySet()) {
>>             String[] files = filesMap.get(version);
>>             expand(null, files, pathsMap.get(version), version);
>>         }
>>     }
>
> @mlchung the way I looked at this was the filesMap is a HashMap, so the filesMap.keySet() iteration order is not defined (or necessarily deterministic), the expanded order of the file sets for each version could be ver1, ver2, ver3 or ver3, ver2, ver1... the next time you run it with the same parameters.
> LinkedHashMap will ensure the iterated order is as inserted (or as specified in the jar args list..)
> 
> Although you say "filesMap is sorted by version", I don't see where that is done?

I'm guessing Mandy asks not if the keys are sorted -- this is changed by your patch, but if the value retrieved -- the String[], is sorted. It's a valid question, I think. It's not apparent to me at least that this is the case. If it is not sorted when it is inserted it needs to be sorted when extracted.

-------------

PR: https://git.openjdk.java.net/jdk/pull/6395