RFR: 8270317: Large Allocation in CipherSuite [v2]

[Clive Verghese]

On Fri, 16 Jul 2021 04:29:51 GMT, Michael Bien <github.com+114367+mbien at openjdk.org> wrote:

>> src/java.base/share/classes/sun/security/ssl/CipherSuite.java line 865:
>> 
>>> 863:             maps_name.put(cs.name, cs);
>>> 864:             for (String alias : cs.aliases) {
>>> 865:                 maps_name.put(alias, cs);
>> 
>> A minor concern here. HashMap can't have duplicate keys.  what if there are duplicated names/aliases?
>> 
>> Even it's not the case now, CipherSuite is subject to change in the future and I think it is a good opportunity to detect key duplication here. Currently,  it's silently overwritten. This may introduce inconsistent behavior for nameOf.
>
> this could be potentially stored in immutable collections which might be slightly more compact + they throw when they encounter duplicate keys
> 1) change base type to Map
> 2) copy ciphers array into Map.Entry array
> 3) maps_id = Map.ofEntries(entries) // + handle IAE
> 
> similar for the name map but with a list in between.
> 
> there might be a JDK internal shortcut to get to new ImmutableCollections.MapN<>(flatArray) right away without the Map.Entry step - I am sure a reviewer will chime in if there is.

Thank you for the feedback. I have updated to use ImmutableMap. However, I had to use `copyOf(Map)` method instead. 

It would not check for duplicate values. Would it make more sense to add a test case to check for duplicates instead?. If so I can add that, else i'll check for duplicate while creating the map.

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PR: https://git.openjdk.java.net/jdk/pull/4783