RFR: 8341964: Add mechanism to disable different parts of TLS cipher suite [v4]

[Artur Barashev]

On Thu, 7 Nov 2024 19:02:53 GMT, Sean Mullan <mullan at openjdk.org> wrote:

>> Artur Barashev has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   - Cache the patterns
>>   - Make matching case-sensitive
>>   - Update java.security documentation
>>   - Refactor the tests
>
> src/java.base/share/classes/sun/security/util/AbstractAlgorithmConstraints.java line 126:
> 
>> 124:             }
>> 125: 
>> 126:             Pattern p = patternCache.get(pattern);
> 
> I think you want to use `putIfAbsent` here, so the operation happens atomically.

Actually if we do `patternCache.putIfAbsent(pattern, Pattern.compile(pattern.replace("*", ".*")))` we'll be computing Pattern on every call regardless if it's already present in cache. Also `putIfAbsent` makes no guarantees of atomicity. Better candidate here seems to be `computeIfAbsent` method, but still it would not be as fast as the current solution because it would add an extra `get` call to the cache interaction. That's how exactly `computeIfAbsent` method works:

`     * <pre> {@code
     * if (map.get(key) == null) {
     *     V newValue = mappingFunction.apply(key);
     *     if (newValue != null)
     *         map.put(key, newValue);
     * }
     * }</pre>
`

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PR Review Comment: https://git.openjdk.org/jdk/pull/21841#discussion_r1833308486