RFR: 8259947: (fs) Optimize UnixPath.encode implementation

[Claes Redestad]

On Tue, 19 Jan 2021 10:46:32 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This patch improves `UnixPath.encode` by reusing `JLA.getBytesNoRepl` (which has fast-paths for common encoding) and avoiding a `toCharArray` call on the input by refactoring the `normalizeNativePath` code to operate on `String`. This might have a cost on files on Mac that need additional native normalization.
>> 
>> This removes another `ThreadLocal` and a source of `SoftReference`s. Together with the UTF-8 fast-path my UTF-8 encoded file system see substantial speed-ups in a trivial `new File(str).toPath()` microbenchmark.
>
> test/micro/org/openjdk/bench/java/io/FileToPath.java line 46:
> 
>> 44:     public String root = "/";
>> 45:     public String trailingSlash = "/test/dir/file/name.txt/";
>> 46:     public String notNormalizedFile = "/test/dir/file//name.txt";
> 
> Can be `private`, I think. As long as those are not `static final`...

Agree this can be cleaned up.

The micro was derived/copied from the `FileOpen` micro in the same package, so comments apply to a pre-existing micro. I'll refactor this to be a subclass inside that micro and clean up both.

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PR: https://git.openjdk.java.net/jdk/pull/2135