RFR: 8259947: Optimize UnixPath.encode

[Chris Hegarty]

On Tue, 19 Jan 2021 00:35:51 GMT, Claes Redestad <redestad 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.

I think that this looks good ( I had a similar thought when looking through this code recently, for a separate issue ).

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Marked as reviewed by chegar (Reviewer).

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