RFR: 8339874: Avoid duplicate checking of trailing slash in ZipFile.getZipEntry [v4]

[Eirik Bjørsnøs]

> Please review this PR which speeds up `ZipFile.getZipEntry` by removing slash-checking logic which is already taking place during lookup in `ZipFile.Source.getEntryPos`. 
> 
> `ZipFile.Source.getEntryPos` includes logic to match a lookup for "name" against a directory entry "name/" (with a trailing slash). However, only the CEN position is currently returned, so `ZipFile.getZipEntry` needs to re-read the name from the CEN and determine if a trailing slash needs to be appended to the name of the returned `ZipEntry`.
> 
> By letting `ZipFile.Source.getEntryPos` return the resolved name along with the CEN position (in a new record `EntryPos`), `ZipFile.getZipEntry` can now instead use the already resolved name. 
> 
> This results in a nice ~18% speedup in the `ZipFileGetEntry.getEntryHit` micro:
> 
> Baseline:
> 
> 
> Benchmark                    (size)  Mode  Cnt   Score   Error  Units
> ZipFileGetEntry.getEntryHit     512  avgt   15  63.713 ? 2.645  ns/op
> ZipFileGetEntry.getEntryHit    1024  avgt   15  67.405 ? 1.474  ns/op
> 
> 
> PR:
> 
> 
> Benchmark                    (size)  Mode  Cnt   Score   Error  Units
> ZipFileGetEntry.getEntryHit     512  avgt   15  52.027 ? 2.669  ns/op
> ZipFileGetEntry.getEntryHit    1024  avgt   15  55.211 ? 1.169  ns/op
> 
> 
> This purely a cleanup and optimization PR, no functional tests are changed or added.

Eirik Bjørsnøs has updated the pull request incrementally with one additional commit since the last revision:

  Add whitespace per review feedback

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/20939/files
  - new: https://git.openjdk.org/jdk/pull/20939/files/b6de843b..f24b833a

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=20939&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=20939&range=02-03

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/20939.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20939/head:pull/20939

PR: https://git.openjdk.org/jdk/pull/20939