RFR: 8299576: Reimplement java.io.Bits using VarHandle access [v2]

[Per Minborg]

On Wed, 4 Jan 2023 10:49:18 GMT, Per Minborg <pminborg at openjdk.org> wrote:

>> Do we need this test at all, because this code is tested to extense through RandomAccessFile? We had no test before, so why add a new one here?
>> 
>> Otherwise: PR looks good.
>
>> Do we need this test at all, because this code is tested to extense through RandomAccessFile? We had no test before, so why add a new one here?
>> 
>> Otherwise: PR looks good.
> 
> There are overlaps of the RAF and Bits tests but the latter tests additional aspects such as unaligned access and edge cases with exceptions. So, I think we should keep the proposed tests.

> @minborg Amazing piece!
> 
> Will `java.lang.invoke.VarHandle` instances be shared in JDK to reuse in other places?
> 
> The [jsoniter-scala-coreJVM](https://github.com/plokhotnyuk/jsoniter-scala/tree/master/jsoniter-scala-core/jvm/src/main/scala/com/github/plokhotnyuk/jsoniter_scala/core) module of the [jsoniter-scala](https://github.com/plokhotnyuk/jsoniter-scala) project has a lot of SWAR tricks that use `java.lang.invoke.VarHandle` to speed up parsing/serialization of primitives, `java.math.BigDecimal`, and `java.time.*` classes from/to textual representation.
> 
> Are you interested to port some of them to JDK as it was done for `java.util.UUID` parsing [here](https://github.com/openjdk/jdk/commit/ebadfaeb2e1cc7b5ce5f101cd8a539bc5478cf5b)?

Thanks. I think instances will be private to this class and other have to be created elsewhere if needed. 

Do you see any concrete examples of classes in the JDK that could benefit from a "VarHandlization"?

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PR: https://git.openjdk.org/jdk/pull/11840