RFR: 8320971: Use BufferedInputStream.buf directly when param of implTransferTo() is trusted [v12]

[Markus KARG]

On Tue, 12 Dec 2023 20:18:15 GMT, Sergey Tsypanov <stsypanov at openjdk.org> wrote:

>> It looks like we can skip copying of `byte[]` in `BufferedInputStream.implTransferTo()` for `OutputStreams` residing in `java.io`.
>> 
>> See comment by @vlsi in https://github.com/openjdk/jdk/pull/10525/files#diff-e19c508d1bb6ee78697ecca66947c395adda0d9c49a85bf696e677ecbd977af1R612
>
> Sergey Tsypanov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8320971: Whitespaces

src/java.base/share/classes/com/sun/io/IOStreams.java line 53:

> 51:     public static boolean isTrusted(OutputStream os) {
> 52:         var clazz = os.getClass();
> 53:         return clazz == ByteArrayOutputStream.class

I wonder what the committers think: Do we need a unit test for each trusted class to proof that they actually behave accordingly to the rules of trust listed in the Javadocs?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16879#discussion_r1424981445