RFR: 8272297: FileInputStream should override transferTo() for better performance

[Brian Burkhalter]

On Thu, 12 Aug 2021 11:30:16 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> Please consider this request to add an override `java.io.FileInputStream.transferTo(OutputStream)` with improved performance if the parameter is a `FileOutputStream`.
>
> src/java.base/share/classes/java/io/FileInputStream.java line 371:
> 
>> 369:                 // not, then use the superclass method to copy those remaining
>> 370:                 if (fci.transferTo(pos, count, fco) == count) {
>> 371:                     return count;
> 
> Are you sure this is right? FileChannel transferTo doesn't modify the source channel's position so I assume the method above will finish with the InputStream at its initial position rather than EOF. How are we on test coverage for this case?

You're right, that is stupid. I don't think it affected the benchmark, but testing likely needs to be revisited.

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PR: https://git.openjdk.java.net/jdk/pull/5097