RFR: 8219014: (bf) Add absolute bulk put methods which accept a source Buffer

[Martin Thompson]

On Fri, 30 Oct 2020 20:37:53 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

> Please review this proposed fix. The previous incarnation of this review was most recently in mail threads [1, 2] under the old Hg SCM. The implementation changes proposed here are derived from the final (.02) patch posted in [1]. The corresponding CSR is [3].
> 
> The essence of the change is to move the bulk put buffer core functionality to a new method putBuffer(), modify the existing relative bulk put buffer method to call it, and add a new absolute bulk put buffer method which also calls it. The existing test for bulk put buffer functionality is modified to verify the new API.
> 
> This change builds on the work completed for JDK-5029431 (bulk put and get using an array) and JDK-8245121 (relative bulk put buffer with overlapping regions).
> 
> [1] http://mail.openjdk.java.net/pipermail/nio-dev/2020-June/007340.html
> [2] http://mail.openjdk.java.net/pipermail/nio-dev/2020-July/007344.html
> [3] https://bugs.openjdk.java.net/browse/JDK-8248431

The other method implementations which do a absolute put or get do not modify the position. This makes them more useful in a multi-threaded context as different threads can be updating different ranges of the buffer concurrently. To replace Unsafe we need absolute index methods that do not update position.

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PR: https://git.openjdk.java.net/jdk/pull/969