Adds a new `ofFileChannel(FileChannel channel, long offset, long length)`
method to `java.net.HttpRequest.BodyPublishers` to provide an `HttpClient`
publisher to upload a certain region of a file. The new publisher does not
modify the state of the passed `FileChannel`, streams the file channel bytes as
it publishes (i.e., avoids reading the entire file into the memory), and can be
leveraged to implement sliced uploads. As noted in the Javadoc:
> The file channel will not be closed upon completion. The caller is
> expected to manage the life cycle of the channel, and close it
> appropriately when not needed anymore.
### Implementation notes
- `FileChannel` is preferred over `{Readable,Seekable}ByteChannel`, since the
latter does not provide a positional read without modifying the state of the
`FileChannel`, which is necessary to use a single `FileChannel` instance to
implement sliced uploads.
- `ofFileChannel(FileChannel,long,long)` is preferred over
`ofPath(Path,long,long)` to avoid overloading the maximum file descriptor limit
of the platform.
-------------
Commit messages:
- Add `HttpRequest.BodyPublishers::ofFileChannel` along with tests
Changes: https://git.openjdk.org/jdk/pull/26155/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26155&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8329829
Stats: 836 lines in 4 files changed: 831 ins; 2 del; 3 mod
Patch: https://git.openjdk.org/jdk/pull/26155.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/26155/head:pull/26155
PR: https://git.openjdk.org/jdk/pull/26155
