4833719: (bf) Views of MappedByteBuffers are not MappedByteBuffers, and cannot be forced

[bplb]

Please consider this proposal to add covariant overrides to MappedByteBuffer for the methods compact(), duplicate(), slice(), and slice(int,int).

The methods in question are added as abstract specifications in MappedByteBuffer and their implementations in Direct-X-Buffer.java.template. In MappedByteBuffer the isSync() method is changed to have package access, and a final package scope method FileDescriptor fileDescriptor() is added to return the associated file descriptor. Specification verbiage is added to the new covariant overrides, and the specification of force() is enhanced slightly. (The unmapper() method offers an alternative way to obtain the file descriptor and sync mode without the need for package access fileDescriptor() and isSync() methods.)

In Direct-X-Buffer.java.template the constructor for duplicates and slices is modified to accept parameters for the file descriptor and sync mode for byte buffers. The uses of this constructor are correspondingly modified.

A test is added to exercise the new methods. Verifying that force() is actually doing anything is not verified by this test but was checked manually. The change passes all other existing tests in tiers 1-3.

Other methods for which it might be worth adding covariant overrides are the get() and put() methods which return a buffer, and, less interesting, the put$Type$() methods.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-4833719: (bf) Views of MappedByteBuffers are not MappedByteBuffers, and cannot be forced

Reviewers

• Andrew Dinn (@adinn - Reviewer) ⚠️ Review applies to dec7dc9

Download

To checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/2902/head:pull/2902
$ git checkout pull/2902

To update a local copy of the PR:
$ git checkout pull/2902
$ git pull https://git.openjdk.java.net/jdk pull/2902/head

[bridgekeeper]

👋 Welcome back bpb! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@bplb The following label will be automatically applied to this pull request:

• nio

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[bplb]

/csr

[openjdk]

@bplb has indicated that a compatibility and specification (CSR) request is needed for this pull request.
@bplb please create a CSR request and add link to it in JDK-4833719. This pull request cannot be integrated until the CSR request is approved.

[mlbridge]

Webrevs

• 05: Full - Incremental (3127ee0)
• 04: Full - Incremental (1e2eac0)
• 03: Full - Incremental (6bd09bf)
• 02: Full - Incremental (dfe6364)
• 01: Full - Incremental (eaeee3c)
• 00: Full (dec7dc9)

[adinn]

This looks good.

[bplb]

CSR filed: https://bugs.openjdk.java.net/browse/JDK-8263620.

[bplb]

Once the CSR is reviewed and appoved then this PR will be ready to integrate.

[openjdk]

@bplb This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

4833719: (bf) Views of MappedByteBuffers are not MappedByteBuffers, and cannot be forced

Reviewed-by: adinn

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 105 new commits pushed to the master branch:

• 0ff8168: 8258957: DocLint: check for HTML start element at end of body
• 3d7f912: 8220266: add support for additional metadata in add/remove programs
• 37f494c: 8260619: Add final modifier to several DataFlavor static fields
• cfc9aa3: 8264002: Delete outdated assumptions about ColorSpace initialization
• 623f0b6: 8262235: Remove unnecessary logic in hugetlbfs_sanity_check()
• 1a13c9e: 8263473: Update annotation terminology (2)
• 3e751a5: 8263198: javadoc HELP page
• 5ca5962: 8259926: Error in jpackage sample usage in the help text
• 70d3401: 8263887: Re-create default icons
• 133a63b: 8263968: CDS: java/lang/ModuleLayer.EMPTY_LAYER should be singleton
• ... and 95 more: https://git.openjdk.java.net/jdk/compare/6aa28b3bdb78eb041a963d659d61e1622bc43ef8...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[bplb]

/integrate

[openjdk]

@bplb Since your change was applied there have been 118 commits pushed to the master branch:

• 8307aa6: 8264165: jpackage BasicTest fails after JDK-8220266: Check help text contains plaform specific parameters
• c037e1e: 8263454: com.apple.laf.AquaFileChooserUI ignores the result of String.trim()
• a1e717f: 8264146: Make Mutex point to rather than embed _name
• f69afba: 8263300: add HtmlId for the block containing a class's description.
• d82464f: 8263528: Make static page ids safe from collision with language elements
• d602ae0: 8263884: Clean up os::is_allocatable() across Posix platforms
• a9d287a: 8260388: Listing (sub)packages at package level of API documentation
• 8120064: 8263781: C2: Cannot hoist independent load above arraycopy
• 9689863: 8262295: C2: Out-of-Bounds Array Load from Clone Source
• a678a38: 8263743: redundant lock in SSLSocketImpl
• ... and 108 more: https://git.openjdk.java.net/jdk/compare/6aa28b3bdb78eb041a963d659d61e1622bc43ef8...master

Your commit was automatically rebased without conflicts.

Pushed as commit b006f22.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.