[lworld] RFR: 8281295: Prototype serialization/deserialization using Unsafe. [v7]

[Roger Riggs]

> Specify serialization and deserialization of value objects. Value objects are immutable, Externalizable relies on mutation, Externalizable is not supported for value objects. Revised tests and added tests for graphs of value objects.
> 
> Somewhat similar to Record serialization in that back references to the value object store 'null' until the value object is completely deserialized.
> Similar to regular serialization/deserialization of identity objects.  The serialized form is the same.
> Deserialization is done by reading fields and storing into a Buffered larval object, converted to a value object when all of the fields have been read and stored.
> 
> Externalizable and Value Objects are incompatible, value objects are immutable and Externalizable.readExternal is expected to modify the fields of an allocated object.

Roger Riggs has updated the pull request incrementally with one additional commit since the last revision:

  Correct formatting of interface Externalizable

-------------

Changes:
  - all: https://git.openjdk.org/valhalla/pull/761/files
  - new: https://git.openjdk.org/valhalla/pull/761/files/bf1f3a17..c14c27a5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=761&range=06
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=761&range=05-06

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/valhalla/pull/761.diff
  Fetch: git fetch https://git.openjdk.org/valhalla pull/761/head:pull/761

PR: https://git.openjdk.org/valhalla/pull/761