[foreign-memaccess] RFR: 8240874: Add finer-grained access control for memory segments

[Jorn Vernee]

On Wed, 11 Mar 2020 13:25:54 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

> This patch adds a finer-grained access control for memory segments; instead of the ad-hoc `MemorySegment::asReadOnly`,
> we now support a more complete `MemorySegment::withAccessModes`, where access modes is an int mask.
> Supported access modes are `READ`, `WRITE`, `CLOSE` and `ACQUIRE`, which gives much more freedom to clients when it
> comes to create restricted views (I've added a new section on that in the MemorySegment toplevel javadoc).
> I also did some minor changes, mostly to get rid of confinement restrictions where such restrictions were not needed
> (e.g. `MemorySegment::asSlice`).

test/jdk/java/foreign/TestSegments.java line 244:

> 243:         int nActions = AccessActions.values().length;
> 244:         Object[][] results = new Object[nActions * nActions][];
> 245:         for (int accessModes = 0 ; accessModes < results.length ; accessModes++) {

I think this should be:
Suggestion:

        Object[][] results = new Object[1 << nActions][];
Since the number of combinations is 2^4. Though for 4 access modes 4 * 4 and 1 << 4 are both 16, it becomes a problem
if we add or remove access modes.

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

PR: https://git.openjdk.java.net/panama-foreign/pull/45