[foreign-memaccess+abi] RFR: 8291639: Improve the ability to visualize a MemorySegment in human readable forms [v2]
Glavo
duke at openjdk.org
Fri May 26 14:49:17 UTC 2023
On Fri, 26 May 2023 13:06:57 GMT, Per Minborg <pminborg at openjdk.org> wrote:
>> This PR proposes to add a "Record Mapper" that allows `MemorySegment` instances to be projected onto `Record` types given `GroupLayout` instances.
>>
>> Here is a simple example of how to use the mapper:
>>
>>
>> private static final GroupLayout POINT_LAYOUT = MemoryLayout.structLayout(
>> JAVA_INT.withName("x"),
>> JAVA_INT.withName("y"));
>>
>> MemorySegment segment = MemorySegment.ofArray(new int[]{3, 4});
>>
>> Point point = POINT_LAYOUT.recordMapper(Point.class)
>> .apply(segment); // Point[x=3, y=4]
>>
>>
>> I think the implementation can be improved later, for example by de-duplicating handling of arrays and maybe add recursive "un-pealing" of multidimensional arrays.
>
> Per Minborg has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 29 commits:
>
> - Merge master
> - Fix typos
> - Clean up toString methods
> - Add support for MemoryAddress arrays and improve docs
> - Improve javadoc
> - Change to IAE if mapper fails
> - Remove caching
> - Add tests for initial issue examples
> - Clean up and optimize
> - Add support for multidimensional records
> - ... and 19 more: https://git.openjdk.org/panama-foreign/compare/bee4503b...1d7db589
Is it possible that we will get something like this in the future:
C Header:
struct Point {
int x, y;
};
extern void f1(struct Point p);
extern void f2(struct Point *pp);
Java Code:
record Point(int x, int y) {}
GroupLayout pointLayout = MemoryLayout.structLayout(
JAVA_INT.withName("x"),
JAVA_INT.withName("y"));
ValueLayout pointValueLayout = pointLayout.withJavaType(Point.class);
ValueLayout pointPtrLayout = ADDRESS.withTargetLayout(pointLayout).withJavaType(Point.class);
MethodHandle f1 = nativeLinker.downcallHandle(lookup.find("f1").get(), FunctionDescriptor.ofVoid(pointValueLayout));
MethodHandle f2 = nativeLinker.downcallHandle(lookup.find("f2").get(), FunctionDescriptor.ofVoid(pointPtrLayout));
f1.invoke(new Point(10, 20)); // ok
f2.invoke(new Point(10, 20)); // ok
-------------
PR Comment: https://git.openjdk.org/panama-foreign/pull/833#issuecomment-1564505674
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