Summary

Provide a Record mapper for MemorySegments/MemoryLayout pairs whereby given MemorySegment instances can be projected onto new Record instances.

Problem

There is a need to view MemorySegments using MemoryLayouts in a more structured way. Currently, a MemorySegment is just a bag of bytes. Initially, it was thought a view should be a String representation but we arrived at a better solution with a more general mapping capability.

Solution

Given a GroupLayout, the elements in the group are matched with RecordComponents. This can be done for arbitrary element types of arbitrary depth. As a simple example, one can extract a Point like so:

    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]

Specification

A proposed API is documented here: https://cr.openjdk.org/~pminborg/panama/21/v3/javadoc/api/java.base/java/lang/foreign/GroupLayout.html#recordMapper(java.lang.Class)