8333884: MemorySegment::reinterpret removes read-only property

Reviewed-by: liach, sundar
Backport-of: 6f7f0f1

src/java.base/share/classes/java/lang/foreign/MemorySegment.java

@@ -631,6 +631,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * asSlice(offset, newSize, 1);
      * }
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *
@@ -650,6 +653,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * alignment constraint. The returned segment's address is the address of this
      * segment plus the given offset; its size is specified by the given argument.
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *
@@ -677,6 +683,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * asSlice(offset, layout.byteSize(), layout.byteAlignment());
      * }
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *
@@ -703,6 +712,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * asSlice(offset, byteSize() - offset);
      * }
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *
@@ -719,6 +731,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * Returns a new memory segment that has the same address and scope as this segment,
      * but with the provided size.
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *
@@ -757,6 +772,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * scope, and is accessible from any thread. The size of the segment accepted by the
      * cleanup action is {@link #byteSize()}.
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *
@@ -805,6 +823,9 @@ public sealed interface MemorySegment permits AbstractMemorySegmentImpl {
      * scope, and is accessible from any thread. The size of the segment accepted by the
      * cleanup action is {@code newSize}.
      * <p>
+     * If this segment is {@linkplain MemorySegment#isReadOnly() read-only},
+     * the returned segment is also {@linkplain MemorySegment#isReadOnly() read-only}.
+     * <p>
      * The returned memory segment shares a region of backing memory with this segment.
      * Hence, no memory will be allocated or freed by this method.
      *

src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java

@@ -159,7 +159,7 @@ public MemorySegment reinterpretInternal(Class<?> callerClass, long newSize, Sco
                 () -> cleanup.accept(SegmentFactories.makeNativeSegmentUnchecked(address(), newSize)) :
                 null;
         return SegmentFactories.makeNativeSegmentUnchecked(address(), newSize,
-                (MemorySessionImpl)scope, action);
+                (MemorySessionImpl)scope, readOnly, action);
     }
 
     private AbstractMemorySegmentImpl asSliceNoCheck(long offset, long newSize) {

src/java.base/share/classes/jdk/internal/foreign/SegmentFactories.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2023, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -57,14 +57,18 @@ public class SegmentFactories {
     // associated with MemorySegment::ofAddress.
 
     @ForceInline
-    public static MemorySegment makeNativeSegmentUnchecked(long min, long byteSize, MemorySessionImpl sessionImpl, Runnable action) {
+    public static MemorySegment makeNativeSegmentUnchecked(long min,
+                                                           long byteSize,
+                                                           MemorySessionImpl sessionImpl,
+                                                           boolean readOnly,
+                                                           Runnable action) {
         ensureInitialized();
         if (action == null) {
             sessionImpl.checkValidState();
         } else {
             sessionImpl.addCloseAction(action);
         }
-        return new NativeMemorySegmentImpl(min, byteSize, false, sessionImpl);
+        return new NativeMemorySegmentImpl(min, byteSize, readOnly, sessionImpl);
     }
 
     @ForceInline

test/jdk/java/foreign/TestSegments.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2019, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -43,7 +43,6 @@
 import java.util.function.Supplier;
 
 import static java.lang.foreign.ValueLayout.JAVA_INT;
-import static java.lang.foreign.ValueLayout.JAVA_LONG;
 import static org.testng.Assert.*;
 
 public class TestSegments {
@@ -383,9 +382,14 @@ void testReinterpret() {
             assertEquals(MemorySegment.ofAddress(42).reinterpret(100, Arena.ofAuto(), null).byteSize(), 100);
             // check scope and cleanup
             assertEquals(MemorySegment.ofAddress(42).reinterpret(100, arena, s -> counter.incrementAndGet()).scope(), arena.scope());
-            assertEquals(MemorySegment.ofAddress(42).reinterpret(arena, s -> counter.incrementAndGet()).scope(), arena.scope());
+            assertEquals(MemorySegment.ofAddress(42).reinterpret(arena, _ -> counter.incrementAndGet()).scope(), arena.scope());
+            // check read-only state
+            assertFalse(MemorySegment.ofAddress(42).reinterpret(100).isReadOnly());
+            assertTrue(MemorySegment.ofAddress(42).asReadOnly().reinterpret(100).isReadOnly());
+            assertTrue(MemorySegment.ofAddress(42).asReadOnly().reinterpret(100, Arena.ofAuto(), null).isReadOnly());
+            assertTrue(MemorySegment.ofAddress(42).asReadOnly().reinterpret(arena, _ -> counter.incrementAndGet()).isReadOnly());
         }
-        assertEquals(counter.get(), 2);
+        assertEquals(counter.get(), 3);
     }
 
     @Test