From 8dc2d9280e9d100374a6e33b5d32905bc909a52d Mon Sep 17 00:00:00 2001
From: Per Minborg <pminborg@openjdk.org>
Date: Fri, 15 Sep 2023 05:43:57 +0000
Subject: [PATCH] 8316190: Improve MemorySegment::toString

Reviewed-by: rriggs
---
 .../foreign/AbstractMemorySegmentImpl.java      |  6 +++++-
 .../classes/jdk/internal/foreign/Utils.java     |  5 +++++
 test/jdk/java/foreign/TestSegments.java         | 17 ++++++++++++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java b/src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
index fc56785ce07..c2c3ef3da18 100644
--- a/src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
+++ b/src/java.base/share/classes/jdk/internal/foreign/AbstractMemorySegmentImpl.java
@@ -505,7 +505,11 @@ public abstract sealed class AbstractMemorySegmentImpl
 
     @Override
     public String toString() {
-        return "MemorySegment{ heapBase: " + heapBase() + " address: 0x" + Long.toHexString(address()) + " byteSize: " + length + " }";
+        return "MemorySegment{ " +
+                heapBase().map(hb -> "heapBase: " + hb + ", ").orElse("") +
+                "address: " + Utils.toHexString(address()) +
+                ", byteSize: " + length +
+                " }";
     }
 
     @Override
diff --git a/src/java.base/share/classes/jdk/internal/foreign/Utils.java b/src/java.base/share/classes/jdk/internal/foreign/Utils.java
index ca1a6941530..3e8f012891e 100644
--- a/src/java.base/share/classes/jdk/internal/foreign/Utils.java
+++ b/src/java.base/share/classes/jdk/internal/foreign/Utils.java
@@ -273,4 +273,9 @@ public final class Utils {
     public static boolean containsNullChars(String s) {
         return s.indexOf('\u0000') >= 0;
     }
+
+    public static String toHexString(long value) {
+        return "0x" + Long.toHexString(value);
+    }
+
 }
diff --git a/test/jdk/java/foreign/TestSegments.java b/test/jdk/java/foreign/TestSegments.java
index b2cd0d5557a..f8f5a2b0896 100644
--- a/test/jdk/java/foreign/TestSegments.java
+++ b/test/jdk/java/foreign/TestSegments.java
@@ -225,6 +225,21 @@ public class TestSegments {
         assertTrue(segment.isAccessibleBy(new Thread()) != isConfined);
     }
 
+    @Test(dataProvider = "segmentFactories")
+    public void testToString(Supplier<MemorySegment> segmentSupplier) {
+        var segment = segmentSupplier.get();
+        String s = segment.toString();
+        assertTrue(s.startsWith("MemorySegment{"));
+        assertTrue(s.contains("address: 0x"));
+        assertTrue(s.contains("byteSize: "));
+        if (segment.heapBase().isPresent()) {
+            assertTrue(s.contains("heapBase: ["));
+        } else {
+            assertFalse(s.contains("heapBase: "));
+        }
+        assertFalse(s.contains("Optional"));
+    }
+
     @DataProvider(name = "segmentFactories")
     public Object[][] segmentFactories() {
         List<Supplier<MemorySegment>> l = List.of(
@@ -233,7 +248,7 @@ public class TestSegments {
                 () -> MemorySegment.ofArray(new double[] { 1d, 2d, 3d, 4d} ),
                 () -> MemorySegment.ofArray(new float[] { 1.0f, 2.0f, 3.0f, 4.0f }),
                 () -> MemorySegment.ofArray(new int[] { 1, 2, 3, 4 }),
-                () -> MemorySegment.ofArray(new long[] { 1l, 2l, 3l, 4l } ),
+                () -> MemorySegment.ofArray(new long[] { 1L, 2L, 3L, 4L } ),
                 () -> MemorySegment.ofArray(new short[] { 1, 2, 3, 4 } ),
                 () -> Arena.ofAuto().allocate(4L, 1),
                 () -> Arena.ofAuto().allocate(4L, 8),