8321514: UTF16 string gets constructed incorrectly from codepoints if CompactStrings is not enabled

Co-authored-by: Roger Riggs <rriggs@openjdk.org>
Reviewed-by: rriggs

Author: Aleksei Voitylov

src/java.base/share/classes/java/lang/StringUTF16.java

@@ -415,7 +415,7 @@ public static byte[] toBytes(int[] val, int index, int len) {
         int n = computeCodePointSize(val, index, end);
 
         byte[] buf = newBytesFor(n);
-        return extractCodepoints(val, index, len, buf, 0);
+        return extractCodepoints(val, index, end, buf, 0);
      }
 
     public static byte[] toBytes(char c) {

test/jdk/java/lang/String/Chars.java

@@ -23,8 +23,10 @@
 
 /*
  * @test
- * @bug 8054307 8311906
+ * @bug 8054307 8311906 8321514
  * @summary test String chars() and codePoints()
+ * @run main/othervm -XX:+CompactStrings Chars
+ * @run main/othervm -XX:-CompactStrings Chars
  */
 
 import java.util.Arrays;
@@ -45,6 +47,7 @@ public static void main(String[] args) {
             }
             testChars(cc, ccExp);
             testCharsSubrange(cc, ccExp);
+            testIntsSubrange(ccExp);
             testCPs(cc, cpExp);
 
             // bmp without surrogates
@@ -72,6 +75,7 @@ public static void main(String[] args) {
             cpExp = Arrays.copyOf(cpExp, k);
             testChars(cc, ccExp);
             testCharsSubrange(cc, ccExp);
+            testIntsSubrange(ccExp);
             testCPs(cc, cpExp);
         }
     }
@@ -104,6 +108,27 @@ static void testCharsSubrange(char[] cc, int[] expected) {
         }
     }
 
+    static void testIntsSubrange(int[] expected) {
+        int[] offsets = { 7, 31 };   // offsets to test
+        int LENGTH = 13;
+        for (int i = 0; i < offsets.length; i++) {
+            int offset = Math.max(0, offsets[i]);       // confine to the input array
+            int count = Math.min(LENGTH, expected.length - offset);
+            String str = new String(expected, offset, count);
+            int[] actual = str.chars().toArray();
+            int errOffset = Arrays.mismatch(actual, 0, actual.length,
+                    expected, offset, offset + count);
+            if (errOffset >= 0) {
+                System.err.printf("expected[%d] (%d) != actual[%d] (%d)%n",
+                        offset + errOffset, expected[offset + errOffset],
+                        errOffset, actual[errOffset]);
+                System.err.println("expected: " + Arrays.toString(expected));
+                System.err.println("actual: " + Arrays.toString(actual));
+                throw new RuntimeException("testIntsSubrange failed!");
+            }
+        }
+    }
+
     static void testCPs(char[] cc, int[] expected) {
         String str = new String(cc);
         if (!Arrays.equals(expected, str.codePoints().toArray())) {