8283325: US_ASCII decoder relies on String.decodeASCII being exhaustive

Reviewed-by: rriggs, dcubed

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

@@ -1032,6 +1032,12 @@ public final class String
     /* package-private */
     static int decodeASCII(byte[] sa, int sp, char[] da, int dp, int len) {
         int count = StringCoding.countPositives(sa, sp, len);
+        while (count < len) {
+            if (sa[sp + count] < 0) {
+                break;
+            }
+            count++;
+        }
         StringLatin1.inflate(sa, sp, da, dp, count);
         return count;
     }

test/jdk/java/nio/charset/CharsetDecoder/ASCIIDecode.java

@@ -0,0 +1,55 @@
+/*
+ * Copyright (c) 2022, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/* @test
+ * @bug 8283325
+ * @summary Ensure that decoding to ASCII from a stream with a non-ASCII
+ *          character correctly decodes up until the byte in error.
+ */
+
+import java.nio.*;
+import java.nio.charset.*;
+import java.util.Arrays;
+
+public class ASCIIDecode {
+
+    public static void main(String[] args) throws Exception {
+        final Charset ascii = Charset.forName("US-ASCII");
+        final CharsetDecoder decoder = ascii.newDecoder();
+
+        byte[] ba = new byte[] { 0x60, 0x60, 0x60, (byte)0xFF };
+
+        // Repeat enough times to test that interpreter and JIT:ed versions
+        // behave the same (without the patch for 8283325 this fails within
+        // 50 000 iterations on the system used for verification)
+        for (int i = 0; i < 100_000; i++) {
+            ByteBuffer bb = ByteBuffer.wrap(ba);
+            char[] ca = new char[4];
+            CharBuffer cb = CharBuffer.wrap(ca);
+            CoderResult buf = decoder.decode(bb, cb, true);
+            if (ca[0] != 0x60 || ca[1] != 0x60 || ca[2] != 0x60) {
+                throw new RuntimeException("Unexpected output on iteration " + i);
+            }
+        }
+    }
+}