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

rev 56460 : 8231717: Improve performance of charset decoding when charset is always compactable

@@ -1,7 +1,7 @@
 /*
- * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2019, 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.  Oracle designates this

@@ -189,10 +189,16 @@
                                       LATIN1);
                 } else {
                     return result.with(StringLatin1.inflate(ba, off, len), UTF16);
                 }
             }
+            // fastpath for always compactable single byte
+            if (COMPACT_STRINGS && cd instanceof ArrayDecoder && ((ArrayDecoder)cd).isAlwaysCompactable()) {
+                byte[] dst = new byte[len];
+                ((ArrayDecoder)cd).decodeToLatin1(ba, off, len, dst);
+                return result.with(dst, LATIN1);
+            }
             int en = scale(len, cd.maxCharsPerByte());
             char[] ca = new char[en];
             if (cd instanceof ArrayDecoder) {
                 int clen = ((ArrayDecoder)cd).decode(ba, off, len, ca);
                 return result.with(ca, 0, clen);

@@ -276,10 +282,17 @@
         // ascii fastpath
         if ((cd instanceof ArrayDecoder) &&
             ((ArrayDecoder)cd).isASCIICompatible() && !hasNegatives(ba, off, len)) {
             return decodeLatin1(ba, off, len);
         }
+        // fastpath for always compactable single byte
+        if (COMPACT_STRINGS && cd instanceof ArrayDecoder && ((ArrayDecoder)cd).isAlwaysCompactable()) {
+            byte[] dst = new byte[len];
+            ((ArrayDecoder)cd).decodeToLatin1(ba, off, len, dst);
+            return new Result().with(dst, LATIN1);
+        }
+
         int en = scale(len, cd.maxCharsPerByte());
         if (len == 0) {
             return new Result().with();
         }
         cd.onMalformedInput(CodingErrorAction.REPLACE)