8011135: (bf) CharBuffer.put(String) is slow because of String.charAt() call for each char

Reviewed-by: alanb, redestad

src/java.base/share/classes/java/nio/Heap-X-Buffer.java.template

@@ -270,6 +270,25 @@ class Heap$Type$Buffer$RW$
 #end[rw]
     }
 
+#if[char]
+
+    public $Type$Buffer put(String src, int start, int end) {
+        int length = end - start;
+        checkBounds(start, length, src.length());
+        if (isReadOnly())
+            throw new ReadOnlyBufferException();
+        int pos = position();
+        int lim = limit();
+        int rem = (pos <= lim) ? lim - pos : 0;
+        if (length > rem)
+            throw new BufferOverflowException();
+        src.getChars(start, end, hb, ix(pos));
+        position(pos + length);
+        return this;
+    }
+
+#end[char]
+
     public $Type$Buffer compact() {
 #if[rw]
         System.arraycopy(hb, ix(position()), hb, ix(0), remaining());

test/micro/org/openjdk/bench/java/nio/CharBuffers.java

@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) 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
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * 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.
+ */
+package org.openjdk.bench.java.nio;
+
+import java.nio.CharBuffer;
+import java.util.Arrays;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Level;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+
+@BenchmarkMode(Mode.AverageTime)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@State(Scope.Thread)
+public class CharBuffers {
+
+    @Param({"2", "256", "16384"})
+    public int numChars;
+
+    public String str;
+    public CharBuffer buf;
+
+    @Setup(Level.Iteration)
+    public void createString() {
+        char[] c = new char[numChars];
+        Arrays.fill(c, 'X');
+        str = String.valueOf(c);
+        buf = CharBuffer.allocate(numChars);
+    }
+
+    @Benchmark
+    public CharBuffer putString() {
+        buf.clear();
+        return buf.put(str);
+    }
+
+}