8361209: (bf) Use CharSequence::getChars for StringCharBuffer bulk get methods

Reviewed-by: rriggs, alanb

src/java.base/share/classes/java/nio/StringCharBuffer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2025, 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
@@ -97,7 +97,13 @@ final class StringCharBuffer                                  // package-private
         return str.charAt(index + offset);
     }
 
-    // ## Override bulk get methods for better performance
+    @Override
+    CharBuffer getArray(int index, char[] dst, int dstOffset, int length) {
+        // Note: the variable "offset" is defined and set in the superclass
+        int srcOffset = offset + index;
+        str.getChars(srcOffset, srcOffset + length, dst, dstOffset);
+        return this;
+    }
 
     public final CharBuffer put(char c) {
         throw new ReadOnlyBufferException();

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

@@ -950,12 +950,15 @@ public abstract sealed class $Type$Buffer
         return get(index, dst, 0, dst.length);
     }
 
-    private $Type$Buffer getArray(int index, $type$[] dst, int offset, int length) {
-        if (
+    //
+    // This method does not perform bounds checking which it expects
+    // will have been done by the caller
+    //
+    $Type$Buffer getArray(int index, $type$[] dst, int offset, int length) {
 #if[char]
-            isAddressable() &&
+        assert isAddressable();
 #end[char]
-            ((long)length << $LG_BYTES_PER_VALUE$) > Bits.JNI_COPY_TO_ARRAY_THRESHOLD) {
+        if (((long)length << $LG_BYTES_PER_VALUE$) > Bits.JNI_COPY_TO_ARRAY_THRESHOLD) {
             long bufAddr = address + ((long)index << $LG_BYTES_PER_VALUE$);
             long dstOffset =
                 ARRAY_BASE_OFFSET + ((long)offset << $LG_BYTES_PER_VALUE$);
@@ -1116,6 +1119,10 @@ public abstract sealed class $Type$Buffer
         return this;
     }
 
+    //
+    // This method does not perform bounds checking which it expects
+    // will have been done by the caller
+    //
     void putBuffer(int pos, $Type$Buffer src, int srcPos, int n) {
 #if[rw]
         Object srcBase = src.base();
@@ -1150,9 +1157,13 @@ public abstract sealed class $Type$Buffer
 #if[char]
         } else { // src.isAddressable() == false
             assert StringCharBuffer.class.isInstance(src);
-            int posMax = pos + n;
-            for (int i = pos, j = srcPos; i < posMax; i++, j++)
-                put(i, src.get(j));
+            if (this.hb != null && src instanceof StringCharBuffer scb) {
+                scb.getArray(srcPos, this.hb, pos, n);
+            } else {
+                int posMax = pos + n;
+                for (int i = pos, j = srcPos; i < posMax; i++, j++)
+                    put(i, src.get(j));
+            }
         }
 #end[char]
 #else[rw]
@@ -1342,6 +1353,10 @@ public abstract sealed class $Type$Buffer
         return put(index, src, 0, src.length);
     }
 
+    //
+    // This method does not perform bounds checking which it expects
+    // will have been done by the caller
+    //
     $Type$Buffer putArray(int index, $type$[] src, int offset, int length) {
 #if[rw]
         if (

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

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 2025, 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.
+ */
+package org.openjdk.bench.java.nio;
+
+import java.nio.CharBuffer;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+/**
+ * Benchmark for bulk get methods of a {@code CharBuffer} created from a
+ * {@code CharSequence}.
+ */
+
+@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
+@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
+@State(Scope.Benchmark)
+@Fork(1)
+public class StringCharBufferBulkTransfer {
+    private static final int LENGTH = 16384;
+
+    char[] buf = new char[LENGTH];
+    CharBuffer cb = CharBuffer.wrap(new String(buf));
+    char[] dst = new char[LENGTH];
+    CharBuffer cbw = CharBuffer.allocate(LENGTH);
+
+    @Benchmark
+    public void absoluteBulkGet() {
+        cb.get(0, dst, 0, dst.length);
+    }
+
+    @Benchmark
+    public void relativeBulkGet() {
+        cb.get(dst, 0, dst.length);
+        cb.position(0);
+    }
+
+    @Benchmark
+    public void getChars() {
+        cb.getChars(0, LENGTH, dst, 0);
+    }
+
+    @Benchmark
+    public void absoluteBulkPut() {
+        cbw.put(0, cb, 0, dst.length);
+    }
+}