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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 *

 * 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,

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package org.openjdk.bench.java.lang;

import org.openjdk.jmh.annotations.Benchmark;

import org.openjdk.jmh.annotations.BenchmarkMode;

import org.openjdk.jmh.annotations.Mode;

import org.openjdk.jmh.annotations.OperationsPerInvocation;

import org.openjdk.jmh.annotations.OutputTimeUnit;

import org.openjdk.jmh.annotations.Scope;

import org.openjdk.jmh.annotations.Setup;

import org.openjdk.jmh.annotations.State;

import java.util.concurrent.TimeUnit;

/**

 * Benchmark measuring System.arraycopy in different ways.

 */

@BenchmarkMode(Mode.AverageTime)

@OutputTimeUnit(TimeUnit.NANOSECONDS)

@State(Scope.Thread)

public class ArrayCopy {

    private static final byte[] TEST_BYTES = "HTTP/1.0".getBytes();

    private static final char[] TEST_CHARS = new char[46];

    private static final Object[] TEST_OBJECTS = new Object[200];  // Uses a minimum of 160 internal positions for internal copying

    // a length which the compiler cannot prove is a constant

    public static int nonConstCharLength = TEST_CHARS.length;

    public static int nonConstByteLength = TEST_BYTES.length;

    public static int nonConstObjectLength = TEST_OBJECTS.length;

    // Use this array to copy objects in.

    public char[] dummyCharArray = new char[TEST_CHARS.length];

    public byte[] dummyByteArray = new byte[TEST_BYTES.length];

    public Object[] dummyObjectArray = new Object[TEST_OBJECTS.length];

    @Setup

    public void setup() {

        for (int i = 0; i < TEST_OBJECTS.length; i++) {

            TEST_OBJECTS[i] = new Object();

            dummyObjectArray[i] = new Object();

        }

    }

    /**

     * This test case do the same work as testArrayCopy. We should make sure

     * testArrayCopy is equally fast or better. Compare the two and you measure

     * the system call versus explicit copy for-loop.

     */

    @Benchmark

    public void copyLoop() {

        for (int j = 0; j < dummyByteArray.length; j++) {

            dummyByteArray[j] = TEST_BYTES[j];

        }

    }

    /**

     * Test that we can optimize away the code since it should not have any side

     * effects

     */

    @Benchmark

    public void copyLoopLocalArray() {

        byte[] localDummyByteArray = new byte[TEST_BYTES.length];

        for (int j = 0; j < localDummyByteArray.length; j++) {

            localDummyByteArray[j] = TEST_BYTES[j];

        }

    }

    /**

     * This test case do the same work as testArrayCopy. We should make sure

     * testArrayCopy is equally fast or better. Compare the two and you measure

     * the system call versus explicit copy for-loop.

     * <p/>

     * Uses non-provable constant length.

     */

    @Benchmark

    public void copyLoopNonConst() {

        for (int i = 0; i < nonConstByteLength; i++) {

            dummyByteArray[i] = TEST_BYTES[i];

        }

    }

    /**

     * This test case do the same work as testCopyLoop. We should make sure

     * testArrayCopy is equally fast or better. Compare the two and you measure

     * the system call versus explicit copy for-loop.

     */

    @Benchmark

    public void arrayCopy() {

        System.arraycopy(TEST_BYTES, 0, dummyByteArray, 0, dummyByteArray.length);

    }

    /**

     * Test that we can optimize away the code since it should not have any side

     * effects

     */

    @Benchmark

    public void arrayCopyLocalArray() {

        byte[] localDummyByteArray = new byte[TEST_BYTES.length];

        System.arraycopy(TEST_BYTES, 0, localDummyByteArray, 0, localDummyByteArray.length);

    }

    /**

     * This test case do the same work as testCopyLoop. We should make sure

     * testArrayCopy is equally fast or better. Compare the two and you measure

     * the system call versus explicit copy for-loop.

     * <p/>

     * Uses non-provable constant length.

     */

    @Benchmark

    public void arrayCopyNonConst() {

        System.arraycopy(TEST_BYTES, 0, dummyByteArray, 0, nonConstByteLength);

    }

    @Benchmark

    public void arrayCopyChar() {

        System.arraycopy(TEST_CHARS, 0, dummyCharArray, 0, dummyCharArray.length);

    }

    @Benchmark

    public void arrayCopyCharNonConst() {

        System.arraycopy(TEST_CHARS, 0, dummyCharArray, 0, nonConstCharLength);

    }

    @Benchmark

    public void arrayCopyObject() {

        System.arraycopy(TEST_OBJECTS, 0, dummyObjectArray, 0, dummyObjectArray.length);

    }

    @Benchmark

    public void arrayCopyObjectNonConst() {

        System.arraycopy(TEST_OBJECTS, 0, dummyObjectArray, 0, nonConstObjectLength);

    }

    /**

     * This test copies inside a object array, that is same source array as dest

     * array. Copies backwards in the array.

     */

    @Benchmark

    @OperationsPerInvocation(40)

    public void arrayCopyObjectSameArraysBackward() {

        for (int i = 0; i < 40; i++) {

            System.arraycopy(dummyObjectArray, i, dummyObjectArray, i + 40, 80);

        }

    }

    /**

     * This test copies inside a object array, that is same source array as dest

     * array. Copies forward in the array. There is a special version for this

     * in JRockit.

     */

    @Benchmark

    @OperationsPerInvocation(40)

    public void arrayCopyObjectSameArraysForward() {

        for (int i = 0; i < 40; i++) {

            System.arraycopy(dummyObjectArray, i + 40, dummyObjectArray, i, 80);

        }

    }

}