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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 *
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 * 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.
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package org.openjdk.bench.java.lang.foreign;

import java.lang.foreign.Arena;
import java.lang.foreign.MemorySegment;

import org.openjdk.jmh.annotations.Benchmark;
import org.openjdk.jmh.annotations.BenchmarkMode;
import org.openjdk.jmh.annotations.Fork;
import org.openjdk.jmh.annotations.Measurement;
import org.openjdk.jmh.annotations.Mode;
import org.openjdk.jmh.annotations.OutputTimeUnit;
import org.openjdk.jmh.annotations.Setup;
import org.openjdk.jmh.annotations.State;
import org.openjdk.jmh.annotations.TearDown;
import org.openjdk.jmh.annotations.Warmup;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;
import java.util.Iterator;
import java.util.concurrent.TimeUnit;

import static java.lang.foreign.ValueLayout.JAVA_INT;

@BenchmarkMode(Mode.AverageTime)
@Warmup(iterations = 5, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@Measurement(iterations = 10, time = 500, timeUnit = TimeUnit.MILLISECONDS)
@State(org.openjdk.jmh.annotations.Scope.Thread)
@OutputTimeUnit(TimeUnit.MILLISECONDS)
@Fork(3)

public class LoopOverSlice {

    static final int ELEM_SIZE = 1_000_000;
    static final int CARRIER_SIZE = (int)JAVA_INT.byteSize();
    static final int ALLOC_SIZE = ELEM_SIZE * CARRIER_SIZE;

    Arena arena;
    MemorySegment nativeSegment, heapSegment;
    IntBuffer nativeBuffer, heapBuffer;

    @Setup
    public void setup() {
        arena = Arena.ofConfined();
        nativeSegment = arena.allocate(ALLOC_SIZE, 1);
        heapSegment = MemorySegment.ofArray(new int[ELEM_SIZE]);
        nativeBuffer = ByteBuffer.allocateDirect(ALLOC_SIZE).order(ByteOrder.LITTLE_ENDIAN).asIntBuffer();
        heapBuffer = IntBuffer.wrap(new int[ELEM_SIZE]);
    }

    @TearDown
    public void tearDown() {
        arena.close();
    }

    @Benchmark
    public void native_segment_slice_loop() {
        new NativeSegmentWrapper(nativeSegment).forEach(NativeSegmentWrapper.Element::get);
    }

    @Benchmark
    public void native_buffer_slice_loop() {
        new NativeBufferWrapper(nativeBuffer).forEach(NativeBufferWrapper.Element::get);
    }

    @Benchmark
    public void heap_segment_slice_loop() {
        new HeapSegmentWrapper(heapSegment).forEach(HeapSegmentWrapper.Element::get);
    }

    @Benchmark
    public void heap_buffer_slice_loop() {
        new HeapBufferWrapper(heapBuffer).forEach(HeapBufferWrapper.Element::get);
    }

    class HeapSegmentWrapper implements Iterable<HeapSegmentWrapper.Element> {
        final MemorySegment segment;

        public HeapSegmentWrapper(MemorySegment segment) {
            this.segment = segment;
        }

        @Override
        public Iterator<Element> iterator() {
            return new Iterator<Element>() {

                MemorySegment current = segment;

                @Override
                public boolean hasNext() {
                    return current.byteSize() > 4;
                }

                @Override
                public Element next() {
                    Element element = new Element(current);
                    current = current.asSlice(4);
                    return element;
                }
            };
        }

        static class Element {
            final MemorySegment segment;

            public Element(MemorySegment segment) {
                this.segment = segment;
            }

            int get() {
                return segment.getAtIndex(JAVA_INT, 0);
            }
        }
    }

    class NativeSegmentWrapper implements Iterable<NativeSegmentWrapper.Element> {
        final MemorySegment segment;

        public NativeSegmentWrapper(MemorySegment segment) {
            this.segment = segment;
        }

        @Override
        public Iterator<Element> iterator() {
            return new Iterator<Element>() {

                MemorySegment current = segment;

                @Override
                public boolean hasNext() {
                    return current.byteSize() > 4;
                }

                @Override
                public Element next() {
                    Element element = new Element(current);
                    current = current.asSlice(4);
                    return element;
                }
            };
        }

        static class Element {
            final MemorySegment segment;

            public Element(MemorySegment segment) {
                this.segment = segment;
            }

            int get() {
                return segment.getAtIndex(JAVA_INT, 0);
            }
        }
    }

    class NativeBufferWrapper implements Iterable<NativeBufferWrapper.Element> {
        final IntBuffer buffer;

        public NativeBufferWrapper(IntBuffer buffer) {
            this.buffer = buffer;
        }

        @Override
        public Iterator<Element> iterator() {
            return new Iterator<Element>() {

                IntBuffer current = buffer;

                @Override
                public boolean hasNext() {
                    return current.position() < current.limit();
                }

                @Override
                public Element next() {
                    Element element = new Element(current);
                    int lim = current.limit();
                    current = current.slice(1, lim - 1);
                    return element;
                }
            };
        }

        static class Element {
            final IntBuffer buffer;

            public Element(IntBuffer segment) {
                this.buffer = segment;
            }

            int get() {
                return buffer.get( 0);
            }
        }
    }

    class HeapBufferWrapper implements Iterable<HeapBufferWrapper.Element> {
        final IntBuffer buffer;

        public HeapBufferWrapper(IntBuffer buffer) {
            this.buffer = buffer;
        }

        @Override
        public Iterator<Element> iterator() {
            return new Iterator<Element>() {

                IntBuffer current = buffer;

                @Override
                public boolean hasNext() {
                    return current.position() < current.limit();
                }

                @Override
                public Element next() {
                    Element element = new Element(current);
                    int lim = current.limit();
                    current = current.slice(1, lim - 1);
                    return element;
                }
            };
        }

        static class Element {
            final IntBuffer buffer;

            public Element(IntBuffer segment) {
                this.buffer = segment;
            }

            int get() {
                return buffer.get( 0);
            }
        }
    }
}