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package org.openjdk.bench.java.lang.foreign;

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.Warmup;

import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.invoke.VarHandle;
import java.util.concurrent.TimeUnit;

@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(value = 3, jvmArgsAppend = "--enable-preview")
public class TestAdaptVarHandles extends JavaLayouts {

    static class IntBox {

        private final int value;

        IntBox(int value) {
            this.value = value;
        }

        int intValue() {
            return value;
        }
    }

    static final int ELEM_SIZE = 1_000_000;

    static final MethodHandle INT_TO_INTBOX;
    static final MethodHandle INTBOX_TO_INT;

    static {
        try {
            INT_TO_INTBOX = MethodHandles.lookup()
                    .findConstructor(IntBox.class, MethodType.methodType(void.class, int.class));
            INTBOX_TO_INT = MethodHandles.lookup()
                    .findVirtual(IntBox.class, "intValue", MethodType.methodType(int.class));
        } catch (Throwable ex) {
            throw new ExceptionInInitializerError(ex);
        }
    }

    static final VarHandle VH_ARR_INT = MethodHandles.arrayElementVarHandle(int[].class);

    static final VarHandle VH_BOX_ARR_INT = MethodHandles.filterValue(VH_ARR_INT, INTBOX_TO_INT, INT_TO_INTBOX);

    static final VarHandle VH_BOX_INT = MethodHandles.filterValue(VH_INT, INTBOX_TO_INT, INT_TO_INTBOX);

    static final MethodHandle MH_INT = VH_ARR_INT.toMethodHandle(VarHandle.AccessMode.GET);

    static final MethodHandle MH_BOX_INT = MethodHandles.filterReturnValue(MH_INT, INT_TO_INTBOX);

    int[] base = new int[ELEM_SIZE];
    MemorySegment segment = MemorySegment.ofArray(base);

    @Setup
    public void setup() {
        for (int i = 0; i < ELEM_SIZE; i++) {
            base[i] = i;
        }
    }

    @Benchmark
    public int vh_loop() throws Throwable {
        int sum = 0;
        for (int i = 0; i < ELEM_SIZE; i++) {
            sum += (int) VH_ARR_INT.get(base, i);
        }
        return sum;
    }

    @Benchmark
    public int vh_box_loop() throws Throwable {
        int sum = 0;
        for (int i = 0; i < ELEM_SIZE; i++) {
            sum += ((IntBox) VH_BOX_ARR_INT.get(base, i)).intValue();
        }
        return sum;
    }

    @Benchmark
    public int mh_loop() throws Throwable {
        int sum = 0;
        for (int i = 0; i < ELEM_SIZE; i++) {
            sum += (int) MH_INT.invokeExact(base, i);
        }
        return sum;
    }

    @Benchmark
    public int mh_box_loop() throws Throwable {
        int sum = 0;
        for (int i = 0; i < ELEM_SIZE; i++) {
            sum += ((IntBox) MH_BOX_INT.invokeExact(base, i)).intValue();
        }
        return sum;
    }

    @Benchmark
    public int segment_loop() throws Throwable {
        int sum = 0;
        for (int i = 0; i < ELEM_SIZE; i++) {
            sum += (int)VH_INT.get(segment, (long)i);
        }
        return sum;
    }

    @Benchmark
    public int segment_box_loop() throws Throwable {
        int sum = 0;
        for (int i = 0; i < ELEM_SIZE; i++) {
            sum += ((IntBox)VH_BOX_INT.get(segment, (long)i)).intValue();
        }
        return sum;
    }
}
