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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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package org.openjdk.bench.java.lang.foreign;

import java.lang.foreign.*;

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

import java.lang.foreign.MemorySegment.Scope;
import java.lang.invoke.MethodHandle;
import java.util.concurrent.TimeUnit;

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

@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.NANOSECONDS)
@Fork(value = 3, jvmArgs = { "--enable-native-access=ALL-UNNAMED", "-Djava.library.path=micro/native" })
public class StrLenTest extends CLayouts {

    Arena arena = Arena.ofConfined();

    SegmentAllocator segmentAllocator;
    SegmentAllocator arenaAllocator;
    SlicingPool pool;

    @Param({"5", "20", "100", "451"})
    public int size;
    public String str;

    static {
        System.loadLibrary("StrLen");
    }

    static final MethodHandle STRLEN;

    static {
        Linker abi = Linker.nativeLinker();
        STRLEN = abi.downcallHandle(abi.defaultLookup().findOrThrow("strlen"),
                FunctionDescriptor.of(C_INT, C_POINTER));
    }

    @Setup
    public void setup() {
        str = makeString(size);
        arenaAllocator = new RingAllocator(arena, size + 1);
        pool = new SlicingPool(size + 1);
        segmentAllocator = SegmentAllocator.prefixAllocator(arena.allocate(size + 1, 1));
    }

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

    @Benchmark
    public int jni_strlen() throws Throwable {
        return strlen(str);
    }

    @Benchmark
    public int panama_strlen_alloc() throws Throwable {
        try (Arena arena = Arena.ofConfined()) {
            MemorySegment segment = arena.allocateFrom(str);
            return (int)STRLEN.invokeExact(segment);
        }
    }

    @Benchmark
    public int panama_strlen_ring() throws Throwable {
        return (int)STRLEN.invokeExact(arenaAllocator.allocateFrom(str));
    }

    @Benchmark
    public int panama_strlen_pool() throws Throwable {
        try (Arena arena = pool.acquire()) {
            return (int) STRLEN.invokeExact(arena.allocateFrom(str));
        }
    }

    @Benchmark
    public int panama_strlen_prefix() throws Throwable {
        return (int)STRLEN.invokeExact(segmentAllocator.allocateFrom(str));
    }

    @Benchmark
    public int panama_strlen_unsafe() throws Throwable {
        MemorySegment address = makeStringUnsafe(str);
        int res = (int) STRLEN.invokeExact(address);
        freeMemory(address);
        return res;
    }

    static MemorySegment makeStringUnsafe(String s) {
        byte[] bytes = s.getBytes();
        int len = bytes.length;
        MemorySegment address = allocateMemory(len + 1);
        MemorySegment str = address.asSlice(0, len + 1);
        str.copyFrom(MemorySegment.ofArray(bytes));
        str.set(JAVA_BYTE, len, (byte)0);
        return address;
    }

    static native int strlen(String str);

    static String makeString(int size) {
        String lorem = """
                Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et
                 dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip
                 ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu
                 fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt
                 mollit anim id est laborum.
                """;
        while (lorem.length() < size) {
            lorem += lorem;
        }
        return lorem.substring(0, size);
    }

    static class RingAllocator implements SegmentAllocator {
        final MemorySegment segment;
        SegmentAllocator current;
        long rem;

        public RingAllocator(Arena session, int size) {
            this.segment = session.allocate(size, 1);
            reset();
        }

        @Override
        public MemorySegment allocate(long byteSize, long byteAlignment) {
            if (rem < byteSize) {
                reset();
            }
            MemorySegment res = current.allocate(byteSize, byteAlignment);
            long lastOffset = res.address() - segment.address() + res.byteSize();
            rem = segment.byteSize() - lastOffset;
            return res;
        }

        void reset() {
            current = SegmentAllocator.slicingAllocator(segment);
            rem = segment.byteSize();
        }
    }

    static class SlicingPool {
        final MemorySegment pool;
        boolean isAcquired = false;

        public SlicingPool(int size) {
            this.pool = Arena.ofAuto().allocate(size);
        }

        public Arena acquire() {
            if (isAcquired) {
                throw new IllegalStateException("An allocator is already in use");
            }
            isAcquired = true;
            return new SlicingPoolAllocator();
        }

        class SlicingPoolAllocator implements Arena {

            final Arena arena = Arena.ofConfined();
            final SegmentAllocator slicing = SegmentAllocator.slicingAllocator(pool);

            public MemorySegment allocate(long byteSize, long byteAlignment) {
                return slicing.allocate(byteSize, byteAlignment)
                        .reinterpret(arena, null);
            }

            @Override
            public Scope scope() {
                return arena.scope();
            }

            public void close() {
                isAcquired = false;
                arena.close();
            }
        }
    }
}