8294432: Add provisions to calculate hash values from MemorySegments

Reviewed-by: mcimadamore

src/java.base/share/classes/jdk/internal/foreign/SegmentBulkOperations.java

@@ -28,7 +28,9 @@ package jdk.internal.foreign;
 import jdk.internal.misc.ScopedMemoryAccess;
 import jdk.internal.util.Architecture;
 import jdk.internal.util.ArraysSupport;
+import jdk.internal.util.ByteArrayLittleEndian;
 import jdk.internal.vm.annotation.ForceInline;
+import jdk.internal.vm.annotation.Stable;
 
 import java.lang.foreign.MemorySegment;
 
@@ -156,6 +158,94 @@ public final class SegmentBulkOperations {
         }
     }
 
+    private static final @Stable int[] POWERS_OF_31 = new int[]{
+            0x0000001f, 0x000003c1, 0x0000745f, 0x000e1781,
+            0x01b4d89f, 0x34e63b41, 0x67e12cdf, 0x94446f01};
+
+    /**
+     * {@return a 32-bit hash value calculated from the content in the provided
+     *          {@code segment} between the provided offsets}
+     * <p>
+     * The method is implemented as a 32-bit polynomial hash function equivalent to:
+     * {@snippet lang=java :
+     *     final long length = toOffset - fromOffset;
+     *     segment.checkBounds(fromOffset, length);
+     *     int result = 1;
+     *     for (long i = fromOffset; i < toOffset; i++) {
+     *         result = 31 * result + segment.get(JAVA_BYTE, i);
+     *     }
+     *     return result;
+     * }
+     * but is potentially more performant.
+     *
+     * @param segment    from which a content hash should be computed
+     * @param fromOffset starting offset (inclusive) in the segment
+     * @param toOffset   ending offset (non-inclusive) in the segment
+     * @throws WrongThreadException if this method is called from a thread {@code T},
+     *         such that {@code srcSegment.isAccessibleBy(T) == false}
+     * @throws IllegalStateException if the {@linkplain MemorySegment#scope() scope}
+     *         associated with {@code segment} is not
+     *         {@linkplain MemorySegment.Scope#isAlive() alive}
+     * @throws IndexOutOfBoundsException if either {@code fromOffset} or {@code toOffset}
+     *                                   are {@code > segment.byteSize}
+     * @throws IndexOutOfBoundsException if either {@code fromOffset} or {@code toOffset}
+     *                                   are {@code < 0}
+     * @throws IndexOutOfBoundsException if {@code toOffset - fromOffset} is {@code < 0}
+     */
+    @ForceInline
+    public static int contentHash(AbstractMemorySegmentImpl segment, long fromOffset, long toOffset) {
+        final long length = toOffset - fromOffset;
+        segment.checkBounds(fromOffset, length);
+        if (length == 0) {
+            // The state has to be checked explicitly for zero-length segments
+            segment.scope.checkValidState();
+            return 1;
+        }
+        int result = 1;
+        final long longBytes = length & ((1L << 62) - 8);
+        final long limit = fromOffset + longBytes;
+        for (; fromOffset < limit; fromOffset += 8) {
+            long val = SCOPED_MEMORY_ACCESS.getLongUnaligned(segment.sessionImpl(), segment.unsafeGetBase(), segment.unsafeGetOffset() + fromOffset, !Architecture.isLittleEndian());
+            result = result * POWERS_OF_31[7]
+                    + ((byte) (val >>> 56)) * POWERS_OF_31[6]
+                    + ((byte) (val >>> 48)) * POWERS_OF_31[5]
+                    + ((byte) (val >>> 40)) * POWERS_OF_31[4]
+                    + ((byte) (val >>> 32)) * POWERS_OF_31[3]
+                    + ((byte) (val >>> 24)) * POWERS_OF_31[2]
+                    + ((byte) (val >>> 16)) * POWERS_OF_31[1]
+                    + ((byte) (val >>> 8)) * POWERS_OF_31[0]
+                    + ((byte) val);
+        }
+        int remaining = (int) (length - longBytes);
+        // 0...0X00
+        if (remaining >= 4) {
+            int val = SCOPED_MEMORY_ACCESS.getIntUnaligned(segment.sessionImpl(), segment.unsafeGetBase(), segment.unsafeGetOffset() + fromOffset, !Architecture.isLittleEndian());
+            result = result * POWERS_OF_31[3]
+                    + ((byte) (val >>> 24)) * POWERS_OF_31[2]
+                    + ((byte) (val >>> 16)) * POWERS_OF_31[1]
+                    + ((byte) (val >>> 8)) * POWERS_OF_31[0]
+                    + ((byte) val);
+            fromOffset += 4;
+            remaining -= 4;
+        }
+        // 0...00X0
+        if (remaining >= 2) {
+            short val = SCOPED_MEMORY_ACCESS.getShortUnaligned(segment.sessionImpl(), segment.unsafeGetBase(), segment.unsafeGetOffset() + fromOffset, !Architecture.isLittleEndian());
+            result = result * POWERS_OF_31[1]
+                    + ((byte) (val >>> 8)) * POWERS_OF_31[0]
+                    + ((byte) val);
+            fromOffset += 2;
+            remaining -= 2;
+        }
+        // 0...000X
+        if (remaining == 1) {
+            byte val = SCOPED_MEMORY_ACCESS.getByte(segment.sessionImpl(), segment.unsafeGetBase(), segment.unsafeGetOffset() + fromOffset);
+            result = result * POWERS_OF_31[0]
+                    + val;
+        }
+        return result;
+    }
+
     @ForceInline
     public static long mismatch(AbstractMemorySegmentImpl src, long srcFromOffset, long srcToOffset,
                                 AbstractMemorySegmentImpl dst, long dstFromOffset, long dstToOffset) {

test/jdk/java/foreign/TestSegmentBulkOperationsContentHash.java

@@ -0,0 +1,147 @@
+/*
+ * Copyright (c) 2024, 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.
+ */
+
+/*
+ * @test
+ * @summary Test SegmentBulkOperations::contentHash
+ * @modules java.base/jdk.internal.foreign
+ * @run junit TestSegmentBulkOperationsContentHash
+ */
+
+import jdk.internal.foreign.AbstractMemorySegmentImpl;
+import jdk.internal.foreign.SegmentBulkOperations;
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.MemorySegment;
+import java.lang.foreign.ValueLayout;
+import java.util.Arrays;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicReference;
+import java.util.stream.IntStream;
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+final class TestSegmentBulkOperationsContentHash {
+
+    @ParameterizedTest
+    @MethodSource("sizes")
+    @Disabled
+    void testHashValues(int len) {
+        try (var arena = Arena.ofConfined()) {
+            for (int i = Byte.MIN_VALUE; i <= Byte.MAX_VALUE ; i++) {
+                var segment = arena.allocate(len);
+                segment.fill((byte) i);
+                int hash = hash(segment);
+                int expected = Arrays.hashCode(segment.toArray(ValueLayout.JAVA_BYTE));
+                assertEquals(expected, hash, Arrays.toString(segment.toArray(ValueLayout.JAVA_BYTE)));
+            }
+        }
+    }
+
+    @ParameterizedTest
+    @MethodSource("sizes")
+    void testOffsets(int len) {
+        if (len < 2) {
+            return;
+        }
+        try (var arena = Arena.ofConfined()) {
+            for (int i = Byte.MIN_VALUE; i <= Byte.MAX_VALUE ; i++) {
+                var segment = arena.allocate(len);
+                segment.fill((byte) i);
+                int hash = hash(segment, 1, segment.byteSize() - 1);
+                MemorySegment slice = segment.asSlice(1, segment.byteSize() - 2);
+                byte[] arr = slice.toArray(ValueLayout.JAVA_BYTE);
+                System.out.println(Arrays.toString(arr));
+                int expected = Arrays.hashCode(arr);
+                assertEquals(expected, hash, Arrays.toString(segment.toArray(ValueLayout.JAVA_BYTE)));
+            }
+        }
+    }
+
+    @ParameterizedTest
+    @MethodSource("sizes")
+    void testOutOfBounds(int len) {
+        try (var arena = Arena.ofConfined()) {
+            var segment = arena.allocate(len);
+            assertThrows(IndexOutOfBoundsException.class,
+                    () -> hash(segment, 0, segment.byteSize() + 1));
+            assertThrows(IndexOutOfBoundsException.class,
+                    () -> hash(segment, 0, -1));
+            assertThrows(IndexOutOfBoundsException.class,
+                    () -> hash(segment, -1, 0));
+            if (len > 2) {
+                assertThrows(IndexOutOfBoundsException.class,
+                        () -> hash(segment, 2, 1));
+            }
+        }
+    }
+
+    @ParameterizedTest
+    @MethodSource("sizes")
+    void testConfinement(int len) {
+        try (var arena = Arena.ofConfined()) {
+            var segment = arena.allocate(len);
+            AtomicReference<RuntimeException> ex = new AtomicReference<>();
+            CompletableFuture<Void> future = CompletableFuture.runAsync(() -> {
+                try {
+                    hash(segment);
+                } catch (RuntimeException e) {
+                    ex.set(e);
+                }
+            });
+            future.join();
+            assertInstanceOf(WrongThreadException.class, ex.get());
+        }
+    }
+
+    @ParameterizedTest
+    @MethodSource("sizes")
+    void testScope(int len) {
+        var arena = Arena.ofConfined();
+        var segment = arena.allocate(len);
+        arena.close();
+        assertThrows(IllegalStateException.class, () -> hash(segment));
+    }
+
+    private static int hash(MemorySegment segment) {
+        return hash(segment, 0, segment.byteSize());
+    }
+
+    private static int hash(MemorySegment segment, long fromOffset, long toOffset) {
+        return SegmentBulkOperations.contentHash((AbstractMemorySegmentImpl) segment, fromOffset, toOffset);
+    }
+
+    private static final int MAX_SIZE = 1 << 10;
+
+    private static Stream<Arguments> sizes() {
+        return IntStream.of(0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 23, 32, 63, 128, 256, 511, MAX_SIZE)
+                .boxed()
+                .map(Arguments::of);
+    }
+
+}

test/micro/org/openjdk/bench/java/lang/foreign/SegmentBulkHash.java

@@ -0,0 +1,101 @@
+/*
+ *  Copyright (c) 2024, 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.lang.foreign;
+
+import jdk.internal.foreign.AbstractMemorySegmentImpl;
+import jdk.internal.foreign.SegmentBulkOperations;
+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.Param;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.Warmup;
+
+import java.lang.foreign.Arena;
+import java.lang.foreign.MemorySegment;
+import java.util.Arrays;
+import java.util.Random;
+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(Scope.Thread)
+@OutputTimeUnit(TimeUnit.NANOSECONDS)
+@Fork(value = 3, jvmArgs = {"--add-exports=java.base/jdk.internal.foreign=ALL-UNNAMED"})
+public class SegmentBulkHash {
+
+    @Param({"8", "64"})
+    public int ELEM_SIZE;
+
+    byte[] array;
+    AbstractMemorySegmentImpl heapSegment;
+    AbstractMemorySegmentImpl nativeSegment;
+
+    @Setup
+    public void setup() {
+        // Always use the same alignment regardless of size
+        nativeSegment = (AbstractMemorySegmentImpl) Arena.ofAuto().allocate(ELEM_SIZE, 16);
+        var rnd = new Random(42);
+        for (int i = 0; i < ELEM_SIZE; i++) {
+            nativeSegment.set(JAVA_BYTE, i, (byte) rnd.nextInt(Byte.MIN_VALUE, Byte.MAX_VALUE));
+        }
+        array = nativeSegment.toArray(JAVA_BYTE);
+        heapSegment = (AbstractMemorySegmentImpl) MemorySegment.ofArray(array);
+    }
+
+    @Benchmark
+    public int array() {
+        return Arrays.hashCode(array);
+    }
+
+    @Benchmark
+    public int heapSegment() {
+        return SegmentBulkOperations.contentHash(heapSegment, 0, ELEM_SIZE);
+    }
+
+    @Benchmark
+    public int nativeSegment() {
+        return SegmentBulkOperations.contentHash(nativeSegment, 0, ELEM_SIZE);
+    }
+
+    @Benchmark
+    public int nativeSegmentJava() {
+        int result = 1;
+        for (long i = 0; i < ELEM_SIZE; i++) {
+            result = 31 * result + nativeSegment.get(JAVA_BYTE, i);
+        }
+        return result;
+    }
+
+}
+