fix: 389: Bytes.hashCode() can be optimized (#391)

Fixes: #389
Reviewed-by: Anthony Petrov <[email protected]>, Ivan Malygin <[email protected]>
Signed-off-by: Artem Ananev <[email protected]>

pbj-core/pbj-runtime/src/jmh/java/com/hedera/pbj/runtime/io/BytesHashCode.java

@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: Apache-2.0
+package com.hedera.pbj.runtime.io;
+
+import com.hedera.pbj.runtime.io.buffer.Bytes;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Random;
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Level;
+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.infra.Blackhole;
+
+@Fork(value = 1)
+@State(Scope.Benchmark)
+public class BytesHashCode {
+
+    private static final Random RANDOM = new Random(98765);
+
+    @Param({"10000"})
+    public int size = 10000;
+
+    private List<Bytes> arrays;
+    private List<Bytes> slices;
+
+    @Setup(Level.Trial)
+    public void init() {
+        if (arrays == null) {
+            arrays = new ArrayList<>(size);
+            slices = new ArrayList<>(size);
+            for (int i = 0; i < size; i++) {
+                final int len = RANDOM.nextInt(99) + 1;
+                final byte[] array = new byte[len];
+                for (int j = 0; j < len; j++) {
+                    array[j] = (byte) RANDOM.nextInt();
+                }
+                final Bytes b = Bytes.wrap(array);
+                arrays.add(b);
+                final int blen = (int) b.length();
+                if (blen < 2) {
+                    slices.add(b);
+                } else {
+                    final int start = RANDOM.nextInt(blen / 2);
+                    final int length = RANDOM.nextInt(blen - start);
+                    slices.add(b.slice(start, length));
+                }
+            }
+        }
+    }
+
+    @Benchmark
+    public void testHashCode(final Blackhole blackhole) {
+        for (final Bytes array : arrays) {
+            blackhole.consume(array.hashCode());
+        }
+    }
+
+    @Benchmark
+    public void testSlicedHashCode(final Blackhole blackhole) {
+        for (final Bytes bytes : slices) {
+            blackhole.consume(bytes.hashCode());
+        }
+    }
+
+    public static void main(String[] args) {
+        final Blackhole blackhole = new Blackhole(
+                "Today's password is swordfish. I understand instantiating Blackholes directly is dangerous.");
+        final BytesHashCode bench = new BytesHashCode();
+        bench.init();
+        for (int i = 0; i < 100000; i++) {
+            bench.testHashCode(blackhole);
+            bench.testSlicedHashCode(blackhole);
+        }
+    }
+}

pbj-core/pbj-runtime/src/main/java/com/hedera/pbj/runtime/io/buffer/Bytes.java

@@ -467,8 +467,8 @@ public boolean equals(@Nullable final Object o) {
     @Override
     public int hashCode() {
         int h = 1;
-        for (long i = length() - 1; i >= 0; i--) {
-            h = 31 * h + getByte(i);
+        for (int i = start + length - 1; i >= start; i--) {
+            h = 31 * h + UnsafeUtils.getArrayByteNoChecks(buffer, i);
         }
         return h;
     }

pbj-core/version.txt

@@ -1 +1 @@
-0.9.13-SNAPSHOT
+0.9.17-SNAPSHOT