Create a new ByteStore when writing zero sized arrays. Fix #384

src/main/java/net/openhft/chronicle/bytes/NativeBytes.java

@@ -17,7 +17,9 @@
  */
 package net.openhft.chronicle.bytes;
 
+import net.openhft.chronicle.bytes.internal.EmptyByteStore;
 import net.openhft.chronicle.bytes.internal.ReferenceCountedUtil;
+import net.openhft.chronicle.bytes.internal.SingletonEmptyByteStore;
 import net.openhft.chronicle.bytes.util.DecoratedBufferOverflowException;
 import net.openhft.chronicle.core.Jvm;
 import net.openhft.chronicle.core.Maths;
@@ -57,8 +59,7 @@ public NativeBytes(@NotNull final BytesStore store, @NonNegative final long capa
 
     public NativeBytes(@NotNull final BytesStore store)
             throws IllegalStateException, IllegalArgumentException {
-        super(store, 0, store.capacity());
-        capacity = store.capacity();
+        this(store, store.capacity());
     }
 
     /**
@@ -160,7 +161,8 @@ protected void writeCheckOffset(final @NonNegative long offset, final @NonNegati
             throws BufferOverflowException, IllegalStateException {
         if (offset >= bytesStore.start() && offset + adding >= bytesStore.start()) {
             final long writeEnd = offset + adding;
-            if (writeEnd <= bytesStore.safeLimit()) {
+            // Always resize if we are backed by a SingletonEmptyByteStore as this is shared and does not provide all functionality
+            if (writeEnd <= bytesStore.safeLimit() && !(EmptyByteStore.class.isInstance(bytesStore))) {
                 return; // do nothing.
             }
             if (writeEnd >= capacity)
@@ -226,7 +228,7 @@ private void resize(@NonNegative final long endOfBuffer)
         if (endOfBuffer > capacity())
             throw new DecoratedBufferOverflowException(endOfBuffer + ">" + capacity());
         final long realCapacity = realCapacity();
-        if (endOfBuffer <= realCapacity) {
+        if (endOfBuffer <= realCapacity && !(EmptyByteStore.class.isInstance(bytesStore))) {
             //  No resize
             return;
         }

src/test/java/net/openhft/chronicle/bytes/issue/Issue384ReplaceByteStoreOnEmptyArrayTest.java

@@ -0,0 +1,68 @@
+/*
+ * Copyright (c) 2016-2022 chronicle.software
+ *
+ * https://chronicle.software
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package net.openhft.chronicle.bytes.issue;
+
+import net.openhft.chronicle.bytes.Bytes;
+import net.openhft.chronicle.bytes.VanillaBytes;
+import net.openhft.chronicle.bytes.internal.EmptyByteStore;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.stream.Stream;
+
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+final class Issue384ReplaceByteStoreOnEmptyArrayTest {
+
+    @ParameterizedTest(name = "{index}: ({0})")
+    @MethodSource("bytesToTest")
+    void reproduce(String classSimpleName, Bytes<?> bytes) {
+
+        // throwing AssertionErrors in the code makes testing more complicated.
+        boolean replacedOrRefused = false;
+        try {
+            // Write an empty array into the empty bytes. This should trigger a
+            // resize since the empty bytes is using a shared backing EmptyByteStore.
+            bytes.write(new byte[0]);
+            // Make sure we are not using an EmptyByteStore
+            replacedOrRefused = !(bytes.bytesStore() instanceof EmptyByteStore);
+        } catch (AssertionError ignored) {
+            // This is ok as some of the Bytes objects are not elastic.
+            replacedOrRefused = true;
+        } finally {
+            bytes.releaseLast();
+        }
+        assertTrue(replacedOrRefused);
+    }
+
+    static Stream<Arguments> bytesToTest() {
+        return Stream.of(
+                        Bytes.allocateElasticDirect(),
+                        Bytes.allocateElasticDirect(0),
+                        Bytes.allocateDirect(0),
+                        Bytes.allocateElasticOnHeap(0),
+                        VanillaBytes.vanillaBytes(),
+                        Bytes.from(""),
+                        Bytes.allocateDirect(new byte[0]),
+                        Bytes.fromDirect("")
+                )
+                .map(b -> Arguments.of(b.getClass().getSimpleName() + (b.isElastic() ? " Elastic" : " Fixed"), b));
+    }
+
+}