Readded BytesReferenceSerializer impl as ICacheKeySerializerTests dep…

…ended on it

Signed-off-by: Peter Alfonsi <petealft@amazon.com>

server/src/main/java/org/opensearch/common/cache/tier/BytesReferenceSerializer.java

@@ -0,0 +1,42 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.cache.tier;
+
+import org.opensearch.core.common.bytes.BytesArray;
+import org.opensearch.core.common.bytes.BytesReference;
+
+import java.util.Arrays;
+
+/**
+ * A serializer which transforms BytesReference to byte[].
+ * The type of BytesReference is NOT preserved after deserialization, but nothing in opensearch should care.
+ */
+public class BytesReferenceSerializer implements Serializer<BytesReference, byte[]> {
+    // This class does not get passed to ehcache itself, so it's not required that classes match after deserialization.
+
+    public BytesReferenceSerializer() {}
+
+    @Override
+    public byte[] serialize(BytesReference object) {
+        return BytesReference.toBytes(object);
+    }
+
+    @Override
+    public BytesReference deserialize(byte[] bytes) {
+        if (bytes == null) {
+            return null;
+        }
+        return new BytesArray(bytes);
+    }
+
+    @Override
+    public boolean equals(BytesReference object, byte[] bytes) {
+        return Arrays.equals(serialize(object), bytes);
+    }
+}

server/src/test/java/org/opensearch/common/cache/tier/BytesReferenceSerializerTests.java

@@ -0,0 +1,67 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.cache.tier;
+
+import org.opensearch.common.Randomness;
+import org.opensearch.common.bytes.ReleasableBytesReference;
+import org.opensearch.common.util.BigArrays;
+import org.opensearch.common.util.PageCacheRecycler;
+import org.opensearch.core.common.bytes.BytesArray;
+import org.opensearch.core.common.bytes.BytesReference;
+import org.opensearch.core.common.bytes.CompositeBytesReference;
+import org.opensearch.core.common.util.ByteArray;
+import org.opensearch.test.OpenSearchTestCase;
+
+import java.util.Random;
+
+public class BytesReferenceSerializerTests extends OpenSearchTestCase {
+    public void testEquality() throws Exception {
+        BytesReferenceSerializer ser = new BytesReferenceSerializer();
+        // Test that values are equal before and after serialization, for each implementation of BytesReference.
+        byte[] bytesValue = new byte[1000];
+        Random rand = Randomness.get();
+        rand.nextBytes(bytesValue);
+
+        BytesReference ba = new BytesArray(bytesValue);
+        byte[] serialized = ser.serialize(ba);
+        assertTrue(ser.equals(ba, serialized));
+        BytesReference deserialized = ser.deserialize(serialized);
+        assertEquals(ba, deserialized);
+
+        ba = new BytesArray(new byte[] {});
+        serialized = ser.serialize(ba);
+        assertTrue(ser.equals(ba, serialized));
+        deserialized = ser.deserialize(serialized);
+        assertEquals(ba, deserialized);
+
+        BytesReference cbr = CompositeBytesReference.of(new BytesArray(bytesValue), new BytesArray(bytesValue));
+        serialized = ser.serialize(cbr);
+        assertTrue(ser.equals(cbr, serialized));
+        deserialized = ser.deserialize(serialized);
+        assertEquals(cbr, deserialized);
+
+        // We need the PagedBytesReference to be larger than the page size (16 KB) in order to actually create it
+        byte[] pbrValue = new byte[PageCacheRecycler.PAGE_SIZE_IN_BYTES * 2];
+        rand.nextBytes(pbrValue);
+        ByteArray arr = BigArrays.NON_RECYCLING_INSTANCE.newByteArray(pbrValue.length);
+        arr.set(0L, pbrValue, 0, pbrValue.length);
+        assert !arr.hasArray();
+        BytesReference pbr = BytesReference.fromByteArray(arr, pbrValue.length);
+        serialized = ser.serialize(pbr);
+        assertTrue(ser.equals(pbr, serialized));
+        deserialized = ser.deserialize(serialized);
+        assertEquals(pbr, deserialized);
+
+        BytesReference rbr = new ReleasableBytesReference(new BytesArray(bytesValue), ReleasableBytesReference.NO_OP);
+        serialized = ser.serialize(rbr);
+        assertTrue(ser.equals(rbr, serialized));
+        deserialized = ser.deserialize(serialized);
+        assertEquals(rbr, deserialized);
+    }
+}