[Java] add buffer callback

java/fury-core/src/main/java/io/fury/serializer/BufferCallback.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2023 The Fury authors
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 io.fury.serializer;
+
+/**
+ * If the callback returns false, the given buffer is out-of-band; otherwise the buffer is
+ * serialized in-band, i.e. inside the serialized stream.
+ */
+@FunctionalInterface
+public interface BufferCallback {
+
+  boolean apply(BufferObject object);
+}

java/fury-core/src/main/java/io/fury/serializer/BufferObject.java

@@ -0,0 +1,71 @@
+/*
+ * Copyright 2023 The Fury authors
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 io.fury.serializer;
+
+import io.fury.memory.MemoryBuffer;
+import java.nio.ByteBuffer;
+import java.nio.ByteOrder;
+
+/**
+ * Fury serialized representation of an object. Note: This class is used for zero-copy out-of-band
+ * serialization and shouldn't be used for any other cases.
+ *
+ * @see ByteBufferBufferObject // * @see Serializers.PrimitiveArrayBufferObject
+ */
+public interface BufferObject {
+
+  int totalBytes();
+
+  /**
+   * Write serialized object to buffer. Note: The caller should try to ensure `buffer.writerIndex`
+   * is aligned, otherwise the memory copy will be inefficient.
+   */
+  void writeTo(MemoryBuffer buffer);
+
+  /** Write serialized data as Buffer. */
+  MemoryBuffer toBuffer();
+
+  final class ByteBufferBufferObject implements BufferObject {
+    private final ByteBuffer buffer;
+
+    public ByteBufferBufferObject(ByteBuffer buffer) {
+      this.buffer = buffer;
+    }
+
+    @Override
+    public int totalBytes() {
+      return buffer.remaining() + 1;
+    }
+
+    /** Writes a byte representing the byte order. */
+    @Override
+    public void writeTo(MemoryBuffer buffer) {
+      // `writeByte` may make writerIndex not aligned, so write data first instead.
+      buffer.write(this.buffer.duplicate());
+      buffer.writeByte(this.buffer.order() == ByteOrder.BIG_ENDIAN ? (byte) 1 : 0);
+    }
+
+    @Override
+    public MemoryBuffer toBuffer() {
+      MemoryBuffer buffer = MemoryBuffer.newHeapBuffer(totalBytes());
+      writeTo(buffer);
+      return buffer.slice(0, buffer.writerIndex());
+    }
+  }
+}