Github user NicoK commented on a diff in the pull request:
https://github.com/apache/flink/pull/5105#discussion_r156416892
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/io/network/buffer/BufferBuilder.java
---
@@ -0,0 +1,80 @@
+/*
+ * 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 org.apache.flink.runtime.io.network.buffer;
+
+import org.apache.flink.core.memory.MemorySegment;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+import java.nio.ByteBuffer;
+
+import static org.apache.flink.util.Preconditions.checkNotNull;
+import static org.apache.flink.util.Preconditions.checkState;
+
+/**
+ * Not thread safe class for filling in the initial content of the {@link
Buffer}. Once writing to the builder
+ * is complete, {@link Buffer} instance can be built and shared across
multiple threads.
+ */
+@NotThreadSafe
+public class BufferBuilder {
+ private final MemorySegment memorySegment;
+
+ private final BufferRecycler recycler;
+
+ private int position = 0;
+
+ private boolean built = false;
--- End diff --
Can't we use the `position` field and set it to an invalid valid, e.g.
`-1`, instead? This is just to allow an internal check for correctness.
---
