[GitHub] [arrow] jacques-n commented on a change in pull request #7030: ARROW-7808: [Java][Dataset] Implement Datasets Java API by JNI to C++

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jacques-n commented on a change in pull request #7030:
URL: https://github.com/apache/arrow/pull/7030#discussion_r449967588



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File path: java/dataset/src/main/java/org/apache/arrow/memory/NativeUnderlingMemory.java
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@@ -0,0 +1,65 @@
+/*
+ * 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.arrow.memory;
+
+import org.apache.arrow.dataset.jni.JniWrapper;
+
+/**
+ * AllocationManager implementation for Native allocated memory.
+ */
+public class NativeUnderlingMemory extends AllocationManager {

Review comment:
       Not necessarily. When you allocate and deallocate memory in c++ you can call (via reflection) java.nio.Bits.reserveMemory() and unreserveMemory(). If you wanted to be extra fancy you could actually just do the reads/writes to the underlying atomics. Alternatively, you could build a pooling impl for C++ that uses the JNIEnv. NewDirectByteBuffer.




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