Github user Ngone51 commented on a diff in the pull request:
https://github.com/apache/spark/pull/19222#discussion_r172010392
--- Diff:
common/unsafe/src/main/java/org/apache/spark/unsafe/memory/OnHeapMemoryBlock.java
---
@@ -0,0 +1,141 @@
+/*
+ * 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.spark.unsafe.memory;
+
+import org.apache.spark.unsafe.Platform;
+
+/**
+ * A consecutive block of memory with a long array on Java heap.
+ */
+public final class OnHeapMemoryBlock extends MemoryBlock {
+
+ private final long[] array;
+
+ public OnHeapMemoryBlock(long[] obj, long offset, long size) {
+ super(obj, offset, size);
+ this.array = obj;
+ assert(offset - Platform.LONG_ARRAY_OFFSET + size <= obj.length * 8L);
+ }
+
+ public OnHeapMemoryBlock(long size) {
+ this(new long[(int)((size + 7) / 8)], Platform.LONG_ARRAY_OFFSET,
+ ((size + 7) / 8) * 8L);
--- End diff --
Should the third param just be ```size```, which is the actual memory size
we can use by ```MemoryBlock```? Though, it may less than the real allocated
memory, which is ```(size + 7) / 8) * 8L```.
And this also decides whether the upper bound is ```size``` or
```array.length * 8L``` in asserts in those getXXX/putXXX methods.
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