[GitHub] [hadoop-ozone] szetszwo commented on a change in pull request #97: HDDS-2375. Refactor BlockOutputStream to allow flexible buffering.

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szetszwo commented on a change in pull request #97: HDDS-2375. Refactor BlockOutputStream to allow flexible buffering.
URL: https://github.com/apache/hadoop-ozone/pull/97#discussion_r342822304
 
 

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 File path: hadoop-hdds/common/src/main/java/org/apache/hadoop/ozone/common/ChunkBuffer.java
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 @@ -0,0 +1,167 @@
+/*
+ * 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.hadoop.ozone.common;
+
+import org.apache.ratis.thirdparty.com.google.protobuf.ByteString;
+
+import java.nio.ByteBuffer;
+import java.util.Iterator;
+import java.util.function.Function;
+
+/** Buffer for a block chunk. */
+public interface ChunkBuffer {
+  /** {@link ChunkBuffer} implementation using a single {@link ByteBuffer}. */
+  class ImplWithByteBuffer implements ChunkBuffer {
+    private final ByteBuffer buffer;
+
+    private ImplWithByteBuffer(ByteBuffer buffer) {
+      this.buffer = buffer;
+    }
+
+    @Override
+    public int position() {
+      return buffer.position();
+    }
+
+    @Override
+    public int remaining() {
+      return buffer.remaining();
+    }
+
+    @Override
+    public Iterable<ByteBuffer> iterate(int bytesPerChecksum) {
+      return () -> new Iterator<ByteBuffer>() {
+        @Override
+        public boolean hasNext() {
+          return buffer.hasRemaining();
+        }
+
+        @Override
+        public ByteBuffer next() {
+          final ByteBuffer duplicated = buffer.duplicate();
+          final int min = Math.min(
+              buffer.position() + bytesPerChecksum, buffer.limit());
+          duplicated.limit(min);
+          buffer.position(min);
+          return duplicated;
+        }
+      };
+    }
+
+    @Override
+    public ChunkBuffer duplicate(int newPosition, int newLimit) {
+      final ByteBuffer duplicated = buffer.duplicate();
+      duplicated.position(newPosition).limit(newLimit);
+      return new ImplWithByteBuffer(duplicated);
+    }
+
+    @Override
+    public void put(ByteBuffer b) {
+      buffer.put(b);
+    }
+
+    @Override
+    public void clear() {
+      buffer.clear();
+    }
+
+    @Override
+    public ByteString toByteString(Function<ByteBuffer, ByteString> f) {
+      return f.apply(buffer);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+      if (this == obj) {
+        return true;
+      } else if (!(obj instanceof ImplWithByteBuffer)) {
+        return false;
+      }
+      final ImplWithByteBuffer that = (ImplWithByteBuffer)obj;
+      return this.buffer.equals(that.buffer);
+    }
+
+    @Override
+    public int hashCode() {
+      return buffer.hashCode();
+    }
+
+    @Override
+    public String toString() {
+      return getClass().getSimpleName() + ":limit=" + buffer.limit();
+    }
+  }
+
+  /** Similar to {@link ByteBuffer#allocate(int)}. */
+  static ChunkBuffer allocate(int capacity) {
+    return new ImplWithByteBuffer(ByteBuffer.allocate(capacity));
+  }
+
+  /** Warp the given {@link ByteBuffer} as a {@link ChunkBuffer}. */
+  static ChunkBuffer warp(ByteBuffer buffer) {
+    return new ImplWithByteBuffer(buffer);
+  }
+
+  /** Similar to {@link ByteBuffer#position()}. */
+  int position();
+
+  /** Similar to {@link ByteBuffer#remaining()}. */
+  int remaining();
+
+  /** Similar to {@link ByteBuffer#hasRemaining()}. */
+  default boolean hasRemaining() {
+    return remaining() > 0;
+  }
+
+  /** Similar to {@link ByteBuffer#clear()}. */
+  void clear();
+
+  /** Similar to {@link ByteBuffer#put(ByteBuffer)}. */
+  void put(ByteBuffer b);
+
+  /** Similar to {@link ByteBuffer#put(byte[], int, int)}. */
+  default void put(byte[] b, int offset, int length) {
+    put(ByteBuffer.wrap(b, offset, length));
+  }
+
+  /** The same as put(b.asReadOnlyByteBuffer()). */
+  default void put(ByteString b) {
+    put(b.asReadOnlyByteBuffer());
+  }
+
+  /**
+   * Duplicate and then set the position and limit on the duplicated buffer.
+   *
+   * @see ByteBuffer#duplicate()
+   */
+  ChunkBuffer duplicate(int newPosition, int newLimit);
+
+  /**
+   * Iterate the buffer from the current position to the current limit.
+   *
+   * Upon the iteration complete,
+   * the buffer's position will be equal to its limit.
+   */
+  Iterable<ByteBuffer> iterate(int bytesPerChecksum);
+
+  /**
+   * Convert this buffer to a {@link ByteString}.
+   * The position of this buffer remains unchanged.
 
 Review comment:
   It is a bug.  The position should be preserved so that the buffer can be read again for checksum computation.  Thanks.

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