[GitHub] [hbase] chenxu14 commented on a change in pull request #581: HBASE-22888 Share some stuffs with the initial reader when new stream reader created

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chenxu14 commented on a change in pull request #581: HBASE-22888 Share some stuffs with the initial reader when new stream reader created
URL: https://github.com/apache/hbase/pull/581#discussion_r330513774
 
 

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 File path: hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFilePreadReader.java
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+/**
+ * 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.hbase.io.hfile;
+
+import java.io.IOException;
+import java.security.Key;
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.hbase.io.crypto.Cipher;
+import org.apache.hadoop.hbase.io.crypto.Encryption;
+import org.apache.hadoop.hbase.io.hfile.HFile.FileInfo;
+import org.apache.hadoop.hbase.io.hfile.HFile.Reader;
+import org.apache.hadoop.hbase.security.EncryptionUtil;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.yetus.audience.InterfaceAudience;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Implementation of {@link HFile.Reader} to deal with pread.
+ */
+@InterfaceAudience.Private
+public class HFilePreadReader extends HFileReaderImpl {
+  private static final Logger LOG = LoggerFactory.getLogger(HFileReaderImpl.class);
+
+  /**
+   * The iterator will track all blocks in load-on-open section, since we use the
+   * {@link org.apache.hadoop.hbase.io.ByteBuffAllocator} to manage the ByteBuffers in block now,
+   * so we must ensure that deallocate all ByteBuffers in the end.
+   */
+  private final HFileBlock.BlockIterator blockIter;
+
+  public HFilePreadReader(ReaderContext context, FixedFileTrailer trailer,
+      CacheConfig cacheConf, Configuration conf) throws IOException {
+    super(context, cacheConf, conf);
+    this.trailer = trailer;
+    this.compressAlgo = trailer.getCompressionCodec();
+    // Comparator class name is stored in the trailer in version 2.
+    this.comparator = trailer.createComparator();
+    checkFileVersion();
+    this.hfileContext = createHFileContext(context, trailer, conf);
+    this.fsBlockReader = new HFileBlock.FSReaderImpl(context, hfileContext,
+        cacheConf.getByteBuffAllocator());
+    // Initialize an block iterator, and parse load-on-open blocks in the following.
+    this.blockIter = fsBlockReader.blockRange(trailer.getLoadOnOpenDataOffset(),
+      fileSize - trailer.getTrailerSize());
+
+    dataBlockIndexReader = new HFileBlockIndex.CellBasedKeyBlockIndexReader(comparator,
+        trailer.getNumDataIndexLevels());
+    metaBlockIndexReader = new HFileBlockIndex.ByteArrayKeyBlockIndexReader(1);
+    // Data index. We also read statistics about the block index written after
+    // the root level.
+    dataBlockIndexReader.readMultiLevelIndexRoot(
+        blockIter.nextBlockWithBlockType(BlockType.ROOT_INDEX),
+        trailer.getDataIndexCount());
+    // Meta index.
+    metaBlockIndexReader.readRootIndex(
+        blockIter.nextBlockWithBlockType(BlockType.ROOT_INDEX),
+        trailer.getMetaIndexCount());
+    loadFileInfo();
 
 Review comment:
   Move the code to HFileInfo

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