HBASE-17332 Replace HashMap to Array for DataBlockEncoding.idToEncoding

hbase-common/src/main/java/org/apache/hadoop/hbase/io/encoding/DataBlockEncoding.java

@@ -18,8 +18,6 @@ package org.apache.hadoop.hbase.io.encoding;
 
 import java.io.IOException;
 import java.io.OutputStream;
-import java.util.HashMap;
-import java.util.Map;
 
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
 import org.apache.hadoop.hbase.classification.InterfaceStability;
@@ -54,24 +52,21 @@ public enum DataBlockEncoding {
   public static final int ID_SIZE = Bytes.SIZEOF_SHORT;
 
   /** Maps data block encoding ids to enum instances. */
-  private static Map<Short, DataBlockEncoding> idToEncoding =
+  private static DataBlockEncoding[] idArray = new DataBlockEncoding[Byte.MAX_VALUE + 1];
-      new HashMap<Short, DataBlockEncoding>();
 
   static {
     for (DataBlockEncoding algo : values()) {
-      if (idToEncoding.containsKey(algo.id)) {
+      if (idArray[algo.id] != null) {
         throw new RuntimeException(String.format(
-            "Two data block encoder algorithms '%s' and '%s' have " +
+          "Two data block encoder algorithms '%s' and '%s' have " + "the same id %d",
-            "the same id %d",
+          idArray[algo.id].toString(), algo.toString(), (int) algo.id));
-            idToEncoding.get(algo.id).toString(), algo.toString(),
-            (int) algo.id));
       }
-      idToEncoding.put(algo.id, algo);
+      idArray[algo.id] = algo;
     }
   }
 
   private DataBlockEncoding(int id, String encoderClsName) {
-    if (id < Short.MIN_VALUE || id > Short.MAX_VALUE) {
+    if (id < 0 || id > Byte.MAX_VALUE) {
       throw new AssertionError(
           "Data block encoding algorithm id is out of range: " + id);
     }
@@ -139,13 +134,7 @@ public enum DataBlockEncoding {
    * @return Newly created data block encoder.
    */
   public static DataBlockEncoder getDataBlockEncoderById(short encoderId) {
-    if (!idToEncoding.containsKey(encoderId)) {
+    return getEncodingById(encoderId).getEncoder();
-      throw new IllegalArgumentException(String.format(
-          "There is no data block encoder for given id '%d'",
-          (int) encoderId));
-    }
-
-    return idToEncoding.get(encoderId).getEncoder();
   }
 
   /**
@@ -154,7 +143,7 @@ public enum DataBlockEncoding {
    * @return name, same as used in options in column family
    */
   public static String getNameFromId(short encoderId) {
-    return idToEncoding.get(encoderId).toString();
+    return getEncodingById(encoderId).toString();
   }
 
   /**
@@ -167,19 +156,22 @@ public enum DataBlockEncoding {
    */
   public static boolean isCorrectEncoder(DataBlockEncoder encoder,
       short encoderId) {
-    if (!idToEncoding.containsKey(encoderId)) {
+    DataBlockEncoding algorithm = getEncodingById(encoderId);
-      throw new IllegalArgumentException(String.format(
-          "There is no data block encoder for given id '%d'",
-          (int) encoderId));
-    }
-
-    DataBlockEncoding algorithm = idToEncoding.get(encoderId);
     String encoderCls = encoder.getClass().getName();
     return encoderCls.equals(algorithm.encoderCls);
   }
 
   public static DataBlockEncoding getEncodingById(short dataBlockEncodingId) {
-    return idToEncoding.get(dataBlockEncodingId);
+    DataBlockEncoding algorithm = null;
+    if (dataBlockEncodingId >= 0 && dataBlockEncodingId <= Byte.MAX_VALUE) {
+      algorithm = idArray[dataBlockEncodingId];
+    }
+    if (algorithm == null) {
+      throw new IllegalArgumentException(String.format(
+          "There is no data block encoder for given id '%d'",
+          (int) dataBlockEncodingId));
+    }
+    return algorithm;
   }
 
   protected static DataBlockEncoder createEncoder(String fullyQualifiedClassName){

hbase-server/src/test/java/org/apache/hadoop/hbase/io/encoding/TestDataBlockEncoding.java

@@ -0,0 +1,50 @@
+/*
+ * 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.encoding;
+
+import static org.junit.Assert.assertTrue;
+import static org.junit.Assert.fail;
+
+import org.apache.hadoop.hbase.testclassification.SmallTests;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+@Category(SmallTests.class)
+public class TestDataBlockEncoding {
+
+  @Test
+  public void testGetDataBlockEncoder() throws Exception {
+    for (DataBlockEncoding algo : DataBlockEncoding.values()) {
+      DataBlockEncoder encoder = DataBlockEncoding.getDataBlockEncoderById(algo.getId());
+      if (algo.getId() != 0) {
+        assertTrue(DataBlockEncoding.isCorrectEncoder(encoder, algo.getId()));
+      }
+    }
+    try {
+      DataBlockEncoding.getDataBlockEncoderById((short) -1);
+      fail("Illegal encoderId, should get IllegalArgumentException.");
+    } catch (IllegalArgumentException ie) {
+    }
+    try {
+      DataBlockEncoding.getDataBlockEncoderById(Byte.MAX_VALUE);
+      // fail because idArray[Byte.MAX_VALUE] = null
+      fail("Illegal encoderId, should get IllegalArgumentException.");
+    } catch (IllegalArgumentException ie) {
+    }
+  }
+
+}