hbase-client/src/main/java/org/apache/hadoop/hbase/protobuf/ProtobufMagic.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.protobuf;
  19
  20 import org.apache.yetus.audience.InterfaceAudience;
  21
  22 /**
  23  * Protobufs utility.
  24  */
  25 @InterfaceAudience.Private
  26 public class ProtobufMagic {
  27
  28   private ProtobufMagic() {
  29   }
  30
  31   /**
  32    * Magic we put ahead of a serialized protobuf message.
  33    * For example, all znode content is protobuf messages with the below magic
  34    * for preamble.
  35    */
  36   public static final byte [] PB_MAGIC = new byte [] {'P', 'B', 'U', 'F'};
  37
  38   /**
  39    * @param bytes Bytes to check.
  40    * @return True if passed <code>bytes</code> has {@link #PB_MAGIC} for a prefix.
  41    */
  42   public static boolean isPBMagicPrefix(final byte [] bytes) {
  43     if (bytes == null) return false;
  44     return isPBMagicPrefix(bytes, 0, bytes.length);
  45   }
  46
  47   /*
  48    * Copied from Bytes.java to here
  49    * hbase-common now depends on hbase-protocol
  50    * Referencing Bytes.java directly would create circular dependency
  51    */
  52   private static int compareTo(byte[] buffer1, int offset1, int length1,
  53       byte[] buffer2, int offset2, int length2) {
  54     // Short circuit equal case
  55     if (buffer1 == buffer2 &&
  56         offset1 == offset2 &&
  57         length1 == length2) {
  58       return 0;
  59     }
  60     // Bring WritableComparator code local
  61     int end1 = offset1 + length1;
  62     int end2 = offset2 + length2;
  63     for (int i = offset1, j = offset2; i < end1 && j < end2; i++, j++) {
  64       int a = (buffer1[i] & 0xff);
  65       int b = (buffer2[j] & 0xff);
  66       if (a != b) {
  67         return a - b;
  68       }
  69     }
  70     return length1 - length2;
  71   }
  72
  73   /**
  74    * @param bytes Bytes to check.
  75    * @param offset offset to start at
  76    * @param len length to use
  77    * @return True if passed <code>bytes</code> has {@link #PB_MAGIC} for a prefix.
  78    */
  79   public static boolean isPBMagicPrefix(final byte [] bytes, int offset, int len) {
  80     if (bytes == null || len < PB_MAGIC.length) return false;
  81     return compareTo(PB_MAGIC, 0, PB_MAGIC.length, bytes, offset, PB_MAGIC.length) == 0;
  82   }
  83
  84   /**
  85    * @return Length of {@link #PB_MAGIC}
  86    */
  87   public static int lengthOfPBMagic() {
  88     return PB_MAGIC.length;
  89   }
  90 }