hbase-common/src/main/java/org/apache/hadoop/hbase/util/Order.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.util;
  19
  20 import org.apache.yetus.audience.InterfaceAudience;
  21
  22 /**
  23  * Used to describe or modify the lexicographical sort order of a
  24  * {@code byte[]}. Default ordering is considered {@code ASCENDING}. The order
  25  * of a {@code byte[]} can be inverted, resulting in {@code DESCENDING} order,
  26  * by replacing each byte with its 1's compliment.
  27  */
  28 @InterfaceAudience.Public
  29 public enum Order {
  30   ASCENDING {
  31     @Override
  32     public int cmp(int cmp) {
  33       /* noop */ return cmp;
  34     }
  35
  36     @Override
  37     public byte apply(byte val) {
  38       /* noop */ return val;
  39     }
  40
  41     @Override
  42     public void apply(byte[] val) {
  43       /* noop */
  44     }
  45
  46     @Override
  47     public void apply(byte[] val, int offset, int length) {
  48       /* noop */
  49     }
  50
  51     @Override
  52     public String toString() {
  53       return "ASCENDING";
  54     }
  55   },
  56
  57   DESCENDING {
  58     /**
  59      * A {@code byte} value is inverted by taking its 1's Complement, achieved
  60      * via {@code xor} with {@code 0xff}.
  61      */
  62     private static final byte MASK = (byte) 0xff;
  63
  64     @Override
  65     public int cmp(int cmp) {
  66       return -1 * cmp;
  67     }
  68
  69     @Override
  70     public byte apply(byte val) {
  71       return (byte) (val ^ MASK);
  72     }
  73
  74     @Override
  75     public void apply(byte[] val) {
  76       for (int i = 0; i < val.length; i++) {
  77         val[i] ^= MASK;
  78       }
  79     }
  80
  81     @Override
  82     public void apply(byte[] val, int offset, int length) {
  83       for (int i = 0; i < length; i++) {
  84         val[offset + i] ^= MASK;
  85       }
  86     }
  87
  88     @Override
  89     public String toString() {
  90       return "DESCENDING";
  91     }
  92   };
  93
  94   /**
  95    * Returns the adjusted trichotomous value according to the ordering imposed by this
  96    * {@code Order}.
  97    */
  98   public abstract int cmp(int cmp);
  99
 100   /**
 101    * Apply order to the byte {@code val}.
 102    */
 103   public abstract byte apply(byte val);
 104
 105   /**
 106    * Apply order to the byte array {@code val}.
 107    */
 108   public abstract void apply(byte[] val);
 109
 110   /**
 111    * Apply order to a range within the byte array {@code val}.
 112    */
 113   public abstract void apply(byte[] val, int offset, int length);
 114 }