zxingorg/src/com/google/zxing/web/IPTrie.java

   1 /*\r
   2  * Copyright 2008 Google Inc.\r
   3  *\r
   4  * Licensed under the Apache License, Version 2.0 (the "License");\r
   5  * you may not use this file except in compliance with the License.\r
   6  * You may obtain a copy of the License at\r
   7  *\r
   8  *      http://www.apache.org/licenses/LICENSE-2.0\r
   9  *\r
  10  * Unless required by applicable law or agreed to in writing, software\r
  11  * distributed under the License is distributed on an "AS IS" BASIS,\r
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
  13  * See the License for the specific language governing permissions and\r
  14  * limitations under the License.\r
  15  */\r
  16 \r
  17 package com.google.zxing.web;\r
  18 \r
  19 import java.net.InetAddress;\r
  20 import java.util.Arrays;\r
  21 \r
  22 /**\r
  23  * @author Sean Owen\r
  24  */\r
  25 final class IPTrie {\r
  26 \r
  27         private final IPTrieNode root;\r
  28 \r
  29         IPTrie() {\r
  30                 root = new IPTrieNode(false);\r
  31         }\r
  32 \r
  33         int incrementAndGet(InetAddress ipAddress) {\r
  34                 byte[] octets = ipAddress.getAddress();\r
  35                 synchronized (root) {\r
  36                         IPTrieNode current = root;\r
  37                         int max = octets.length - 1;\r
  38                         for (int offset = 0; offset < max; offset++) {\r
  39                                 int index = 0xFF & octets[offset];\r
  40                                 IPTrieNode child = current.children[index];\r
  41                                 if (child == null) {\r
  42                                         child = new IPTrieNode(offset == max - 1);\r
  43                                         current.children[index] = child;\r
  44                                 }\r
  45                                 current = child;\r
  46                         }\r
  47                         int index = 0xFF & octets[max];\r
  48                         current.values[index]++;\r
  49                         return current.values[index];\r
  50                 }\r
  51         }\r
  52 \r
  53         void clear() {\r
  54                 synchronized (root) {\r
  55                         Arrays.fill(root.children, null);\r
  56                 }\r
  57         }\r
  58 \r
  59         private static final class IPTrieNode {\r
  60                 final IPTrieNode[] children;\r
  61                 final int[] values;\r
  62                 private IPTrieNode(boolean terminal) {\r
  63                         if (terminal) {\r
  64                                 children = null;\r
  65                                 values = new int[256];\r
  66                         } else {\r
  67                                 children = new IPTrieNode[256];\r
  68                                 values = null;\r
  69                         }\r
  70                 }\r
  71         }\r
  72 \r
  73 }