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1   /*
2    * Copyright 2014 The Netty Project
3    *
4    * The Netty Project licenses this file to you under the Apache License,
5    * version 2.0 (the "License"); you may not use this file except in compliance
6    * with the License. You may obtain a copy of the License at:
7    *
8    *   https://www.apache.org/licenses/LICENSE-2.0
9    *
10   * Unless required by applicable law or agreed to in writing, software
11   * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12   * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13   * License for the specific language governing permissions and limitations
14   * under the License.
15   */
16  package io.netty.handler.codec.http.websocketx.extensions;
17  
18  import io.netty.handler.codec.http.HttpHeaderNames;
19  import io.netty.handler.codec.http.HttpHeaderValues;
20  import io.netty.handler.codec.http.HttpHeaders;
21  
22  import java.util.ArrayList;
23  import java.util.Collections;
24  import java.util.HashMap;
25  import java.util.List;
26  import java.util.Map;
27  import java.util.Map.Entry;
28  import java.util.regex.Matcher;
29  import java.util.regex.Pattern;
30  
31  public final class WebSocketExtensionUtil {
32  
33      private static final String EXTENSION_SEPARATOR = ",";
34      private static final String PARAMETER_SEPARATOR = ";";
35      private static final char PARAMETER_EQUAL = '=';
36  
37      private static final Pattern PARAMETER = Pattern.compile("^([^=]+)(=[\\\"]?([^\\\"]+)[\\\"]?)?$");
38  
39      static boolean isWebsocketUpgrade(HttpHeaders headers) {
40          //this contains check does not allocate an iterator, and most requests are not upgrades
41          //so we do the contains check first before checking for specific values
42          return headers.contains(HttpHeaderNames.UPGRADE) &&
43                  headers.containsValue(HttpHeaderNames.CONNECTION, HttpHeaderValues.UPGRADE, true) &&
44                  headers.contains(HttpHeaderNames.UPGRADE, HttpHeaderValues.WEBSOCKET, true);
45      }
46  
47      public static List<WebSocketExtensionData> extractExtensions(String extensionHeader) {
48          String[] rawExtensions = extensionHeader.split(EXTENSION_SEPARATOR);
49          if (rawExtensions.length > 0) {
50              List<WebSocketExtensionData> extensions = new ArrayList<WebSocketExtensionData>(rawExtensions.length);
51              for (String rawExtension : rawExtensions) {
52                  String[] extensionParameters = rawExtension.split(PARAMETER_SEPARATOR);
53                  String name = extensionParameters[0].trim();
54                  Map<String, String> parameters;
55                  if (extensionParameters.length > 1) {
56                      parameters = new HashMap<String, String>(extensionParameters.length - 1);
57                      for (int i = 1; i < extensionParameters.length; i++) {
58                          String parameter = extensionParameters[i].trim();
59                          Matcher parameterMatcher = PARAMETER.matcher(parameter);
60                          if (parameterMatcher.matches() && parameterMatcher.group(1) != null) {
61                              parameters.put(parameterMatcher.group(1), parameterMatcher.group(3));
62                          }
63                      }
64                  } else {
65                      parameters = Collections.emptyMap();
66                  }
67                  extensions.add(new WebSocketExtensionData(name, parameters));
68              }
69              return extensions;
70          } else {
71              return Collections.emptyList();
72          }
73      }
74  
75      static String computeMergeExtensionsHeaderValue(String userDefinedHeaderValue,
76                                                      List<WebSocketExtensionData> extraExtensions) {
77          List<WebSocketExtensionData> userDefinedExtensions =
78            userDefinedHeaderValue != null ?
79              extractExtensions(userDefinedHeaderValue) :
80              Collections.<WebSocketExtensionData>emptyList();
81  
82          for (WebSocketExtensionData userDefined: userDefinedExtensions) {
83              WebSocketExtensionData matchingExtra = null;
84              int i;
85              for (i = 0; i < extraExtensions.size(); i ++) {
86                  WebSocketExtensionData extra = extraExtensions.get(i);
87                  if (extra.name().equals(userDefined.name())) {
88                      matchingExtra = extra;
89                      break;
90                  }
91              }
92              if (matchingExtra == null) {
93                  extraExtensions.add(userDefined);
94              } else {
95                  // merge with higher precedence to user defined parameters
96                  Map<String, String> mergedParameters = new HashMap<String, String>(matchingExtra.parameters());
97                  mergedParameters.putAll(userDefined.parameters());
98                  extraExtensions.set(i, new WebSocketExtensionData(matchingExtra.name(), mergedParameters));
99              }
100         }
101 
102         StringBuilder sb = new StringBuilder(150);
103 
104         for (WebSocketExtensionData data: extraExtensions) {
105             sb.append(data.name());
106             for (Entry<String, String> parameter : data.parameters().entrySet()) {
107                 sb.append(PARAMETER_SEPARATOR);
108                 sb.append(parameter.getKey());
109                 if (parameter.getValue() != null) {
110                     sb.append(PARAMETER_EQUAL);
111                     sb.append(parameter.getValue());
112                 }
113             }
114             sb.append(EXTENSION_SEPARATOR);
115         }
116 
117         if (!extraExtensions.isEmpty()) {
118             sb.setLength(sb.length() - EXTENSION_SEPARATOR.length());
119         }
120 
121         return sb.toString();
122     }
123 
124     private WebSocketExtensionUtil() {
125         // Unused
126     }
127 }