1 /*
2  * Copyright (C) 2014 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://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,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package libcore.net.http;
18 
19 import java.nio.charset.Charset;
20 import java.nio.charset.IllegalCharsetNameException;
21 import java.nio.charset.StandardCharsets;
22 import java.nio.charset.UnsupportedCharsetException;
23 import java.util.Collections;
24 import java.util.HashMap;
25 import java.util.Map;
26 
27 /**
28  * @hide
29  */
30 public class ResponseUtils {
31   /**
32    * Returns the response charset of a HTTP response based on the {@code Content-Type} of
33    * the response (see RFC 7230). If the {@code Content-Type} header is missing or invalid,
34    * the response is assumed to be encoded as {@code UTF-8}. Note that a charset usually
35    * makes sense only for {@code "text/plain"} and other "text based" responses.
36    *
37    * @throws IllegalCharsetNameException if the response specified charset is illegal.
38    * @throws UnsupportedCharsetException if the response specified charset is unsupported.
39    */
responseCharset(String contentTypeHeader)40   public static Charset responseCharset(String contentTypeHeader)
41       throws IllegalCharsetNameException, UnsupportedCharsetException {
42     Charset responseCharset = StandardCharsets.UTF_8;
43     if (contentTypeHeader != null) {
44       Map<String, String> contentTypeParams = parseContentTypeParameters(contentTypeHeader);
45       String charsetParameter = contentTypeParams.get("charset");
46       if (charsetParameter != null) {
47         responseCharset = Charset.forName(charsetParameter);
48       }
49     }
50 
51     return responseCharset;
52   }
53 
54   /**
55    * Parse content-type parameters. The format of this header is roughly :
56    * {@code type/subtype; param1=value1; param2=value2 ...} where each of the
57    * parameters are optional. Parsing is lenient, malformed parameters are ignored.
58    *
59    * Parameter keys & values are trimmed of whitespace and keys are converted to
60    * lower case.
61    */
parseContentTypeParameters(String contentTypeHeader)62   private static Map<String, String> parseContentTypeParameters(String contentTypeHeader) {
63     Map<String, String> parameters = Collections.EMPTY_MAP;
64 
65     String[] fields = contentTypeHeader.split(";");
66     if (fields.length > 1) {
67       parameters = new HashMap<>();
68       // Ignore the first element in the array (the type/subtype).
69       for (int i = 1; i < fields.length; ++i) {
70         final String parameter = fields[i];
71         if (!parameter.isEmpty()) {
72           final String[] components = parameter.split("=");
73           if (components.length != 2) {
74             continue;
75           }
76 
77           final String key = components[0].trim().toLowerCase();
78           final String value = components[1].trim();
79           if (key.isEmpty() || value.isEmpty()) {
80             continue;
81           }
82 
83           parameters.put(key, value);
84         }
85       }
86     }
87 
88     return parameters;
89   }
90 }
91