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
17package libcore.net.http;
18
19import java.nio.charset.Charset;
20import java.nio.charset.IllegalCharsetNameException;
21import java.nio.charset.StandardCharsets;
22import java.nio.charset.UnsupportedCharsetException;
23import java.util.Collections;
24import java.util.HashMap;
25import java.util.Map;
26
27/**
28 * @hide
29 */
30public 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   */
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   */
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