1 /*
2  * Copyright (C) 2011 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 dalvik.annotation.compat.UnsupportedAppUsage;
20 import java.text.DateFormat;
21 import java.text.ParseException;
22 import java.text.SimpleDateFormat;
23 import java.util.Date;
24 import java.util.Locale;
25 import java.util.TimeZone;
26 
27 /**
28  * Best-effort parser for HTTP dates.
29  */
30 public final class HttpDate {
31 
32     /**
33      * Most websites serve cookies in the blessed format. Eagerly create the parser to ensure such
34      * cookies are on the fast path.
35      */
36     private static final ThreadLocal<DateFormat> STANDARD_DATE_FORMAT
37             = new ThreadLocal<DateFormat>() {
38         @Override protected DateFormat initialValue() {
39             DateFormat rfc1123 = new SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss zzz", Locale.US);
40             rfc1123.setTimeZone(TimeZone.getTimeZone("UTC"));
41             return rfc1123;
42         }
43     };
44 
45     /**
46      * If we fail to parse a date in a non-standard format, try each of these formats in sequence.
47      */
48     private static final String[] BROWSER_COMPATIBLE_DATE_FORMATS = new String[] {
49             /* This list comes from  {@code org.apache.http.impl.cookie.BrowserCompatSpec}. */
50             "EEEE, dd-MMM-yy HH:mm:ss zzz", // RFC 1036
51             "EEE MMM d HH:mm:ss yyyy", // ANSI C asctime()
52             "EEE, dd-MMM-yyyy HH:mm:ss z",
53             "EEE, dd-MMM-yyyy HH-mm-ss z",
54             "EEE, dd MMM yy HH:mm:ss z",
55             "EEE dd-MMM-yyyy HH:mm:ss z",
56             "EEE dd MMM yyyy HH:mm:ss z",
57             "EEE dd-MMM-yyyy HH-mm-ss z",
58             "EEE dd-MMM-yy HH:mm:ss z",
59             "EEE dd MMM yy HH:mm:ss z",
60             "EEE,dd-MMM-yy HH:mm:ss z",
61             "EEE,dd-MMM-yyyy HH:mm:ss z",
62             "EEE, dd-MM-yyyy HH:mm:ss z",
63 
64             /* RI bug 6641315 claims a cookie of this format was once served by www.yahoo.com */
65             "EEE MMM d yyyy HH:mm:ss z",
66     };
67 
68     /**
69      * Returns the date for {@code value}. Returns null if the value couldn't be
70      * parsed.
71      */
72     @UnsupportedAppUsage
parse(String value)73     public static Date parse(String value) {
74         try {
75             return STANDARD_DATE_FORMAT.get().parse(value);
76         } catch (ParseException ignore) {
77         }
78         for (String formatString : BROWSER_COMPATIBLE_DATE_FORMATS) {
79             try {
80                 return new SimpleDateFormat(formatString, Locale.US).parse(value);
81             } catch (ParseException ignore) {
82             }
83         }
84         return null;
85     }
86 
87     /**
88      * Returns the string for {@code value}.
89      */
90     @UnsupportedAppUsage
format(Date value)91     public static String format(Date value) {
92         return STANDARD_DATE_FORMAT.get().format(value);
93     }
94 }
95