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 /*

  * ====================================================================

  * Licensed to the Apache Software Foundation (ASF) under one

  * or more contributor license agreements.  See the NOTICE file

  * distributed with this work for additional information

  * regarding copyright ownership.  The ASF licenses this file

  * to you under the Apache License, Version 2.0 (the

  * "License"); you may not use this file except in compliance

  * with the License.  You may obtain a copy of the License at

  *

  *   http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing,

  * software distributed under the License is distributed on an

  * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY

  * KIND, either express or implied.  See the License for the

  * specific language governing permissions and limitations

  * under the License.

  * ====================================================================

  *

  * This software consists of voluntary contributions made by many

  * individuals on behalf of the Apache Software Foundation.  For more

  * information on the Apache Software Foundation, please see

  * <http://www.apache.org/>.

  *

  */

 package ch.boye.httpclientandroidlib.impl.cookie;

 import java.lang.ref.SoftReference;

 import java.text.ParseException;

 import java.text.SimpleDateFormat;

 import java.util.Calendar;

 import java.util.Date;

 import java.util.HashMap;

 import java.util.Locale;

 import java.util.Map;

 import java.util.TimeZone;

 import ch.boye.httpclientandroidlib.annotation.Immutable;

 /**

  * A utility class for parsing and formatting HTTP dates as used in cookies and

  * other headers.  This class handles dates as defined by RFC 2616 section

  * 3.3.1 as well as some other common non-standard formats.

  *

  *

  * @since 4.0

  */

 @Immutable

 public final class DateUtils {

     /**

      * Date format pattern used to parse HTTP date headers in RFC 1123 format.

      */

     public static final String PATTERN_RFC1123 = "EEE, dd MMM yyyy HH:mm:ss zzz";

     /**

      * Date format pattern used to parse HTTP date headers in RFC 1036 format.

      */

     public static final String PATTERN_RFC1036 = "EEEE, dd-MMM-yy HH:mm:ss zzz";

     /**

      * Date format pattern used to parse HTTP date headers in ANSI C

      * <code>asctime()</code> format.

      */

     public static final String PATTERN_ASCTIME = "EEE MMM d HH:mm:ss yyyy";

     private static final String[] DEFAULT_PATTERNS = new String[] {

         PATTERN_RFC1036,

         PATTERN_RFC1123,

         PATTERN_ASCTIME

     };

     private static final Date DEFAULT_TWO_DIGIT_YEAR_START;

     public static final TimeZone GMT = TimeZone.getTimeZone("GMT");

     static {

         Calendar calendar = Calendar.getInstance();

         calendar.setTimeZone(GMT);

         calendar.set(2000, Calendar.JANUARY, 1, 0, 0, 0);

         calendar.set(Calendar.MILLISECOND, 0);

         DEFAULT_TWO_DIGIT_YEAR_START = calendar.getTime();

     }

     /**

      * Parses a date value.  The formats used for parsing the date value are retrieved from

      * the default http params.

      *

      * @param dateValue the date value to parse

      *

      * @return the parsed date

      *

      * @throws DateParseException if the value could not be parsed using any of the

      * supported date formats

      */

     public static Date parseDate(String dateValue) throws DateParseException {

         return parseDate(dateValue, null, null);

     }

     /**

      * Parses the date value using the given date formats.

      *

      * @param dateValue the date value to parse

      * @param dateFormats the date formats to use

      *

      * @return the parsed date

      *

      * @throws DateParseException if none of the dataFormats could parse the dateValue

      */

     public static Date parseDate(final String dateValue, String[] dateFormats)

         throws DateParseException {

         return parseDate(dateValue, dateFormats, null);

     }

     /**

      * Parses the date value using the given date formats.

      *

      * @param dateValue the date value to parse

      * @param dateFormats the date formats to use

      * @param startDate During parsing, two digit years will be placed in the range

      * <code>startDate</code> to <code>startDate + 100 years</code>. This value may

      * be <code>null</code>. When <code>null</code> is given as a parameter, year

      * <code>2000</code> will be used.

      *

      * @return the parsed date

      *

      * @throws DateParseException if none of the dataFormats could parse the dateValue

      */

     public static Date parseDate(

         String dateValue,

         String[] dateFormats,

         Date startDate

     ) throws DateParseException {

         if (dateValue == null) {

             throw new IllegalArgumentException("dateValue is null");

         }

         if (dateFormats == null) {

             dateFormats = DEFAULT_PATTERNS;

         }

         if (startDate == null) {

             startDate = DEFAULT_TWO_DIGIT_YEAR_START;

         }

         // trim single quotes around date if present

         // see issue #5279

         if (dateValue.length() > 1

             && dateValue.startsWith("'")

             && dateValue.endsWith("'")

         ) {

             dateValue = dateValue.substring (1, dateValue.length() - 1);

         }

         for (String dateFormat : dateFormats) {

             SimpleDateFormat dateParser = DateFormatHolder.formatFor(dateFormat);

             dateParser.set2DigitYearStart(startDate);

             try {

                 return dateParser.parse(dateValue);

             } catch (ParseException pe) {

                 // ignore this exception, we will try the next format

             }

         }

         // we were unable to parse the date

         throw new DateParseException("Unable to parse the date " + dateValue);

     }

     /**

      * Formats the given date according to the RFC 1123 pattern.

      *

      * @param date The date to format.

      * @return An RFC 1123 formatted date string.

      *

      * @see #PATTERN_RFC1123

      */

     public static String formatDate(Date date) {

         return formatDate(date, PATTERN_RFC1123);

     }

     /**

      * Formats the given date according to the specified pattern.  The pattern

      * must conform to that used by the {@link SimpleDateFormat simple date

      * format} class.

      *

      * @param date The date to format.

      * @param pattern The pattern to use for formatting the date.

      * @return A formatted date string.

      *

      * @throws IllegalArgumentException If the given date pattern is invalid.

      *

      * @see SimpleDateFormat

      */

     public static String formatDate(Date date, String pattern) {

         if (date == null) throw new IllegalArgumentException("date is null");

         if (pattern == null) throw new IllegalArgumentException("pattern is null");

         SimpleDateFormat formatter = DateFormatHolder.formatFor(pattern);

         return formatter.format(date);

     }

     /** This class should not be instantiated. */

     private DateUtils() {

     }

     /**

      * A factory for {@link SimpleDateFormat}s. The instances are stored in a

      * threadlocal way because SimpleDateFormat is not threadsafe as noted in

      * {@link SimpleDateFormat its javadoc}.

      *

      */

     final static class DateFormatHolder {

         private static final ThreadLocal<SoftReference<Map<String, SimpleDateFormat>>>

             THREADLOCAL_FORMATS = new ThreadLocal<SoftReference<Map<String, SimpleDateFormat>>>() {

             @Override

             protected SoftReference<Map<String, SimpleDateFormat>> initialValue() {

                 return new SoftReference<Map<String, SimpleDateFormat>>(

                         new HashMap<String, SimpleDateFormat>());

             }

         };

         /**

          * creates a {@link SimpleDateFormat} for the requested format string.

          *

          * @param pattern

          *            a non-<code>null</code> format String according to

          *            {@link SimpleDateFormat}. The format is not checked against

          *            <code>null</code> since all paths go through

          *            {@link DateUtils}.

          * @return the requested format. This simple dateformat should not be used

          *         to {@link SimpleDateFormat#applyPattern(String) apply} to a

          *         different pattern.

          */

         public static SimpleDateFormat formatFor(String pattern) {

             SoftReference<Map<String, SimpleDateFormat>> ref = THREADLOCAL_FORMATS.get();

             Map<String, SimpleDateFormat> formats = ref.get();

             if (formats == null) {

                 formats = new HashMap<String, SimpleDateFormat>();

                 THREADLOCAL_FORMATS.set(

                         new SoftReference<Map<String, SimpleDateFormat>>(formats));

             }

             SimpleDateFormat format = formats.get(pattern);

             if (format == null) {

                 format = new SimpleDateFormat(pattern, Locale.US);

                 format.setTimeZone(TimeZone.getTimeZone("GMT"));

                 formats.put(pattern, format);

             }

             return format;

         }

     }

 }