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# Copyright (c) Django Software Foundation and individual contributors.
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# All rights reserved.
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# 
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# Redistribution and use in source and binary forms, with or without modification,
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# are permitted provided that the following conditions are met:
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# 
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#     1. Redistributions of source code must retain the above copyright notice, 
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#        this list of conditions and the following disclaimer.
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#     
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#     2. Redistributions in binary form must reproduce the above copyright 
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#        notice, this list of conditions and the following disclaimer in the
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#        documentation and/or other materials provided with the distribution.
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# 
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#     3. Neither the name of Django nor the names of its contributors may be used
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#        to endorse or promote products derived from this software without
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#        specific prior written permission.
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# 
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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# DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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# ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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# ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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# SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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import re
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import datetime
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import calendar
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MONTHS = 'jan feb mar apr may jun jul aug sep oct nov dec'.split()
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__D = r'(?P<day>\d{2})'
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__D2 = r'(?P<day>[ \d]\d)'
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__M = r'(?P<mon>\w{3})'
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__Y = r'(?P<year>\d{4})'
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__Y2 = r'(?P<year>\d{2})'
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__T = r'(?P<hour>\d{2}):(?P<min>\d{2}):(?P<sec>\d{2})'
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RFC1123_DATE = re.compile(r'^\w{3}, %s %s %s %s GMT$' % (__D, __M, __Y, __T))
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RFC850_DATE = re.compile(r'^\w{6,9}, %s-%s-%s %s GMT$' % (__D, __M, __Y2, __T))
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ASCTIME_DATE = re.compile(r'^\w{3} %s %s %s %s$' % (__M, __D2, __T, __Y))
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def parse_http_date(date):
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    """
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    Parses a date format as specified by HTTP RFC2616 section 3.3.1.
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    The three formats allowed by the RFC are accepted, even if only the first
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    one is still in widespread use.
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    Returns an floating point number expressed in seconds since the epoch, in
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    UTC.
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    """
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    # emails.Util.parsedate does the job for RFC1123 dates; unfortunately
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    # RFC2616 makes it mandatory to support RFC850 dates too. So we roll
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    # our own RFC-compliant parsing.
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    for regex in RFC1123_DATE, RFC850_DATE, ASCTIME_DATE:
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        m = regex.match(date)
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        if m is not None:
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            break
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    else:
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        raise ValueError("%r is not in a valid HTTP date format" % date)
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    try:
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        year = int(m.group('year'))
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        if year < 100:
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            if year < 70:
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                year += 2000
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            else:
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                year += 1900
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        month = MONTHS.index(m.group('mon').lower()) + 1
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        day = int(m.group('day'))
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        hour = int(m.group('hour'))
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        min = int(m.group('min'))
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        sec = int(m.group('sec'))
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        result = datetime.datetime(year, month, day, hour, min, sec)
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        return calendar.timegm(result.utctimetuple())
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    except Exception:
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        raise ValueError("%r is not a valid date" % date)
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def parse_http_date_safe(date):
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    """
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    Same as parse_http_date, but returns None if the input is invalid.
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    """
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    try:
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        return parse_http_date(date)
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    except Exception:
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        pass