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/***************************************************************************
* Rfc822DateTime.cs
*
* Copyright (C) 2006 Michael C. Urbanski
* Written by Mike Urbanski <michael.c.urbanski@gmail.com>
****************************************************************************/
/* THIS FILE IS LICENSED UNDER THE MIT LICENSE AS OUTLINED IMMEDIATELY BELOW:
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/
using System;
using System.Text.RegularExpressions;
namespace Migo.Syndication
{
public static class Rfc822DateTime
{
private const string monthsStr =
"Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec|" +
"January|February|March|April|May|June|July|August|" +
"September|October|November|December";
private const string daysOfWeek =
"Mon|Tue|Wed|Thu|Fri|Sat|Sun|" +
"Monday|Tuesday|Wednesday|Thursday|Friday|Saturday|Sunday";
private const string rfc822DTExp =
@"^(?<dayofweek>(" + daysOfWeek + "), )?" +
@"(?<day>\d\d?) " +
@"(?<month>" + monthsStr + ") " +
@"(?<year>\d\d(\d\d)?) " +
@"(?<hours>[0-2]?\d):(?<minutes>[0-5]\d)(:(?<seconds>[0-5]\d))?" +
@"( (?<timezone>[A-I]|[K-Z]|GMT|UT|EST|EDT|CST|CDT|MST|MDT|PST|PDT|([+-]\d\d\d\d))$)?";
private static readonly string[] months;
private static readonly Regex rfc822DTRegex;
static Rfc822DateTime()
{
months = monthsStr.Split ('|');
rfc822DTRegex = new Regex (rfc822DTExp,
RegexOptions.Compiled | RegexOptions.IgnoreCase);
}
public static DateTime Parse (string dateTime)
{
if (dateTime == null) {
throw new ArgumentNullException ("dateTime");
}
Match m = rfc822DTRegex.Match (dateTime);
if (m.Success) {
GroupCollection groups = m.Groups;
DateTime ret;
int day = Convert.ToInt32 (groups ["day"].Value);
int month = MonthToInt32 (groups ["month"].Value);
int year = Convert.ToInt32 (groups ["year"].Value);
int hours = Convert.ToInt32 (groups ["hours"].Value);
int minutes = Convert.ToInt32 (groups ["minutes"].Value);
int seconds = 0;
string secondsStr = groups ["seconds"].Value;
string timeZone = groups ["timezone"].Value;
if (secondsStr != String.Empty) {
seconds = Convert.ToInt32 (secondsStr);
}
if (year < 100) {
int curYear = DateTime.Now.Year;
year = curYear - (curYear % 100) + year;
}
ret = new DateTime (year, month, day, hours, minutes, seconds);
if (timeZone != String.Empty) {
ret -= ParseGmtOffset (timeZone);
}
return ret.ToLocalTime ();
}
throw new FormatException ("'dateTime' does not represent a valid RFC 822 date-time");
}
public static bool TryParse (string dateTime, out DateTime result)
{
bool ret = false;
result = DateTime.MinValue;
try {
result = Parse (dateTime);
ret = true;
} catch {}
return ret;
}
private static int MonthToInt32 (string month)
{
int i = 1;
foreach (string s in months) {
if (month == s) {
break;
}
if (++i % 13 == 0) {
i = 1;
}
}
return i;
}
private static TimeSpan ParseGmtOffset (string offset)
{
int offsetHours = 0;
int offsetMinutes = 0;
if (offset.Length == 5) {
offsetHours = Convert.ToInt32 (offset.Substring (1,2));
offsetMinutes = Convert.ToInt32 (offset.Substring (3,2));
if (offset [0] == '-') {
offsetHours *= -1;
offsetMinutes *= -1;
}
} else {
switch (offset)
{
case "GMT": case "UT": break;
case "EDT": offsetHours = -4; break;
case "EST": case "CDT": offsetHours = -5; break;
case "CST": case "MDT": offsetHours = -6; break;
case "MST": case "PDT": offsetHours = -7; break;
case "PST": offsetHours = -8; break;
case "Z": offsetHours = 0; break;
case "A": offsetHours = -1; break;
case "B": offsetHours = -2; break;
case "C": offsetHours = -3; break;
case "D": offsetHours = -4; break;
case "E": offsetHours = -5; break;
case "F": offsetHours = -6; break;
case "G": offsetHours = -7; break;
case "H": offsetHours = -8; break;
case "I": offsetHours = -9; break;
// Q. Why was 'J' left out of Z-Time?
// A. http://www.maybeck.com/ztime/
// That's what I like about this job, you learn stuff.
case "K": offsetHours = -10; break;
case "L": offsetHours = -11; break;
case "M": offsetHours = -12; break;
case "N": offsetHours = 1; break;
case "O": offsetHours = 2; break;
case "P": offsetHours = 3; break;
case "Q": offsetHours = 4; break;
case "R": offsetHours = 5; break;
case "S": offsetHours = 6; break;
case "T": offsetHours = 7; break;
case "U": offsetHours = 8; break;
case "V": offsetHours = 9; break;
case "W": offsetHours = 10; break;
case "X": offsetHours = 11; break;
case "Y": offsetHours = 12; break;
}
}
return TimeSpan.FromTicks (
(offsetHours * TimeSpan.TicksPerHour) +
(offsetMinutes * TimeSpan.TicksPerMinute)
);
}
}
}
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