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I have an application written in .NETMF that requires that I be able to parse an RFC822-Datetime.

Normally, this would be easy, but NETMF does not have a DateTime.parse() method, nor does it have some sort of a pattern matching implementation, so I'm pretty much stuck.

Any ideas?

EDIT: "Intelligent" solutions are probably needed. Part of the reason this is difficult is that the datetime in question has a tendency to have extra spaces in it (but only sometimes). A simple substring solution might work one day, but fail the next when the datetime has an extra space somewhere between the parts. I do not have control over the datetime, it is from the NOAA.

chris12892
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  • Interesting question. MF is notoriously slim, and 99.95% of an OSS you try will fail to compile. Genuinely interested in the replies to this. – Marc Gravell Jun 06 '10 at 20:13

1 Answers1

4

Good ol' string manipulation:

Sun, 06 Jun 2010 20:07:44 +0000
          1         2         3
0123456789012345678901234567890

string x = Sanitize("  Sun,  06 \t Jun 2010 \r\n 20:07:44 +0000  ");

int day    = int.Parse(x.Substring(5, 2));
int month  = Array.IndexOf(months, x.Substring(8, 3)) + 1;
int year   = int.Parse(x.Substring(12, 4));

int hour   = int.Parse(x.Substring(17, 2));
int minute = int.Parse(x.Substring(20, 2));
int second = int.Parse(x.Substring(23, 2));

int offsetSgn    = (x[26] == "-") ? -1 : 1;
int offsetHour   = int.Parse(x.Substring(27, 2));
int offsetMinute = int.Parse(x.Substring(29, 2));

DateTime result = new DateTime(year, month, day, hour, minute, second, 0);
TimeSpan offset = new TimeSpan(offsetHour, offsetMinute, 0);

// TODO: add offset...

with

string[] months = new string[12];
months[0] = "Jan";
months[1] = "Feb";
months[2] = "Mar";
months[3] = "Apr";
months[4] = "May";
months[5] = "Jun";
months[6] = "Jul";
months[7] = "Aug";
months[8] = "Sep";
months[9] = "Oct";
months[10] = "Nov";
months[11] = "Dec";

and

string Sanitize(string s)
{
    if (s == null)
    {
        return null;
    }

    char[] buffer = new char[s.Length];
    int pos = 0;
    bool inSpace = true;

    for (int i = 0; i < s.Length; i++)
    {
        if (s[i] == ' ' || s[i] == '\t' || s[i] == '\r' || s[i] == '\n')
        {
            if (!inSpace)
            {
                buffer[pos] = ' ';
                pos++;
                inSpace = true;
            }
        }
        else
        {
            buffer[pos] = s[i];
            pos++;
            inSpace = false;
        }
    }

    return new string(buffer, 0, pos);
}
dtb
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  • This is good, but one thing I forgot to mention is that the datetime that I am parsing has been known to sometimes have extra spaces in it (Don't ask. It's an NOAA XML METAR. I have no idea WTF). I had a solution in PHP that would intelligently go through and attempt to figure out what part each of the dt was. I guess if I can't do that, a solution like this is my only option, although I wish NETMF had even a simple pattern matching class. – chris12892 Jun 06 '10 at 20:20
  • Just zap all spaces with string.Replace(" ", "") – Hans Passant Jun 06 '10 at 20:24
  • The spaces are the only deliminator, so zapping them all isn't an option. That only makes the problem worse, maybe impossible without a proper pattern matching implementation. EDIT: Oh wait, I see your point. Yeah, that might also be an option. – chris12892 Jun 06 '10 at 20:32
  • You may want to add some error checking to make sure the sanitized string is indeed in the right format. Also, don't forget to adjust `result` for the timezone offset. Look at the spec if my code really covers all valid inputs or if, for example, `+0000` can also be expressed as `UTC` or `GMT`. – dtb Jun 06 '10 at 20:53
  • In this case, I do know that the string will always be expressed in the +0000 format. I am definitely going to extend this, but all I needed was a sharp prod in the right direction, which your post definitely gave me :) Thanks again. – chris12892 Jun 06 '10 at 21:02
  • I think the answer here is much simpler: http://stackoverflow.com/questions/284775/how-do-i-parse-and-convert-datetime-s-to-the-rfc-822-date-time-format – DermFrench Jun 04 '15 at 10:01