Re: High-speed Date Formatting


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Re: High-speed Date Formatting

by fullermd (Priest)

on Jul 12, 2013 at 07:20 UTC ( [id://1043893]=note: print w/replies, xml )

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in reply to *SOLVED* High-speed Date Formatting

If they're all the same format (or possibly a sufficiently small number of formats), you may be able to use strptime. If you can get something that just hits the C func, it may be quite fast (and even if it doesn't, being able to specify a format rather than call a DWIM interpretation function should be faster anyway).

I see a POSIX::strptime that seems like it may thunk straight through to libc's implementation. DateTime::Format::Strptime looks like a perl reimplementation, so may be slower (but probably more portable, if your system's strptime is broken).

Comment on Re: High-speed Date Formatting

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Re^2: High-speed Date Formatting
by rjt (Curate) on Jul 12, 2013 at 08:34 UTC

Great idea! In fact, I had the same one earlier in this thread at least six hours ago. :-) Here's the relevant sub by itself:

    use Inline C => q@
    int epoch_sec(char * date) {
        char *tz_str = date + 26;
        struct tm tm;
        int tz;

        if (  strlen(date) != 31                           ||
            strptime(date, "%a, %d %b %Y %T", &tm) == NULL ||
              sscanf(tz_str, "%d", &tz) != 1)
        {
            printf("Invalid date %s\n", date);
            return 0;
        }

        return timegm(&tm) - 
            (tz < 0 ? -1 : 1)*(abs(tz)/100*3600 + abs(tz)%100*60);
    }
    @;
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Performs about 25 times faster than str2time.

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