Question

In my binary to text decoding application (.NET 2.0) I found that the line:

logEntryTime.ToString("dd.MM.yy HH:mm:ss:fff")

takes 33% of total processing time. Does anyone have any ideas on how to make it faster?

EDIT: This app is used to process some binary logs and it currently takes 15 hours to run. So 1/3 of this will be 5 hours.

EDIT: I am using NProf for profiling. App is processing around 17 GBytes of binary logs.

Answer 1

It’s unfortunate that .NET doesn’t have a sort of "formatter" type which can parse a pattern and remember it.

If you’re always using the same format, you might want to hand-craft a formatter to do exactly that. Something along the lines of:

public static string FormatDateTime(DateTime dt)
{
    // Note: there are more efficient approaches using Span<char> these days.
    char[] chars = new char[21];
    Write2Chars(chars, 0, dt.Day);
    chars[2] = '.';
    Write2Chars(chars, 3, dt.Month);
    chars[5] = '.';
    Write2Chars(chars, 6, dt.Year % 100);
    chars[8] = ' ';
    Write2Chars(chars, 9, dt.Hour);
    chars[11] = ' ';
    Write2Chars(chars, 12, dt.Minute);
    chars[14] = ' ';
    Write2Chars(chars, 15, dt.Second);
    chars[17] = ' ';
    Write2Chars(chars, 18, dt.Millisecond / 10);
    chars[20] = Digit(dt.Millisecond % 10);
    
    return new string(chars);
}

private static void Write2Chars(char[] chars, int offset, int value)
{
    chars[offset] = Digit(value / 10);
    chars[offset+1] = Digit(value % 10);
}

private static char Digit(int value)
{
    return (char) (value + '0');
}

This is pretty ugly, but it’s probably a lot more efficient… benchmark it, of course!