Split a string into sub strings by fixed width

Question

I've got data which looks like this...

   1 TESTAAA      SERNUM    A DESCRIPTION
   2 TESTBBB      ANOTHR    ANOTHER DESCRIPTION
   3 TESTXXX      BLAHBL

My question is, what is the most efficient way to split this data into it's smaller substrings, as there will be hundreds of lines. Also, some of the lines will be missing the last column. I tried to do regex but wasn't successful with the pattern I used for widths. The data above should break down into these fields (length of each column listed below)

{id} {firsttext} {serialhere} {description}
 4    22          6            30+

Can anyone lend a hand or suggest a good regex matching pattern to extract the information?

Thanks, Simon

Answer 1

Try the following regex:

(.{4})(.{22})(.{6})(.+)?

If the values are always nonempty and separated with whitespace (that is, they don't run into each other), then try something simpler like

line.Split(" ")

Answer 2

I would actually recommend writing a method to do this via String.Substring directly. This will likely be more efficient at giving you the exact required widths.

This would likely work (though it's untested, and purposefully does not strip the string padding):

public static string[] SplitFixedWidth(string original, bool spaceBetweenItems, params int[] widths)
{
    string[] results = new string[widths.Length];
    int current = 0;

    for (int i = 0; i < widths.Length; ++i)
    {
        if (current < original.Length)
        {
            int len = Math.Min(original.Length - current, widths[i]);
            results[i] = original.Substring(current, len);
            current += widths[i] + (spaceBetweenItems ? 1 : 0);
        }
        else results[i] = string.Empty;
    }

    return results;
}

That being said, if you're reading this from a Stream or text file directly, using TextFieldParser will allow you to read the data directly as fixed width data.