.net Split by length

Question

I have a string value that its length is 5000 + characters long , i want to split this into 76 characters long with a new line at the end of each 76 characters. how woudld i do this in c#?

Answer 1

string[] FixedSplit(string s, int len)
{
   List<string> output;
   while (s.Length > len)
   {
      output.Add(s.Substring(0, len) + "\n");
      s.Remove(0, len);
   }
   output.Add(s + "\n");
   return output.ToArray();
}

Answer 2

A little uglier ... but much faster ;) (this version took 161 ticks... Aric's took 413)

I posted my test code on my blog. http://hackersbasement.com/?p=134 (I also found StringBuilder to be much slower than string.Join)

http://hackersbasement.com/?p=139 <= updated results

    string chopMe = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

    Stopwatch sw = new Stopwatch();

    sw.Start();
    char[] chopMeArray = chopMe.ToCharArray();
    int totalLength = chopMe.Length;
    int partLength = 12;
    int partCount = (totalLength / partLength) + ((totalLength % partLength == 0) ? 0 : 1);
    int posIndex = 0;
    char[] part = new char[partLength];
    string[] parts = new string[partCount];
    int get = partLength;
    for (int i = 0; i < partCount; i++)
    {
        get = Math.Min(partLength, totalLength - posIndex);
        Array.Copy(chopMeArray, posIndex, part, 0, get);
        parts[i] = new string(part, 0, get);
        posIndex += partLength;
    }

    var output = string.Join("\r\n", parts) + "\r\n";
    sw.Stop();
    Console.WriteLine(sw.ElapsedTicks);

Answer 3

public static string InsertNewLine(string s, int len)
{
 StringBuilder sb = new StringBuilder(s.Length + (int)(s.Length/len) + 1);
 int start = 0;
 for (start=0; start<s.Length-len; start+=len)
 {
  sb.Append(s.Substring(start, len));
  sb.Append(Environment.NewLine);
 }
 sb.Append(s.Substring(start));
 return sb.ToString();
}

where s would be your input string and len the desired line length (76).

Answer 4

public static IEnumerable<string> SplitString(string s, int length)
{
    var buf = new char[length];
    using (var rdr = new StringReader(s))
    {
        int l;
        l = rdr.ReadBlock(buf, 0, length);
        while (l > 0)
        {
            yield return (new string(buf, 0, l)) + Environment.NewLine;
            l = rdr.ReadBlock(buf, 0, length);
        }
    }
}

Then to put them back together:

string theString = GetLongString();
StringBuilder buf = new StringBuilder(theString.Length + theString.Length/76);
foreach (string s in SplitString(theString, 76) { buf.Append(s); }
string result = buf.ToString();

Or you could do this:

string InsertNewLines(string s, int interval)
{
    char[] buf = new char[s.Length + (int)Math.Ceiling(s.Length / (double)interval)];

    using (var rdr = new StringReader(s))
    {
        for (int i=0; i<buf.Length-interval; i++)
        {
            rdr.ReadBlock(buf, i, interval);
            i+=interval;
            buf[i] = '\n';
        }
        if (i < s.Length)
        {
            rdr.ReadBlock(buf, i, s.Length - i);
            buf[buf.Length - 1] = '\n';
        }
    }
    return new string(buf);
}

Answer 5

Try this:

s = Regex.Replace(s, @"(?<=\G.{76})", "\r\n");

EDIT: Apparently, this is the slowest method of all those posted so far. I wonder how it does if you pre-compile the regex:

Regex rx0 = new Regex(@"(?<=\G.{76})");

s = rx0.Replace(s, "\r\n"); // only time this portion

Also, how does it compare to a straight matching approach?

Regex rx1 = new Regex(".{76}");

s = rx1.Replace(s, "$0\r\n"); // only time this portion

I've always wondered how expensive those unbounded lookbehinds are.

Answer 6

In the end, this would be what I would use, I think

    static string fredou()
    {
        string s = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
        int partLength = 12;

        int stringLength = s.Length;
        StringBuilder n = new StringBuilder(stringLength + (int)(stringLength / partLength) + 1);
        int chopSize = 0;
        int pos = 0;

        while (pos < stringLength)
        {
            chopSize = (pos + partLength) < stringLength ? partLength : stringLength - pos;
            n.Append(s , pos, chopSize);
            n.Append("\r\n");
            pos += chopSize;
        }

        return n.ToString();         
    }

by looking at AppendLine under reflector:

    <ComVisible(False)> _
    Public Function AppendLine(ByVal value As String) As StringBuilder
        Me.Append(value)
        Return Me.Append(Environment.NewLine)
    End Function

    Public Shared ReadOnly Property NewLine As String
        Get
            Return ChrW(13) & ChrW(10)
        End Get
    End Property

For me, speed wise, doing it manually > AppendLine

Answer 7

One more.... (first time through slowish, subsequent runs, similar to the faster times posted above)

private void button1_Click(object sender, EventArgs e)
{
  string chopMe = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
  Stopwatch sw = new Stopwatch();
  sw.Start();
  string result = string.Join("\r\n", ChopString(chopMe).ToArray());
  sw.Stop();
  MessageBox.Show(result + " " + sw.ToString());
}


public IEnumerable<string> ChopString(string s)
{
  int i = 0;
  while (i < s.Length)
  {
    yield return i + PARTLENGTH <= s.Length ? s.Substring(i,PARTLENGTH) :s.Substring(i) ;
    i += PARTLENGTH;
  }
}

Edit: I was curious to see how fast substring was...

Answer 8

If you're writing Base64 data, try writing

Convert.ToBase64String(bytes, Base64FormattingOptions.InsertLineBreaks);

This will insert a newline every 76 characters

Answer 9

The string is 5000 characters... I don't think speed is really of the essence unless you're doing this thousands or maybe even millions of times, especially when the OP didn't even mention speed being important. Premature optimization?

I would probably use recursion as it will, in my opinion, lead to the simplest code.

This may not be syntatically correct, as I know .NET but not C#.

String ChunkString(String s, Integer chunkLength) {
    if (s.Length <= chunkLength) return s;
    return String.Concat(s.Substring(0, chunkLength), 
                         ChunkString(s.Substring(chunkLength)));
}

Answer 10

mostly for the fun of it, here's a different solution implemented as extension method to string: (\r\n used explicitly so will only support that format for newline);

public static string Split(this string str, int len)
        {
            char org = str.ToCharArray();
            int parts = str.Length / len + (str.Length % len == 0 ? 0 : 1);
            int stepSize = len + newline.Length;
            char[] result = new char[parts * stepSize];
            int resLen = result.Length;

            for (int i =0;i<resLen ;i+stepSize)
            {
                Array.Copy(org,i*len,result,i*stepSize);
                resLen[i++] = '\r';
                resLen[i++] = '\n';
            }
            return new string(result);
        }