Normalize newlines in C#

Question

I have a data stream that may contain \r, \n, \r\n, \n\r or any combination of them. Is there a simple way to normalize the data to make all of them simply become \r\n pairs to make display more consistent?

So something that would yield this kind of translation table:

\r     --> \r\n
\n     --> \r\n
\n\n   --> \r\n\r\n
\n\r   --> \r\n
\r\n   --> \r\n
\r\n\n --> \r\n\r\n

Answer 1

A Regex would help.. could do something roughly like this..

(\r\n|\n\n|\n\r|\r|\n) replace with \r\n

This regex produced these results from the table posted (just testing left side) so a replace should normalize.

\r   => \r 
\n   => \n 
\n\n => \n\n 
\n\r => \n\r 
\r\n => \r\n 
\r\n => \r\n 
\n   => \n

Answer 2

You're thinking too complicated. Ignore every \r and turn every \n into an \r\n.

In Pseudo-C#:

char[] chunk = new char[X];
StringBuffer output = new StringBuffer();

buffer.Read(chunk);
foreach (char c in chunk)
{
   switch (c)
   {
      case '\r' : break; // ignore
      case '\n' : output.Append("\r\n");
      default   : output.Append(c);
   }
 }

EDIT: \r alone is no line-terminator so I doubt you really want to expand \r to \r\n.

Answer 3

I believe this will do what you need:

using System.Text.RegularExpressions;
// ...
string normalized = Regex.Replace(originalString, @"\r\n|\n\r|\n|\r", "\r\n");

I'm not 100% sure on the exact syntax, and I don't have a .Net compiler handy to check. I wrote it in perl, and converted it into (hopefully correct) C#. The only real trick is to match "\r\n" and "\n\r" first.

To apply it to an entire stream, just run in on chunks of input. (You could do this with a stream wrapper if you want.)

---

The original perl:

$str =~ s/\r\n|\n\r|\n|\r/\r\n/g;

The test results:

[bash$] ./test.pl
\r -> \r\n
\n -> \r\n
\n\n -> \r\n\r\n
\n\r -> \r\n
\r\n -> \r\n
\r\n\n -> \r\n\r\n

---

Update: Now converts \n\r to \r\n, though I wouldn't call that normalization.

Answer 4

I'm with Jamie Zawinski on RegEx:

"Some people, when confronted with a problem, think "I know, I’ll use regular expressions." Now they have two problems"

For those of us who prefer readability:

• Step 1

Replace \r\n by \n Replace \n\r by \n (if you really want this, some posters seem to think not) Replace \r by \n

• Step 2 Replace \n by Environment.NewLine or \r\n or whatever.

Answer 5

I agree Regex is the answer, however, everyone else fails to mention Unicode line separators. Those (and their variations with \n) should be included.