C# Streamreader - Break on {CR}{LF} only

Question

I am trying to count the number of rows in a text file (to compare to a control file) before performing a complex SSIS insert package.

Currently I am using a StreamReader and it is breaking a line with a {LF} embedded into a new line, whereas SSIS is using {CR}{LF} (correctly), so the counts are not tallying up.

Does anyone know an alternate method of doing this where I can count the number of lines in the file based on {CR}{LF} Line breaks only?

Thanks in advance

Answer 1

Iterate through the file and count number of CRLFs.

Pretty straightforward implementation:

public int CountLines(Stream stream, Encoding encoding)
{
    int cur, prev = -1, lines = 0;
    using (var sr = new StreamReader(stream, encoding, false, 4096, true))
    {
        while ((cur = sr.Read()) != -1)
        {
            if (prev == '\r' && cur == '\n')
                lines++;

            prev = cur;
        }
    }

    //Empty stream will result in 0 lines, any content would result in at least one line
    if (prev != -1)
        lines++;

    return lines;
}

Example usage:

using(var s = File.OpenRead(@"<your_file_path>"))
    Console.WriteLine("Found {0} lines", CountLines(s, Encoding.Default));

Actually it's a find substring in string task. More generic algorithms can be used.

Answer 2

Here is an extension-method that reads the lines with line-seperator {Cr}{Lf} only, and not {LF}. You could do a count on it.

var count=  new StreamReader(@"D:\Test.txt").ReadLinesCrLf().Count()

But could also use it for reading files, sometimes usefull since the normal StreamReader.ReadLine breaks on both {Cr}{Lf} and {LF}. Can be used on any TextReader and works streaming (file size is not an issue).

    public static IEnumerable<string> ReadLinesCrLf(this TextReader reader, int bufferSize = 4096)
    {
        StringBuilder lineBuffer = null;

        //read buffer            
        char[] buffer = new char[bufferSize];
        int charsRead;

        var previousIsLf = false;

        while ((charsRead = reader.Read(buffer, 0, bufferSize)) != 0)
        {
            int bufferIndex = 0;
            int writeIdx = 0;
            do
            {
                var currentChar = buffer[bufferIndex];
                switch (currentChar)
                {
                    case '\n':
                        if (previousIsLf)
                        {
                            if (lineBuffer == null)
                            {
                                //return from current buffer writeIdx could be higher than 0 when multiple rows are in the buffer                                            
                                yield return new string(buffer, writeIdx, bufferIndex - writeIdx - 1);
                                //shift write index to next character that will be read
                                writeIdx = bufferIndex + 1;
                            }
                            else
                            {
                                Debug.Assert(writeIdx == 0, $"Write index should be 0, when linebuffer != null");
                                lineBuffer.Append(buffer, writeIdx, bufferIndex - writeIdx);
                                Debug.Assert(lineBuffer.ToString().Last() == '\r',$"Last character in linebuffer should be a carriage return now");
                                lineBuffer.Length--;
                                //shift write index to next character that will be read
                                writeIdx = bufferIndex + 1;
                                yield return lineBuffer.ToString();
                                lineBuffer = null;
                            }
                        }

                        previousIsLf = false;
                        break;
                    case '\r':
                        previousIsLf = true;
                        break;
                    default:
                        previousIsLf = false;
                        break;

                }


                bufferIndex++;
            } while (bufferIndex < charsRead);
            if (writeIdx < bufferIndex)
            {
                if (lineBuffer == null) lineBuffer = new StringBuilder();
                lineBuffer.Append(buffer, writeIdx, bufferIndex - writeIdx);
            }
        }
        //return last row
        if (lineBuffer != null && lineBuffer.Length > 0) yield return lineBuffer.ToString();
    }