LineReader.cs

LineReader.cs

/// <summary>
/// A stream reader which will puts the seek position to the right place after each line read.
/// </summary>
internal class LineReader
{
    private Stream stream;
    private Encoding encoding;

    /// <summary>
    /// Creates a new instance of this class.
    /// </summary>
    /// <param name="s">The stream.</param>
    /// <param name="encoding">The encoding.</param>
    public LineReader(Stream s, Encoding encoding)
    {
        this.stream = s;
        this.encoding = encoding;
    }

    /// <summary>
    /// Read a line from the file.
    /// </summary>
    /// <returns>The line, or null.</returns>
    public string ReadLine()
    {
        List<byte> bytes = new List<byte>();
        int totalBytesUsed = 0;
        long totalBytesRead = 0;

        bool lineStarted = false;
        bool lineEnded = false;

        while (true)
        {
            byte[] buffer = new byte[1024];
            int bytesRead = this.stream.Read(buffer, 0, 1024);
            totalBytesRead += bytesRead;

            if (bytesRead == 0)
            {
                break;
            }
            
            // go through each byte read
            for (int i = 0; i < bytesRead; i++)
            {
                if (buffer[i] == '\r' || buffer[i] == '\n')
                {
                    if (lineStarted)
                    {
                        // this is the second time we see these characters
                        lineEnded = true;
                    }
                }
                else
                {
                    lineStarted = true;

                    if (lineEnded)
                    {
                        // we ended the last line, read the first character of the next line
                        break;
                    }

                    bytes.Add(buffer[i]);
                }

                totalBytesUsed++;
            }

            if (lineEnded)
            {
                // found the end of a line                    
                break;
            }
        }

        // move the seek position back to the end of the line
        this.stream.Seek(totalBytesUsed - totalBytesRead, SeekOrigin.Current);

        return this.encoding.GetString(bytes.ToArray());
    }
}