/BOFC/PartialFileRead.cs

using System;

using System.IO;

using System.Text;



namespace BOF

{

    public enum LinesPercentage

    {

        Lines = 0,

        Percentage

    }



    public enum ReadType

    {

        Start = 0,

        Middle,

        End

    }



    public class PartialFileRead

    {

        #region Fields and Properties



        public string FileName { get; set; }



        public FileInfo FileInfo { get; private set; }



        public ReadType ReadType { get; set; }



        public long Lines { get; set; }



        public long ReadChars { get; private set; }



        public string ReadLines { get; private set; }



        public LinesPercentage LinesOrPercentage { get; set; }



        public bool DoTabs { get; set; }



        public long StartLine { get; set; }



        public long EndLine { get; set; }



        public string LineTerminator

        {

            get { return GetLineTerminator(); }

        }



        public string HeaderLine { get; private set; }



        public bool HasHeader { get; private set; }



        public string FooterLine { get; private set; }



        public bool HasFooter { get; private set; }



        #endregion



        #region Events



        public event ReadFileProgressChangedEventHandler ReadProgress;

        public event FileReadEventHandler FileRead;



        #endregion



        #region Constructor



        public PartialFileRead()

        {

            FileName = string.Empty;

            ReadType = ReadType.Start;

            Lines = 10;

            ReadChars = 0;

            ReadLines = string.Empty;

            LinesOrPercentage = LinesPercentage.Lines;

            DoTabs = false;

            StartLine = 0;

            EndLine = 0;

        }



        #endregion



        public string ReadFile()

        {

            //reset variables

            ReadChars = 0;

            ReadLines = string.Empty;

            HasFooter = false;

            FooterLine = string.Empty;

            HasHeader = false;

            HeaderLine = string.Empty;



            switch (ReadType)

            {

                case ReadType.Start:

                    ReadFileStart();

                    break;



                case ReadType.Middle:

                    ReadFileMiddle();

                    break;



                case ReadType.End:

                    ReadFileEnd();

                    break;



                default:

                    break;

            }



            CheckForHeaderAndFooter();



            OnFileRead();



            return ReadLines;

        }



        /// <summary>

        /// Crude guesstimate at the existence of a header or footer record.

        /// Based if line length less half of normal line, or if 2/3rds are non-numeric

        /// </summary>

        private void CheckForHeaderAndFooter()

        {

            //checks for header/footer in *read* text, not much use

            //string[] lines = ReadLines.Split('\n');



            //if (lines[0].Length < lines[1].Length / 2)

            //    HasHeader = true;

            //else

            //    HasHeader = false;



            ////there's an blank line at the end we need to ignore

            //if (lines[lines.Length - 2].Length < lines[lines.Length - 3].Length / 2)

            //    HasFooter = true;

            //else

            //    HasFooter = false;





            //header check, read first 2 lines

            using (StreamReader sr = FileInfo.OpenText())

            {

                string line1 = sr.ReadLine();

                string line2 = sr.ReadLine();



                if (line2 != null

                    && line1.Length < line2.Length / 2

                    || !(System.Text.RegularExpressions.Regex.Matches(line1, "[0-9]").Count > line1.Length / 3))

                {

                    HasHeader = true;

                    HeaderLine = line1;

                }

            }



            //footer check, read last 2 lines

            using (StreamReader sr = new StreamReader(FileInfo.FullName, true))

            {

                long len = sr.BaseStream.Length;

                int[] rb = new int[2];



                //skip trailing line terminators

                do

                {

                    len -= 2;

                    sr.BaseStream.Seek(len, SeekOrigin.Begin);

                    rb[1] = sr.BaseStream.ReadByte();

                    rb[0] = sr.BaseStream.ReadByte();

                } while (rb[0] == 10 && rb[1] == 13);



                //go back _lines lines

                int b = 0;

                for (int i = 0; i < 3 - 1; i++)

                {

                    do

                    {

                        len -= 1;

                        try

                        {

                            sr.BaseStream.Seek(len, SeekOrigin.Begin);

                            b = sr.BaseStream.ReadByte();

                        }

                        catch (IOException ex)

                        {

                            Console.WriteLine(ex.Message);



                            //more lines asked for than in file

                            //move to beginning

                            sr.BaseStream.Seek(0, SeekOrigin.Begin);

                        }

                    } while (b != 10 && len > 0);



                }



                string line1 = sr.ReadLine();

                string line2 = sr.ReadLine();



                if (line2.Length < line1.Length / 2 ||

                    !(System.Text.RegularExpressions.Regex.Matches(line1, "[0-9]").Count > line1.Length / 3))

                {

                    HasFooter = true;

                    FooterLine = line2;

                }

            }

        }



        private string GetLineTerminator()

        {

            FileInfo = new FileInfo(FileName);



            if (!FileInfo.Exists)

                throw new ApplicationException(FileInfo.Name + " not found!");



            byte[] b = new byte[2];



            //open file stream

            using (FileStream fs = FileInfo.Open(FileMode.Open, FileAccess.Read))

            {

                //read 2 bytes from end of file into b

                fs.Seek(-2, SeekOrigin.End);

                fs.Read(b, 0, 2);

            }



            return b[0].ToString() + ", " + b[1].ToString();

        }



        private void ReadFileStart()

        {

            FileInfo = new FileInfo(FileName);



            if (!FileInfo.Exists)

                throw new ApplicationException(FileInfo.Name + " not found!");



            long i = 0;

            string line;

            StringBuilder sb = new StringBuilder();



            using (StreamReader sr = FileInfo.OpenText())

            {

                switch (LinesOrPercentage)

                {

                    case LinesPercentage.Lines:

                        while ((i < Lines) && !sr.EndOfStream)

                        {

                            line = sr.ReadLine();

                            ReadChars += line.Length;



                            if (DoTabs)

                                line = line.Replace(',', '\t');



                            sb.AppendLine(line);



                            i++;

                            OnReadFileProgress(i, Lines);

                        }

                        break;



                    case LinesPercentage.Percentage:

                        double percent = FileInfo.Length * (Lines / 100);



                        while (ReadChars <= percent && !sr.EndOfStream)

                        {

                            line = sr.ReadLine();

                            ReadChars += line.Length;



                            if (DoTabs)

                                line = line.Replace(',', '\t');



                            sb.AppendLine(line);



                            i++;

                            OnReadFileProgress(ReadChars, (long) percent);

                        }

                        break;

                }

            }



            ReadLines = sb.ToString();

        }



        private void ReadFileMiddle()

        {

            FileInfo = new FileInfo(FileName);



            if (!FileInfo.Exists)

                throw new ApplicationException(FileInfo.Name + " not found!");



            if (StartLine <= 0)

                StartLine = 1;



            if (EndLine <= StartLine)

                EndLine = StartLine + 1;



            string line;

            long i = 0;

            StringBuilder sb = new StringBuilder();



            using (StreamReader sr = FileInfo.OpenText())

            {

                //skip the first lines

                while (i < (StartLine - 1) && !sr.EndOfStream)

                {

                    sr.ReadLine();

                    i++;

                    OnReadFileProgress(i, StartLine);

                }



                while (i < EndLine && !sr.EndOfStream)

                {

                    line = sr.ReadLine();



                    ReadChars += line.Length;



                    if (DoTabs)

                        line = line.Replace(',', '\t');



                    sb.AppendLine(line);



                    i++;

                    OnReadFileProgress(i, EndLine);

                }

            }



            ReadLines = sb.ToString();

        }



        private void ReadFileEnd()

        {

            FileInfo = new FileInfo(FileName);



            if (!FileInfo.Exists)

                throw new ApplicationException(FileInfo.Name + " not found!");



            StringBuilder sb = new StringBuilder();



            using (StreamReader sr = new StreamReader(FileInfo.FullName, true))

            {

                long len = sr.BaseStream.Length;

                int[] rb = new int[2];



                //skip trailing line terminators

                do

                {

                    len -= 2;

                    sr.BaseStream.Seek(len, SeekOrigin.Begin);

                    rb[1] = sr.BaseStream.ReadByte();

                    rb[0] = sr.BaseStream.ReadByte();

                } while (rb[0] == 10 && rb[1] == 13);



                //go back _lines lines

                int b = 0;

                for (int i = 0; i < Lines - 1; i++)

                {

                    do

                    {

                        len -= 1;

                        try

                        {

                            sr.BaseStream.Seek(len, SeekOrigin.Begin);

                            b = sr.BaseStream.ReadByte();

                        }

                        catch (IOException ex)

                        {

                            Console.WriteLine(ex.Message);



                            //more lines asked for than in file

                            //move to beginning

                            sr.BaseStream.Seek(0, SeekOrigin.Begin);

                        }

                    } while (b != 10 && len > 0);



                    OnReadFileProgress(i, Lines);

                }



                string line = string.Empty;

                do

                {

                    line = sr.ReadLine();



                    if (DoTabs)

                        line = line.Replace(',', '\t');



                    sb.AppendLine(line);

                } while (!String.IsNullOrEmpty(line) && !sr.EndOfStream);

            }



            ReadLines = sb.ToString();

        }



        #region Event Firers



        private void OnReadFileProgress(long progress, long total)

        {

            // if we have subscribers...fire

            if (ReadProgress != null)

            {

                int perc;



                if (total == 0)

                    total = 1;



                if (progress > total)

                    perc = 100;

                else

                    perc = (int) ((decimal) progress / total * 100);



                ReadProgress(this, new ReadProgressEventArgs(perc));

            }

        }



        private void OnFileRead()

        {

            // if we have subscribers...fire

            if (FileRead != null)

                FileRead(this, new EventArgs());

        }



        #endregion

    }



    public delegate void FileReadEventHandler(object sender, EventArgs e);



    public delegate void ReadFileProgressChangedEventHandler(object sender, ReadProgressEventArgs e);



    public class ReadProgressEventArgs : EventArgs

    {

        public int Percentage;



        public ReadProgressEventArgs(int percentage)

        {

            this.Percentage = percentage;

        }

    }



}