DelimitedReader.cs

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;

namespace ByteTerrace
{
    public class DelimitedReader : IEnumerable<IEnumerable<string>>, IDisposable
    {
        private const char DEFAULT_ESCAPE_CHAR = '"';
        private const char DEFAULT_SEPARATOR_CHAR = ',';

        private readonly char m_escapeChar;
        private bool m_isDisposed;
        private readonly char m_separatorChar;
        private readonly TextReader m_textReader;

        public char EscapeChar {
            get {
                return m_escapeChar;
            }
        }
        public bool IsDisposed {
            get {
                return m_isDisposed;
            }
            private set {
                m_isDisposed = value;
            }
        }
        public char SeparatorChar {
            get {
                return m_separatorChar;
            }
        }
        public TextReader TextReader {
            get {
                return m_textReader;
            }
        }

        public DelimitedReader(TextReader textReader, char separatorChar = DEFAULT_SEPARATOR_CHAR, char escapeChar = DEFAULT_ESCAPE_CHAR) {
            m_escapeChar = escapeChar;
            m_separatorChar = separatorChar;
            m_textReader = textReader;
        }

        public void Dispose() {
            Dispose(true);
            GC.SuppressFinalize(this);
        }
        protected virtual void Dispose(bool disposing) {
            if (!IsDisposed) {
                if (disposing) {
                    TextReader.Dispose();
                }

                IsDisposed = true;
            }
        }
        public IEnumerator<IEnumerable<string>> GetEnumerator() {
            return ReadFields().GetEnumerator();
        }
        IEnumerator IEnumerable.GetEnumerator() {
            return GetEnumerator();
        }
        public IEnumerable<IEnumerable<string>> ReadFields() {
            return ReadFields(TextReader, SeparatorChar, EscapeChar);
        }

        public static DelimitedReader Create(TextReader textReader, char separatorChar = DEFAULT_SEPARATOR_CHAR, char escapeChar = DEFAULT_ESCAPE_CHAR) {
            return new DelimitedReader(textReader, separatorChar, escapeChar);
        }
        public static string ReadField(string input, int offset, int position, char escapeChar) {
            if (input[offset] == escapeChar) {
                if (position - offset != 2) {
                    return input.Substring(offset + 1, position - offset - 2);
                }
                else {
                    return string.Empty;
                }
            }
            else {
                return input.Substring(offset, position - offset);
            }
        }
        public static IEnumerable<IEnumerable<string>> ReadFields(TextReader reader, char separatorChar = DEFAULT_SEPARATOR_CHAR, char escapeChar = DEFAULT_ESCAPE_CHAR) {
            var charsToSeek = new char[] { escapeChar, separatorChar };
            var endOfLine = 0;
            var escaping = false;
            var fields = new List<string>();
            var line = string.Empty;
            var offset = 0;
            var position = -1;

            while ((line = reader.ReadLine()) != null) {
                endOfLine = line.Length;

                while (position < endOfLine) {
                    if (escaping) {
                        position = line.IndexOf(escapeChar, ++position);
                    }
                    else {
                        position = line.IndexOfAny(charsToSeek, ++position);
                    }

                    if (position != -1) {
                        if (line[position] == escapeChar) {
                            escaping = !escaping;

                            if ((((position - offset) > 2)) && (line[position - 1] == escapeChar)) {
                                line = line.Remove(position, 1);
                                endOfLine--;
                            }
                        }
                        else {
                            fields.Add(ReadField(line, offset, position, escapeChar));
                            offset = position + 1;
                        }
                    }
                    else {
                        break;
                    }
                }

                if (offset == line.Length) {
                    fields.Add(string.Empty);
                }
                else {
                    fields.Add(ReadField(line, offset, line.Length, escapeChar));
                }
            
                yield return fields;
                offset = 0;
                fields.Clear();
            }
        }
    }
}