QuotedCoding.cs :  » Bloggers » dasBlog » Lesnikowski » Pawel » Mail » Pop3 » C# / CSharp Open Source

using System;
using System.Text;
using System.Text.RegularExpressions;

namespace Lesnikowski.Pawel.Mail.Pop3{
  /// <summary>
  /// Summary description for Coding.
  /// </summary>
  public abstract class QuotedCoding
  {
    /// <summary>
    /// zwraca tablice bajtow
    /// zamienia 3 znaki np '=A9' na odp wartosc.
    /// zamienia '_' na znak 32
    /// </summary>
    /// <param name="s">Kupis_Pawe=B3</param>
    /// <returns>Kupis Pawe</returns>
    public static byte[] GetByteArray(string s)
    {
            // clemensv -- added check
      if ( s == null || s.Length == 0 )
                return new byte[0];
            
            byte[] buffer=new byte[s.Length];


      int bufferPosition=0;
      for(int i=0;i<s.Length;i++)
      {
                if (s[i]=='=' )
                {
                    if ( i<(s.Length-2) )
                    {
                        if ( s[i+1]=='\r' && s[i+2]=='\n')
                        {
                            bufferPosition--;
                        }
                        else
                        {
                            buffer[bufferPosition]=System.Convert.ToByte(s.Substring(i+1,2),16);
                        }
                        i+=2;
                    }
                    else
                    {
                        break;
                    }
                }
                else if (s[i]=='_')
                {
                    buffer[bufferPosition]=32;
                }
                else
                {
                    buffer[bufferPosition]=(byte)s[i];
                }
        bufferPosition++;
      }
      byte[] newArray=new byte[bufferPosition];
      Array.Copy(buffer,newArray,bufferPosition);
      return newArray;
    }

    /// <summary>
    /// Decoduje string "=?iso-8859-2?Q?Kupis_Pawe=B3?=" 
    /// lub zakodowany base64
    /// na poprawny
    /// </summary>
    /// <param name="s">"=?iso-8859-2?Q?Kupis_Pawe=B3?="</param>
    /// <returns>Kupis Pawe</returns>
    public static string DecodeOne(string charset, string cmd, string subject )
    {
            byte[] bArray;

      if (cmd=="Q") //querystring
            {
                bArray=GetByteArray(subject);
            }
            else if (cmd=="B")//base64
            {
                bArray=Convert.FromBase64String(subject);
            }
            else
            {
                return subject;
            }
      Encoding encoding=Encoding.GetEncoding(charset); 
      return encoding.GetString(bArray);
    }

    private static readonly Regex splitterRegex = new Regex(@"(?<unencoded>((?!=\?).)*)?(?:=\?(?<charset>.*?)\?(?<cmd>\w)\?(?<subject>.*?)\?=)?",RegexOptions.Compiled);
    /// <summary>
    /// decoduje string zamienia wpisy (=?...?=) na odp wartosci
    /// </summary>
    /// <param name="s">"ala i =?iso-8859-2?Q?Kupis_Pawe=B3?= ma kota"</param>
    /// <returns>"ala i Pawe Kupis ma kota"</returns>
    public static string Decode(string s)
    {
      StringBuilder retString=new StringBuilder();
            foreach( Match m in splitterRegex.Matches(s) )
            {
                if ( m.Groups["unencoded"].Success )
                {
                     retString.Append(m.Groups["unencoded"].Value);
                }
                if ( m.Groups["charset"].Success && m.Groups["cmd"].Success && m.Groups["subject"].Success )
                {
                     retString.Append(DecodeOne(m.Groups["charset"].Value,m.Groups["cmd"].Value,m.Groups["subject"].Value));
                }
            }
            return retString.ToString();
    }

  }
}