current community

your communities

more stack exchange communities

Stack Exchange
tour help
careers 2.0
Take the 2-minute tour ×
Stack Overflow is a question and answer site for professional and enthusiast programmers. It's 100% free, no registration required.
up vote 1 down vote favorite

following a recent thread in stackoverflow, I'm posting a new question: I have several strings from which I want to extract the encoding type. I'm willing to do it using regex:

Examples:

utf-8 quoted printable
string str = "=?utf-8?Q?=48=69=67=68=2d=45=6e=64=2d=44=65=73=69=67=6e=65=72=2d=57=61=74=63=68=2d=52=65=70=6c=69=63=61=73=2d=53=61=76=65=2d=54=48=4f=55=53=41=4e=44=53=2d=32=30=31=32=2d=4d=6f=64=65=6c=73?=";

utf-8 Base 64
string fld4 = "=?utf-8?B?VmFsw6lyaWUgTWVqc25lcm93c2tp?= <[email protected]>";

Windows 1258 Base 64
 string msg2= "=?windows-1258?B?UkU6IFRyIDogUGxhbiBkZSBjb250aW51aXTpIGQnYWN0aXZpdOkgZGVz?= =?windows-1258?B?IHNlcnZldXJzIFdlYiBHb1ZveWFnZXN=?=";

iso-8859-1 Quoted printable 
string fld2 = "=?iso-8859-1?Q?Fr=E9d=E9ric_Germain?= <[email protected]>";

etc...

In order to write a generic decoding function, we need to extract:

  • the charset (utf-8, Windows1258, etc...)

  • the transfert encoding type (quoted printable or base 64)

  • the encoded string

Any idea how to extract the pattern between ?xxx?Q? or ?xxx?B?

Note: this can be uppercase or lowercase

Thanks.

share|improve this question
2  
Yes, that's a very simple regex. At which point are you stuck? –  dtb Jul 10 '13 at 20:33
2  
string.Split can also work for something so simple. –  Jon Jul 10 '13 at 20:35
    
@Jon, +1 for realizing the simplest way to get the job done. –  Michael Perrenoud Jul 10 '13 at 20:36
    
this does not return separately the 3 informations and does not deal with multiple patterns (see example 3). –  CloudAnywhere Jul 10 '13 at 20:50
    
@CloudAnywhere See my updated regex answer here (the last piece of code) which extracts it from the previous step. –  Jerry Jul 10 '13 at 21:07
show 1 more comment

2 Answers

up vote 1 down vote

Here is a Rubular that will do it for you. In short, this Regex =\?(.*?)\?[QBqb] will grab that encoding. But one thing to note is this, when grabbing the results, the third example you gave has two matches in it so just make sure you decide what you want to do with the second match.

share|improve this answer
    
You hitted the difficult point. I probably have to return a list of classes, something like that:List<Encoded> list; public class Encoded { string _Charset; string _ContentTransfertEncoding; string _Data; } –  CloudAnywhere Jul 10 '13 at 20:47
    
... and perform a set of operation: 1. Get the 2 strings for example 3, and for each string get the charset,the encoding and the content. –  CloudAnywhere Jul 10 '13 at 20:49
add comment
up vote -1 down vote

Here is a full working solution

public class Encoded
    {
        public string Charset;
        public string ContentTransfertEncoding;
        public string Data;
    }

    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Text;
    using System.Text.RegularExpressions;

    namespace ConsoleApplication2
    {
     public class Decoding
{

    public Decoding()
    {

    }

    public List<Encoded> Process(string data)
    {
        List<Encoded> list = new List<Encoded>();

        var occurences = new Regex(@"=\?[a-zA-Z0-9?=-]*\?[BbQq]\?[a-zA-Z0-9?=-]*\?=", RegexOptions.IgnoreCase);
        var matches = occurences.Matches(data);
        foreach (Match match in matches)
        {
            Encoded cls = new Encoded();
            cls.Data = match.Groups[0].Value;
            cls.Charset = GetCharset(cls.Data);                
            cls.ContentTransfertEncoding = GetContentTransfertEncoding(cls.Data);

            // cleanup data
            int pos = cls.Data.IndexOf("=?");
            pos = cls.Data.IndexOf("?",pos+ 2);
            cls.Data = cls.Data.Substring(pos + 3);
            cls.Data = cls.Data.Replace("?=", "");                
            list.Add(cls);
        }
        return list;            
    }

    private string GetContentTransfertEncoding(string data)
    {
        var occurences = new Regex(@"=\?(.*?)\?[QBqb]", RegexOptions.IgnoreCase);
        var matches = occurences.Matches(data);

        foreach (Match match in matches)
        {
            int pos = match.Groups[0].Value.LastIndexOf('?');

            return match.Groups[0].Value.Substring(pos+1);

        }
        return data;
    }

    public string GetCharset(string data)
    {
        var occurences = new Regex(@"=\?(.*?)\?[QBqb]", RegexOptions.IgnoreCase);
        var matches = occurences.Matches(data);

        foreach (Match match in matches)
        {
            string str1 = match.Groups[0].Value.Replace("=?", "");
            int pos = str1.IndexOf('?');
            str1 = str1.Substring(0, pos);
            return str1; // there should be only 1 match
        }
        return data;
    }

    public string Decodeetc...()
   }
share|improve this answer
    
why is there a -1? this is the correct answer now in production without bugs since 6 months –  CloudAnywhere Feb 7 at 10:38
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.