/// <summary>
/// Decodes a Quoted-Printable string according to <a href="http://tools.ietf.org/html/rfc2047">RFC 2047</a>.<br />
/// RFC 2047 is used for decoding Encoded-Word encoded strings.
/// </summary>
/// <param name="toDecode">Quoted-Printable encoded string</param>
/// <param name="encoding">Specifies which encoding the returned string will be in</param>
/// <returns>A decoded string in the correct encoding</returns>
/// <exception cref="T:System.ArgumentNullException">If <paramref name="toDecode" /> or <paramref name="encoding" /> is <see langword="null" /></exception>
public static string DecodeEncodedWord(string toDecode, Encoding encoding)
{
if (toDecode == null)
{
throw new ArgumentNullException("toDecode");
}
if (encoding == null)
{
throw new ArgumentNullException("encoding");
}
return(encoding.GetString(QuotedPrintable.Rfc2047QuotedPrintableDecode(toDecode, true)));
}
public static string Decode(string encodedWords)
{
if (encodedWords == null)
{
throw new ArgumentNullException("encodedWords");
}
const string encodedWordRegex = @"\=\?(?<Charset>\S+?)\?(?<Encoding>\w)\?(?<Content>.+?)\?\=";
const string replaceRegex = @"(?<first>" + encodedWordRegex + @")\s+(?<second>" + encodedWordRegex + ")";
encodedWords = Regex.Replace(encodedWords, replaceRegex, "${first}${second}");
encodedWords = Regex.Replace(encodedWords, replaceRegex, "${first}${second}");
string decodedWords = encodedWords;
MatchCollection matches = Regex.Matches(encodedWords, encodedWordRegex);
foreach (Match match in matches)
{
if (!match.Success)
{
continue;
}
string fullMatchValue = match.Value;
string encodedText = match.Groups["Content"].Value;
string encoding = match.Groups["Encoding"].Value;
string charset = match.Groups["Charset"].Value;
Encoding charsetEncoding = EncodingFinder.FindEncoding(charset);
string decodedText;
switch (encoding.ToUpperInvariant())
{
case "B":
decodedText = Base64Decode(encodedText, charsetEncoding);
break;
case "Q":
decodedText = QuotedPrintable.DecodeEncodedWord(encodedText, charsetEncoding);
break;
default:
throw new ArgumentException("The encoding " + encoding + " was not recognized");
}
decodedWords = decodedWords.Replace(fullMatchValue, decodedText);
}
return(decodedWords);
}
/// <summary>
/// This is the actual decoder.
/// </summary>
/// <param name="toDecode">The string to be decoded from Quoted-Printable</param>
/// <param name="encodedWordVariant">
/// If <see langword="true" />, specifies that RFC 2047 quoted printable decoding is used.<br />
/// This is for quoted-printable encoded words<br />
/// <br />
/// If <see langword="false" />, specifies that RFC 2045 quoted printable decoding is used.<br />
/// This is for quoted-printable Content-Transfer-Encoding
/// </param>
/// <returns>A decoded byte array that was described by <paramref name="toDecode" /></returns>
/// <exception cref="T:System.ArgumentNullException">If <paramref name="toDecode" /> is <see langword="null" /></exception>
/// <remarks>See <a href="http://tools.ietf.org/html/rfc2047#section-4.2">RFC 2047 section 4.2</a> for RFC details</remarks>
private static byte[] Rfc2047QuotedPrintableDecode(string toDecode, bool encodedWordVariant)
{
if (toDecode == null)
{
throw new ArgumentNullException("toDecode");
}
byte[] result;
using (MemoryStream byteArrayBuilder = new MemoryStream())
{
toDecode = QuotedPrintable.RemoveIllegalControlCharacters(toDecode);
for (int i = 0; i < toDecode.Length; i++)
{
char currentChar = toDecode[i];
if (currentChar == '=')
{
if (toDecode.Length - i < 3)
{
QuotedPrintable.WriteAllBytesToStream(byteArrayBuilder, QuotedPrintable.DecodeEqualSignNotLongEnough(toDecode.Substring(i)));
break;
}
string quotedPrintablePart = toDecode.Substring(i, 3);
QuotedPrintable.WriteAllBytesToStream(byteArrayBuilder, QuotedPrintable.DecodeEqualSign(quotedPrintablePart));
i += 2;
}
else if (currentChar == '_' && encodedWordVariant)
{
byteArrayBuilder.WriteByte(32);
}
else
{
byteArrayBuilder.WriteByte((byte)currentChar);
}
}
result = byteArrayBuilder.ToArray();
}
return(result);
}
