internal static string DecodeHeaderValue(string value)
{
if (string.IsNullOrEmpty(value))
{
return(string.Empty);
}
string newValue = string.Empty;
//split strings, they may be folded. If they are, decode one at a time and append the results
string[] substringsToDecode = value.Split(s_headerValueSplitChars, StringSplitOptions.RemoveEmptyEntries);
foreach (string foldedSubString in substringsToDecode)
{
//an encoded string has as specific format in that it must start and end with an
//'=' char and contains five parts, separated by '?' chars.
//the first and last part are therefore '=', the second part is the byte encoding (B or Q)
//the third is the unicode encoding type, and the fourth is encoded message itself. '?' is not valid inside of
//an encoded string other than as a separator for these five parts.
//If this check fails, the string is either not encoded or cannot be decoded by this method
string[] subStrings = foldedSubString.Split(s_questionMarkSplitChars);
if ((subStrings.Length != 5 || subStrings[0] != "=" || subStrings[4] != "="))
{
return(value);
}
string charSet = subStrings[1];
bool base64Encoding = (subStrings[2] == "B");
byte[] buffer = Encoding.ASCII.GetBytes(subStrings[3]);
int newLength;
EncodedStreamFactory encoderFactory = new EncodedStreamFactory();
IEncodableStream s = encoderFactory.GetEncoderForHeader(Encoding.GetEncoding(charSet), base64Encoding, 0);
newLength = s.DecodeBytes(buffer, 0, buffer.Length);
Encoding encoding = Encoding.GetEncoding(charSet);
newValue += encoding.GetString(buffer, 0, newLength);
}
return(newValue);
}
//used when the length of the header name itself is known (i.e. Subject : )
internal static string EncodeHeaderValue(string value, Encoding encoding, bool base64Encoding, int headerLength)
{
StringBuilder newString = new StringBuilder();
//no need to encode if it's pure ascii
if (IsAscii(value, false))
{
return(value);
}
if (encoding == null)
{
encoding = Encoding.GetEncoding(MimeBasePart.defaultCharSet);
}
EncodedStreamFactory factory = new EncodedStreamFactory();
IEncodableStream stream = factory.GetEncoderForHeader(encoding, base64Encoding, headerLength);
byte[] buffer = encoding.GetBytes(value);
stream.EncodeBytes(buffer, 0, buffer.Length);
return(stream.GetEncodedString());
}
public void EncodedStreamFactory_WhenAskedForEncodedStreamForHeader_WithBase64_ShouldReturnBase64Stream()
{
IEncodableStream test = EncodedStreamFactory.GetEncoderForHeader(Encoding.UTF8, true, 5);
Assert.True(test is Base64Stream);
}
