static bool GetNextValue (string charset, Encoder encoder, HexEncoder hex, char[] chars, ref int index,
ref byte[] bytes, ref byte[] encoded, int maxLength, out string value)
{
int length = chars.Length - index;
if (length < maxLength) {
switch (GetEncodeMethod (chars, index, length)) {
case EncodeMethod.Quote:
value = MimeUtils.Quote (new string (chars, index, length));
index += length;
return false;
case EncodeMethod.None:
value = new string (chars, index, length);
index += length;
return false;
}
}
length = Math.Min (maxLength, length);
int ratio, count, n;
do {
count = encoder.GetByteCount (chars, index, length, true);
if (count > maxLength && length > 1) {
ratio = (int) Math.Round ((double) count / (double) length);
length -= Math.Max ((count - maxLength) / ratio, 1);
continue;
}
if (bytes.Length < count)
Array.Resize<byte> (ref bytes, count);
count = encoder.GetBytes (chars, index, length, bytes, 0, true);
// Note: the first chunk needs to be encoded in order to declare the charset
if (index > 0 || charset == "us-ascii") {
var method = GetEncodeMethod (bytes, count);
if (method == EncodeMethod.Quote) {
value = MimeUtils.Quote (Encoding.ASCII.GetString (bytes, 0, count));
index += length;
return false;
}
if (method == EncodeMethod.None) {
value = Encoding.ASCII.GetString (bytes, 0, count);
index += length;
return false;
}
}
n = hex.EstimateOutputLength (count);
if (encoded.Length < n)
Array.Resize<byte> (ref encoded, n);
// only the first value gets a charset declaration
int charsetLength = index == 0 ? charset.Length + 2 : 0;
n = hex.Encode (bytes, 0, count, encoded);
if (n > 3 && (charsetLength + n) > maxLength) {
int x = 0;
for (int i = n - 1; i >= 0 && charsetLength + i >= maxLength; i--) {
if (encoded[i] == (byte) '%')
x--;
else
x++;
}
ratio = (int) Math.Round ((double) count / (double) length);
length -= Math.Max (x / ratio, 1);
continue;
}
if (index == 0)
value = charset + "''" + Encoding.ASCII.GetString (encoded, 0, n);
else
value = Encoding.ASCII.GetString (encoded, 0, n);
index += length;
return true;
} while (true);
}
internal void Encode (FormatOptions options, StringBuilder builder, ref int lineLength, Encoding encoding)
{
string quoted;
var method = GetEncodeMethod (options, Name, Value, out quoted);
if (method == EncodeMethod.None)
quoted = Value;
if (method != EncodeMethod.Rfc2184) {
if (lineLength + 2 + Name.Length + 1 + quoted.Length >= options.MaxLineLength) {
builder.Append (";\n\t");
lineLength = 1;
} else {
builder.Append ("; ");
lineLength += 2;
}
lineLength += Name.Length + 1 + quoted.Length;
builder.Append (Name);
builder.Append ('=');
builder.Append (quoted);
return;
}
int maxLength = options.MaxLineLength - (Name.Length + 6);
var bestEncoding = GetBestEncoding (Value, encoding);
var charset = CharsetUtils.GetMimeCharset (bestEncoding);
var bytes = new byte[Math.Max (maxLength, 6)];
var hexbuf = new byte[bytes.Length * 3 + 3];
var encoder = bestEncoding.GetEncoder ();
var chars = Value.ToCharArray ();
var hex = new HexEncoder ();
int index = 0, i = 0;
string value, id;
bool encoded;
int length;
do {
encoded = GetNextValue (charset, encoder, hex, chars, ref index, ref bytes, ref hexbuf, maxLength, out value);
length = Name.Length + (encoded ? 1 : 0) + 1 + value.Length;
if (i == 0 && index == chars.Length) {
if (lineLength + 2 + length >= options.MaxLineLength) {
builder.Append (";\n\t");
lineLength = 1;
} else {
builder.Append ("; ");
lineLength += 2;
}
builder.Append (Name);
if (encoded)
builder.Append ('*');
builder.Append ('=');
builder.Append (value);
lineLength += length;
return;
}
builder.Append (";\n\t");
lineLength = 1;
id = i.ToString ();
length += id.Length + 1;
builder.Append (Name);
builder.Append ('*');
builder.Append (id);
if (encoded)
builder.Append ('*');
builder.Append ('=');
builder.Append (value);
lineLength += length;
i++;
} while (index < chars.Length);
}
void EncodeRfc2231 (FormatOptions options, StringBuilder builder, ref int lineLength, Encoding headerEncoding)
{
var bestEncoding = options.International ? CharsetUtils.UTF8 : GetBestEncoding (Value, encoding ?? headerEncoding);
int maxLength = options.MaxLineLength - (Name.Length + 6);
var charset = CharsetUtils.GetMimeCharset (bestEncoding);
var encoder = (Encoder) bestEncoding.GetEncoder ();
var bytes = new byte[Math.Max (maxLength, 6)];
var hexbuf = new byte[bytes.Length * 3 + 3];
var chars = Value.ToCharArray ();
var hex = new HexEncoder ();
int index = 0, i = 0;
string value, id;
bool encoded;
int length;
do {
builder.Append (';');
lineLength++;
encoded = Rfc2231GetNextValue (options, charset, encoder, hex, chars, ref index, ref bytes, ref hexbuf, maxLength, out value);
length = Name.Length + (encoded ? 1 : 0) + 1 + value.Length;
if (i == 0 && index == chars.Length) {
if (lineLength + 1 + length >= options.MaxLineLength) {
builder.Append (options.NewLine);
builder.Append ('\t');
lineLength = 1;
} else {
builder.Append (' ');
lineLength++;
}
builder.Append (Name);
if (encoded)
builder.Append ('*');
builder.Append ('=');
builder.Append (value);
lineLength += length;
return;
}
builder.Append (options.NewLine);
builder.Append ('\t');
lineLength = 1;
id = i.ToString ();
length += id.Length + 1;
builder.Append (Name);
builder.Append ('*');
builder.Append (id);
if (encoded)
builder.Append ('*');
builder.Append ('=');
builder.Append (value);
lineLength += length;
i++;
} while (index < chars.Length);
}
