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);
}
