DocSpace-client/common/ASC.Common/Utils/MimeHeaderUtils.cs

namespace ASC.Common.Utils;

public static class MimeHeaderUtils
{
    public static string EncodeMime(string mimeHeaderValue)
    {
        return EncodeMime(mimeHeaderValue, Encoding.UTF8, false);
    }

    public static string EncodeMime(string mimeHeaderValue, Encoding charset, bool split)
    {
        if (MustEncode(mimeHeaderValue))
        {
            var result = new StringBuilder();
            var data = charset.GetBytes(mimeHeaderValue);
            var maxEncodedTextSize = split ? 75 - ("=?" + charset.WebName + "?" + "B"/*Base64 encode*/ + "?" + "?=").Length : int.MaxValue;

            result.Append("=?" + charset.WebName + "?B?");
            var stored = 0;
            var base64 = Convert.ToBase64String(data);

            for (var i = 0; i < base64.Length; i += 4)
            {
                // Encoding buffer full, create new encoded-word.
                if (stored + 4 > maxEncodedTextSize)
                {
                    result.Append("?=\r\n =?" + charset.WebName + "?B?");
                    stored = 0;
                }

                result.Append(base64, i, 4);
                stored += 4;
            }

            result.Append("?=");

            return result.ToString();
        }

        return mimeHeaderValue;
    }

    public static bool MustEncode(string text)
    {
        return !string.IsNullOrEmpty(text) && text.Any(c => c > 127);
    }
}