OpenTween.Twitter.PreProcessUrl C# (CSharp) Method

        public string PreProcessUrl(string orgData)
        {
            int posl1;
            var posl2 = 0;
            //var IDNConveter = new IdnMapping();
            var href = "<a href=\"";

            while (true)
            {
                if (orgData.IndexOf(href, posl2, StringComparison.Ordinal) > -1)
                {
                    var urlStr = "";
                    // IDN展開
                    posl1 = orgData.IndexOf(href, posl2, StringComparison.Ordinal);
                    posl1 += href.Length;
                    posl2 = orgData.IndexOf("\"", posl1, StringComparison.Ordinal);
                    urlStr = orgData.Substring(posl1, posl2 - posl1);

                    if (!urlStr.StartsWith("http://", StringComparison.Ordinal)
                        && !urlStr.StartsWith("https://", StringComparison.Ordinal)
                        && !urlStr.StartsWith("ftp://", StringComparison.Ordinal))
                    {
                        continue;
                    }

                    var replacedUrl = MyCommon.IDNEncode(urlStr);
                    if (replacedUrl == null) continue;
                    if (replacedUrl == urlStr) continue;

                    orgData = orgData.Replace("<a href=\"" + urlStr, "<a href=\"" + replacedUrl);
                    posl2 = 0;
                }
                else
                {
                    break;
                }
            }
            return orgData;
        }