QuickFix.Message.SetGroup C# (CSharp) Method

        protected int SetGroup(StringField grpNoFld, string msgstr, int pos, FieldMap fieldMap, DataDictionary.IGroupSpec dd, DataDictionary.DataDictionary sessionDataDictionary, DataDictionary.DataDictionary appDD)
        {
            int delim = dd.Delim;
            int grpPos = pos;
            Group grp = null;

            while (pos < msgstr.Length)
            {
                grpPos = pos;
                StringField f = ExtractField(msgstr, ref pos, sessionDataDictionary, appDD);
                if (f.Tag == delim)
                {
                    if (grp != null)
                    {
                        fieldMap.AddGroup(grp);
                    }
                    grp = new Group(grpNoFld.Tag, delim);
                }
                else if (!dd.IsField(f.Tag))
                {
                    if (grp != null)
                    {
                        fieldMap.AddGroup(grp);
                    }
                    return grpPos;
                }
                grp.SetField(f);
                if(dd.IsGroup(f.Tag))
                {
                    pos = SetGroup(f, msgstr, pos, grp, dd.GetGroupSpec(f.Tag), sessionDataDictionary, appDD);
                }
            }

            return grpPos;
        }