iTextSharp.text.pdf.SequenceList.Expand C# (CSharp) Метод

        public static ICollection<int> Expand(String ranges, int maxNumber)
        {
            SequenceList parse = new SequenceList(ranges);
            List<int> list = new List<int>();
            bool sair = false;
            while (!sair) {
                sair = parse.GetAttributes();
                if (parse.low == -1 && parse.high == -1 && !parse.even && !parse.odd)
                    continue;
                if (parse.low < 1)
                    parse.low = 1;
                if (parse.high < 1 || parse.high > maxNumber)
                    parse.high = maxNumber;
                if (parse.low > maxNumber)
                    parse.low = maxNumber;

                //System.out.Println("low="+parse.low+",high="+parse.high+",odd="+parse.odd+",even="+parse.even+",inverse="+parse.inverse);
                int inc = 1;
                if (parse.inverse) {
                    if (parse.low > parse.high) {
                        int t = parse.low;
                        parse.low = parse.high;
                        parse.high = t;
                    }
                    for (ListIterator<int> it = new ListIterator<int>(list); it.HasNext();) {
                        int n = it.Next();
                        if (parse.even && (n & 1) == 1)
                            continue;
                        if (parse.odd && (n & 1) == 0)
                            continue;
                        if (n >= parse.low && n <= parse.high)
                            it.Remove();
                    }
                }
                else {
                    if (parse.low > parse.high) {
                        inc = -1;
                        if (parse.odd || parse.even) {
                            --inc;
                            if (parse.even)
                                parse.low &= ~1;
                            else
                                parse.low -= ((parse.low & 1) == 1 ? 0 : 1);
                        }
                        for (int k = parse.low; k >= parse.high; k += inc) {
                            list.Add(k);
                        }
                    }
                    else {
                        if (parse.odd || parse.even) {
                            ++inc;
                            if (parse.odd)
                                parse.low |= 1;
                            else
                                parse.low += ((parse.low & 1) == 1 ? 1 : 0);
                        }
                        for (int k = parse.low; k <= parse.high; k += inc)
                            list.Add(k);
                    }
                }
            }
            return list;
        }

 /**
  * Concatenates a PDF document selecting the pages to keep. The pages are described as
  * ranges. The page ordering can be changed but
  * no page repetitions are allowed.
  * @param reader the PDF document
  * @param ranges the comma separated ranges as described in {@link SequenceList}
  * @throws DocumentException on error
  */
 public void AddDocument(PdfReader reader, String ranges)
 {
     fc.AddDocument(reader, SequenceList.Expand(ranges, reader.NumberOfPages));
 }