StringLogicalComparer.cs

using System;
using System.Collections;
using System.Windows.Forms;

namespace TheraWii
{
	class ListComparer : IComparer
	{
		private int col;
        public ListComparer()
        {
            col = 0;
        }
        public ListComparer(int column)
        {
            col = column;
        }
        public int Compare(object x, object y)
        {
			int c = StringLogicalComparer.Compare(((ListViewItem)x).SubItems[col].Text, ((ListViewItem)y).SubItems[col].Text);
			if (((ListViewItem)x).ListView.Sorting == SortOrder.Descending)
			{
				return c * -1;
			}
			return c;
        }
	}


	public sealed class StringLogicalComparer : IComparer
	{
		private static readonly IComparer _default = new StringLogicalComparer();
		private static readonly IComparer _defaultZeroesFirst = new StringLogicalComparer(true);
		private bool zeroesFirst = false;

		private StringLogicalComparer()
		{ }

		private StringLogicalComparer(bool zeroesFirst)
		{
			this.zeroesFirst = zeroesFirst;
		}

		public static IComparer Default
		{
			get { return _default; }
		}

		public static IComparer DefaultZeroesFirst
		{
			get { return _defaultZeroesFirst; }
		}

		public int Compare(object x, object y)
		{
			if (null == x && null == y) return 0;
			if (null == x) return -1;
			if (null == y) return 1;
			if (x is string && y is string)
				return Compare((string)x, (string)y, zeroesFirst);
			return Comparer.Default.Compare(x, y);
		}

		public static int Compare(string s1, string s2)
		{
			return Compare(s1, s2, false);
		}

		public static int Compare(string s1, string s2, bool zeroesFirst)
		{
			//get rid of special cases
			if ((s1 == null) && (s2 == null)) return 0;
			else if (s1 == null) return -1;
			else if (s2 == null) return 1;

			if ((s1.Length <= 0) && (s2.Length <= 0)) return 0;
			else if (s1.Length <= 0) return -1;
			else if (s2.Length <= 0) return 1;

			//special case
			bool sp1 = Char.IsLetterOrDigit(s1[0]);
			bool sp2 = Char.IsLetterOrDigit(s2[0]);
			if (sp1 && !sp2) return 1;
			if (!sp1 && sp2) return -1;

			int i1 = 0, i2 = 0; //current index
			int r = 0; // temp result
			char c1, c2;
			bool letter1, letter2;

			while (true)
			{
				c1 = s1[i1];
				c2 = s2[i2];
				sp1 = Char.IsDigit(c1);
				sp2 = Char.IsDigit(c2);
				if (!sp1 && !sp2)
				{
					letter1 = Char.IsLetter(c1);
					letter2 = Char.IsLetter(c2);

					if (letter1 && letter2)
					{
						r = Char.ToUpper(c1).ToString().CompareTo(Char.ToUpper(c2).ToString());
						if (r != 0) return r;
					}
					else if (!letter1 && !letter2)
					{
						r = c1.CompareTo(c2);
						if (r != 0) return r;
					}
					else if (!letter1 && letter2)
					{
						return -1;
					}
					else if (letter1 && !letter2)
					{
						return 1;
					}
				}
				else if (sp1 && sp2)
				{
					r = CompareNum(s1, ref i1, s2, ref i2, zeroesFirst);
					if (r != 0) return r;
				}
				else if (sp1)
				{
					return -1;
				}
				else if (sp2)
				{
					return 1;
				}
				i1++;
				i2++;
				if ((i1 >= s1.Length) && (i2 >= s2.Length))
				{
					return 0;
				}
				else if (i1 >= s1.Length)
				{
					return -1;
				}
				else if (i2 >= s2.Length)
				{
					return 1;
				}
			}
		}

		private static int CompareNum(string s1, ref int i1, string s2, ref int i2, bool zeroesFirst)
		{
			int nzStart1 = i1, nzStart2 = i2; // nz = non zero
			int end1 = i1, end2 = i2;

			ScanNumEnd(s1, i1, ref end1, ref nzStart1);
			ScanNumEnd(s2, i2, ref end2, ref nzStart2);
			int start1 = i1; i1 = end1 - 1;
			int start2 = i2; i2 = end2 - 1;

			if (zeroesFirst)
			{
				int zl1 = nzStart1 - start1;
				int zl2 = nzStart2 - start2;
				if (zl1 > zl2) return -1;
				if (zl1 < zl2) return 1;
			}

			int nzLength1 = end1 - nzStart1;
			int nzLength2 = end2 - nzStart2;

			if (nzLength1 < nzLength2) return -1;
			else if (nzLength1 > nzLength2) return 1;

			for (int j1 = nzStart1, j2 = nzStart2; j1 <= i1; j1++, j2++)
			{
				int r = s1[j1].CompareTo(s2[j2]);
				if (r != 0) return r;
			}
			// the nz parts are equal
			int length1 = end1 - start1;
			int length2 = end2 - start2;
			if (length1 == length2) return 0;
			if (length1 > length2) return -1;
			return 1;
		}

		//lookahead
		private static void ScanNumEnd(string s, int start, ref int end, ref int nzStart)
		{
			nzStart = start;
			end = start;
			bool countZeros = true;
			while (Char.IsDigit(s, end))
			{
				if (countZeros && s[end].Equals('0'))
				{
					nzStart++;
				}
				else countZeros = false;
				end++;
				if (end >= s.Length) break;
			}
		}

	}//EOC
}