IgnoreWhitespaceStringComparer

IgnoreWhitespaceStringComparer.cs

using System;
using System.Collections.Generic;

namespace Sylvan
{
    public sealed class IgnoreWhitespaceStringComparer : IEqualityComparer<string>
    {
        public static readonly IEqualityComparer<string> Instance = new IgnoreWhitespaceStringComparer(0);
        public static readonly IEqualityComparer<string> IgnoreCase = new IgnoreWhitespaceStringComparer(0x20);

        private IgnoreWhitespaceStringComparer(int caseMask)
        {
            this.caseMask = caseMask;
        }

        readonly int caseMask;

        public bool Equals(string x, string y)
        {
            if (x == null)
            {
                return y == null;
            }
            else
            {
                if (y == null)
                    return false;
            }

            var xi = 0;
            var yi = 0;
            var xl = x.Length;
            var yl = y.Length;
            while (true)
            {
                var xc = -1;
                var yc = -1;
                while (xi < xl)
                {
                    var c = x[xi++];
                    if (!char.IsWhiteSpace(c))
                    {
                        xc = c;
                        break;
                    }
                }
                while (yi < yl)
                {
                    var c = y[yi++];
                    if (!char.IsWhiteSpace(c))
                    {
                        yc = c;
                        break;
                    }
                }

                if ((xc | caseMask) != (yc | caseMask))
                    return false;

                if (xc == -1 && yc == -1)
                    break;
            }
            return true;
        }

        public int GetHashCode(string obj)
        {
            if (obj == null) return 0;

            var hc = new HashCode();
            for (int i = 0; i < obj.Length; i++)
            {
                var c = obj[i];
                if (!char.IsWhiteSpace(c))
                {
                    hc.Add(c);
                }
            }
            return hc.ToHashCode();
        }
    }
}