C# StrCmpLogical

StrCmpLogical.cs

        static bool IsDigit(char c)
        {
            return c >= '0' && c <= '9';
        }

        unsafe static int UnsafeStrCmpLogical(string s1, string s2)
        {
            fixed (char* p1 = s1)
            {
                fixed (char* p2 = s2)
                {
                    char* x = p1;
                    char* y = p2;
                    while (*x != '\0' && *y != '\0')
                    {
                        char a = *x;
                        char b = *y;
                        if (!(IsDigit(a) && IsDigit(b)))
                        {
                            if (a > b)
                                return 1;
                            if (a < b)
                                return -1;
                            x++;
                            y++;
                        }
                        else
                        {
                            bool zero = true;
                            char* m = x;
                            while (IsDigit(*m))
                            {
                                if (*m == '0' && zero)
                                    x++;
                                else
                                    zero = false;
                                m++;
                            }

                            zero = true;
                            char* n = y;
                            while (IsDigit(*n))
                            {
                                if (*n == '0' && zero)
                                    y++;
                                else
                                    zero = false;
                                n++;
                            }

                            if (m - x > n - y)
                                return 1;
                            else if (m - x < n - y)
                                return -1;

                            while (x < m)
                            {
                                if (*x > *y)
                                    return 1;
                                if (*x < *y)
                                    return -1;
                                x++;
                                y++;
                            }
                        }
                    }

                    if (*x > *y)
                        return 1;
                    if (*x < *y)
                        return -1;
                    return 0;
                }
            }
        }

        static int SafeStrCmpLogical(string s1, string s2)
        {
            int x = 0;
            int y = 0;
            while (s1[x] != '\0' && s2[y] != '\0')
            {
                char a = s1[x];
                char b = s2[y];
                if (!(IsDigit(a) && IsDigit(b)))
                {
                    if (a > b)
                        return 1;
                    if (a < b)
                        return -1;
                    x++;
                    y++;
                }
                else
                {
                    bool zero = true;
                    int m = x;
                    while (IsDigit(s1[m]))
                    {
                        if (s1[m] == '0' && zero)
                            x++;
                        else
                            zero = false;
                        m++;
                    }

                    zero = true;
                    int n = y;
                    while (IsDigit(s2[n]))
                    {
                        if (s2[n] == '0' && zero)
                            y++;
                        else
                            zero = false;
                        n++;
                    }

                    if (m - x > n - y)
                        return 1;
                    else if (m - x < n - y)
                        return -1;

                    while (x < m)
                    {
                        if (s1[x] > s2[y])
                            return 1;
                        if (s1[x] < s2[y])
                            return -1;
                        x++;
                        y++;
                    }
                }
            }

            if (s1[x] > s2[y])
                return 1;
            if (s1[x] < s2[y])
                return -1;
            return 0;
        }

Note that it is totally different from win32 API StrCmpLogicalW