Regex Matcher

/* Regex Pattern Matching

Handles ^, $ and *

*/

using System;

namespace StringHelper

{

public static partial class RegexMatcher

{

public static bool IsMatch(char[] str, char[] pattern)

{

if (pattern[0] == '^')

return IsMatch(str, 0, pattern, 1);

for (int i = 0; i < str.Length; i++)

{

if (IsMatch(str, i, pattern, 0)) return true;

}

return false;

}

// handle ? *

public static bool IsMatch(char[] str, int si, char[] pattern, int pi)

{

// pattern is over. IsMatch is true.

if (pattern == null || pi >= pattern.Length) return true;

if (pattern[pi] == '$')

{

if (si == str.Length) return true;

else return false;

}

// pattern is not over.

if (si >= str.Length) return false;

// pattern is not exhausted and str is not exhausted.

if (pattern[pi] == '?')

return IsMatch(str, si + 1, pattern, pi + 1) || IsMatch(str, si, pattern, pi + 1);

if (pattern[pi] == '*')

{

for (int i = si; i < str.Length; i++)

if (IsMatch(str, i, pattern, pi + 1)) return true;

}

if (pattern[pi] == str[si])

return IsMatch(str, si + 1, pattern, pi + 1);

return false;

}

}

}