Wildcard string compare (globbing)

Usage:

This is a fast, lightweight, and simple pattern matching function.

if (wildcmp("bl?h.*", "blah.jpg")) {
  //we have a match!
} else {
  //no match =(
}

Function:

int wildcmp(const char *wild, const char *string) {
  // Written by Jack Handy - <A href="mailto:jakkhandy@hotmail.com">jakkhandy@hotmail.com</A>
  const char *cp = NULL, *mp = NULL;

  while ((*string) && (*wild != '*')) {
    if ((*wild != *string) && (*wild != '?')) {
      return 0;
    }
    wild++;
    string++;
  }

  while (*string) {
    if (*wild == '*') {
      if (!*++wild) {
        return 1;
      }
      mp = wild;
      cp = string+1;
    } else if ((*wild == *string) || (*wild == '?')) {
      wild++;
      string++;
    } else {
      wild = mp;
      string = cp++;
    }
  }

  while (*wild == '*') {
    wild++;
  }
  return !*wild;
}

License

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About the Author

Jack Handy

Web Developer

United States

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Comments and Discussions

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I read this article " ,its really amazing. I appreciate your efforts. I am student, I need help in defining the same kind of function according to my requirements. I hope, I 'll get good response.

Words are strings which are separated by dots. Two additional characters are also valid i.e:The *, which matches 1 word and the #, which matches 0..N words Example: *.stock.# matches the routing keys usd.stock and eur.stock.dsf but not stock.nasdaq.

Your help would be highly appreciated.

Sam

A very useful function!
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First of all I like this code, it is small and fully stand-alone.
I have modified it, because I need an additional wildcard joker that represents digits. Finally the modified function accepts '*', '?' and '#' as joker characters.

int wildcmp_ex(const char *wild, const char *string) {
  const char *cp = NULL, *mp = NULL;
 
  while (*string) {
    if (*wild == '*') {
      if (!*++wild) {
        return 1;
      }
      mp = wild;
      cp = string+1;
    } else if (((*wild == *string) && (*wild != '#')) || (*wild == '?') || ((*wild == '#') && isdigit(*string))) {
      wild++;
      string++;
    } else {
      if (mp)
      {
        wild = mp;
        string = cp++;
      }
      else
      {
        return 0;
      }
    }
  }
 
  while (*wild == '*') {
    wild++;
  }
  return !*wild;
}

Thomas Haase

modified 29 Sep '11 - 8:26.

Hi Jack Handy, Is there a licence attached to this code? Thanks, Mark
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Just for fun... a C# version with almost the same syntax as the original C version Smile | :)

public static bool wildcmp(string pattern, string text) {
 
  var wild = new StringScanner(pattern);
  var @string = new StringScanner(text);
 
  var mp = wild;
  var cp = @string;
 
  while (@string && wild != '*') {
    if (wild != @string && wild != '?') {
      return false;
    }
    wild++;
    @string++;
  }
 
  while (@string) {
    if (@wild == '*') {
      if (!++wild) {
        return true;
      }
      mp = wild;
      cp = @string + 1;
    } else if (wild == @string || wild == '?') {
      wild++;
      @string++;
    } else {
      wild = mp;
      @string = cp++;
    }
  }
 
  while (wild == '*') {
    wild++;
  }
  return !wild;
}
 
public struct StringScanner
{
    private string _string;
    private int _position;
    
    public StringScanner(string s)
    {
        _string = s;
        _position = 0;
    }
    
    public string String
    {
        get { return _string; }
    }
    
    public int Position
    {
        get { return _position; }
    }
        
    public bool Finished
    {
        get { return _position == _string.Length;}
    }
    
    public char Current
    {
        get { return Finished ? '\0' : _string[_position]; }
    }
    
    public bool MoveNext()
    {
        if (Finished)
            return false;
        _position++;
        return true;
    }
    
    public static StringScanner operator ++(StringScanner scanner)
    {
        scanner.MoveNext();
        return scanner;
    }
    
    public static StringScanner operator +(StringScanner scanner, int n)
    {
        return new StringScanner(scanner.String)
        {
            _position = Math.Min(scanner.Position + n, scanner.String.Length)
        };
    }
    
    public static implicit operator bool(StringScanner scanner)
    {
        return !scanner.Finished;
    }
    
    public static implicit operator char(StringScanner scanner)
    {
        return scanner.Current;
    }
    
    public static bool operator ==(StringScanner scanner1, StringScanner scanner2)
    {
        return scanner1.Current == scanner2.Current;
    }
    
    public static bool operator !=(StringScanner scanner1, StringScanner scanner2)
    {
        return scanner1.Current != scanner2.Current;
    }
}

My blog : in English - in French

I've been using this for years, just don't show it to your instructor.

// String match with wildcards.  Obtained from the Internet somewhere.  Case insensitive.

BOOL wm(const char *s, const char *t)
{
	return *t-'*' ? *s ? (*t=='?') | (toupper(*s)==toupper(*t)) && wm(s+1,t+1) : !*t : wm(s,t+1) || *s && wm(s+1,t);
}

If you want case sensitive, remove the toupper() calls.

This strikes me as an obvious place to use recursion. So here goes...

   public class MString
   {
      /// <summary>
      /// Function to compare two strings, where strA may contain wildcard characters '*' and 
      /// '?'. http://en.wikipedia.org/wiki/Wildcard_character
      /// </summary>
      /// <param name="strA">string which may contain wildcards, may be empty, must not be null</param>
      /// <param name="strB">string to compare to, no wildcard processing, may be empty, must not be null</param>
      /// <param name="ignoreCase">true = ignore upper/lower case, false = don't ignore case</param>
      /// <returns>true = match, false = non-match</returns>
      public static bool CompareWWc(string strA, string strB, bool ignoreCase)
      {
         if (ignoreCase)
            return CompareWWc(strA.ToLower(), strB.ToLower());
         else 
            return CompareWWc(strA, strB);
      }
 

      /// <summary>
      /// Recursive function to compare two strings, where strA may contain wildcard characters 
      /// '*' and '?'. http://en.wikipedia.org/wiki/Wildcard_character
      /// </summary>
      /// <param name="strA">string which may contain wildcards, may be empty, must not be null</param>
      /// <param name="strB">string to compare to, no wildcard processing, may be empty, must not be null</param>
      /// <returns>true = match, false = non-match</returns>
      public static bool CompareWWc(string strA, string strB)
      {
         // Top of loop to scan across strA (and strB)
         for (int i = 0; i < strA.Length; i++)
         {
            // Special processing when we hit a '*' in strA
            if (strA[i] == '*')
            {
               // If the '*' is at the end of strA then result = true irrespective of strB
               if (i == strA.Length - 1)
                  return true;  
 
               // Do recursive calls to try to find a match somewhere to the right in strB
               strA = strA.Substring(i + 1);  // The part of strA beyond the '*'
               for (int j = i; j < strB.Length; j++)
                  if (CompareWWc(strA, strB.Substring(j)))
                     return true;
               return false;
            }
 
            // Normal processing for non-'*' characters in strA
            if (i >= strB.Length || (strA[i] != strB[i] && strA[i] != '?'))
               return false;
         }
 
         // We've reached the end of strA and the last character is not '*'
         return strA.Length == strB.Length;
      }
 
   }

And here's a little test sequence:

         if (!MString.CompareWWc("", ""))
            Console.WriteLine("Something wrong!");
 

         if (!MString.CompareWWc("something", "something"))
            Console.WriteLine("Something wrong!");
 
         if (MString.CompareWWc("something", "zomething"))
            Console.WriteLine("Something wrong!");
         
         if (MString.CompareWWc("something", "some"))
            Console.WriteLine("Something wrong!");
         
         if (MString.CompareWWc("something", "something else"))
            Console.WriteLine("Something wrong!");
 

         if (!MString.CompareWWc("s?m?th???", "something"))
            Console.WriteLine("Something wrong!");
         
         if (MString.CompareWWc("s?m?th???", "somethin"))
            Console.WriteLine("Something wrong!");
 

         if (!MString.CompareWWc("*", ""))
            Console.WriteLine("Something wrong!");
         
         if (!MString.CompareWWc("*", "nonsense"))
            Console.WriteLine("Something wrong!");
         
         if (!MString.CompareWWc("non*", "nonsense"))
            Console.WriteLine("Something wrong!");
 

         if (!MString.CompareWWc("*nonsense", "nonsense"))
            Console.WriteLine("Something wrong!");
 
         if (!MString.CompareWWc("non*nse", "nonsense"))
            Console.WriteLine("Something wrong!");
         
         if (MString.CompareWWc("non*nse", "nonsenze"))
            Console.WriteLine("Something wrong!");
         
         if (!MString.CompareWWc("non*n?e", "nonsense"))
            Console.WriteLine("Something wrong!");
 

         if (!MString.CompareWWc("n*on*nse", "nonsense"))
            Console.WriteLine("Something wrong!");
 
         if (!MString.CompareWWc("n*n*nse", "nonsense"))
            Console.WriteLine("Something wrong!");
 
         if (MString.CompareWWc("*non*nse", "nonsenze"))
            Console.WriteLine("Something wrong!");
 
         if (!MString.CompareWWc("n*n*n?e", "nonsense"))
            Console.WriteLine("Something wrong!");
      }

By the way, the name CompareWWc means Compare With Wildcards.

Actually, the recursive function together with substring will make this slow.
I'm using this at the moment:

    public static class StringExtensions
    {
        public static bool WildcardMatch(this string str, string compare, bool ignoreCase) 
        { 
            if (ignoreCase)
                return str.ToLower().WildcardMatch(compare.ToLower()); 
            else
                return str.WildcardMatch(compare); 
        }
 
        public static bool WildcardMatch(this string str, string compare)
        {
            if (string.IsNullOrEmpty(compare))
                return str.Length == 0;
            int pS = 0;
            int pW = 0;
            int lS = str.Length;
            int lW = compare.Length;
            
            while (pS < lS && pW < lW && compare[pW] != '*')
            {
                char wild = compare[pW];
                if (wild != '?' && wild != str[pS])
                    return false;
                pW++;
                pS++;
            }
 
            int pSm = 0;
            int pWm = 0;
            while (pS < lS && pW < lW)
            {
                char wild = compare[pW];
                if (wild == '*')
                {
                    pW++;
                    if (pW == lW)
                        return true;
                    pWm = pW;
                    pSm = pS + 1;
                }
                else if (wild == '?' || wild == str[pS])
                {
                    pW++;
                    pS++;
                }
                else
                {
                    pW = pWm;
                    pS = pSm;
                    pSm++;
                }
            }
            while (pW < lW && compare[pW] == '*')
                pW++;
            return pW == lW && pS == lS; 
        }
    }

Hi Erwin,

Thanks for your posting. It did make me decide to investigate the situation.

I still really think this is a situation that begs for recursion. But maybe you were right that substring is not a good idea. So I made this version:

   public class MString2
   {
      /// <summary>
      /// Function to compare two strings, where strA may contain wildcard characters '*' and 
      /// '?'. http://en.wikipedia.org/wiki/Wildcard_character
      /// </summary>
      /// <param name="strA">string which may contain wildcards, may be empty, must not be null</param>
      /// <param name="strB">string to compare to, no wildcard processing, may be empty, must not be null</param>
      /// <param name="ignoreCase">true = ignore upper/lower case, false = don't ignore case</param>
      /// <returns>true = match, false = non-match</returns>
      public static bool CompareWWc(string strA, string strB, bool ignoreCase)
      {
         if (ignoreCase)
            return CompareWWc(strA.ToLower(), 0, strB.ToLower(), 0);
         else
            return CompareWWc(strA, 0, strB, 0);
      }
 

      /// <summary>
      /// Function to compare two strings, where strA may contain wildcard characters '*' and 
      /// '?'. http://en.wikipedia.org/wiki/Wildcard_character
      /// </summary>
      /// <param name="strA">string which may contain wildcards, may be empty, must not be null</param>
      /// <param name="strB">string to compare to, no wildcard processing, may be empty, must not be null</param>
      /// <returns>true = match, false = non-match</returns>
      public static bool CompareWWc(string strA, string strB)
      {
         // Just call the private recursive version of this function
         return CompareWWc(strA, 0, strB, 0);
      }
 

      /// <summary>
      /// Private recursive function used by the above two public functions.
      /// </summary>
      /// <param name="strA">string which may contain wildcards, may be empty, must not be null</param>
      /// <param name="indexA">index into strA marking start of the string for processing purposes</param>
      /// <param name="strB">string to compare to, no wildcard processing, may be empty, must not be null</param>
      /// <param name="indexB">index into strB marking start of the string for processing purposes</param>
      /// <returns>true = match, false = non-match</returns>
      private static bool CompareWWc(string strA, int indexA, string strB, int indexB)
      {
         // Top of loop to scan across strA (and strB)
         for (int i = 0; indexA + i < strA.Length; i++)
         {
            // Special processing when we hit a '*' in strA
            if (strA[indexA + i] == '*')
            {
               // If the '*' is at the end of strA then result = true irrespective of strB
               if (indexA + i == strA.Length - 1)
                  return true;
 
               // Do recursive calls to try to find a match somewhere to the right in strB
               for (int j = indexB + i; j < strB.Length; j++)
                  if (CompareWWc(strA, indexA + i + 1, strB, j))
                     return true;
               return false;
            }
 
            // Normal processing for non-'*' characters in strA
            if (indexB + i >= strB.Length || (strA[indexA + i] != strB[indexB + i] && strA[indexA + i] != '?'))
               return false;
         }
 
         // We've reached the end of strA and there is no '*' in strA
         return strA.Length - indexA == strB.Length - indexB;
      }
      
   }

Then I ran some timing tests, using System.Diagnostics.Stopwatch. I put my test case with 19 calls to the function in a loop and executed it 10,000 times. I did this for my original version, your version, and my new version. I compiled the programs in Release mode.

Assuming I haven't made a mistake somewhere, here are my results for a single function call:

My original version:  342 nonoseconds
Your version:         237 nanoseconds
My second version:    279 nanoseconds

Now to tell you the truth, I find it very difficult to get excited about saving 100 nanoseconds at the expense of having two and a half times as many lines of code. Especially since my expected use of this function in my application will probably never exceed a couple hundred calls per day. Smile | :)

Anyway, thanks for getting me to think things over again and make the tests. Personally, at least in this particular case, I prefer programmer understandability to execution efficiency. I've decided to stick with my original version, since I think my second version is more difficult to understand, and the improved efficiency not worth that disadvantage.

Hi Erwin,

Sorry - my previous numbers are not correct. I was running the programs under the Visual Studio debugger, and that was apparently not good for timing tests.

Here's what I get now:

My original version:  243 nonoseconds
Your version:          76 nanoseconds
My second version:    111 nanoseconds

Assuming these timings are valid, your version is three times faster than my original version, and that is pretty significant, at least in a situation were the function may be used millions times a day.

Sorry for the incorrect timings in my previous posting.