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Wildcard string compare (globbing)

, 15 Feb 2005
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Matches a string against a wildcard string such as "*.*" or "bl?h.*" etc. This is good for file globbing or to match hostmasks.

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

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

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About the Author

Jack Handy
Web Developer
United States United States
No Biography provided

Comments and Discussions

 
AnswerMy C# contribution - recursive, of course! PinmemberRenniePet26-Mar-10 5:21 
GeneralRe: My C# contribution - recursive, of course! PinmemberErwin de GRoot29-Mar-10 1:58 
GeneralDepends on whether you need to optimize the last few nanoseconds out of it... PinmemberRenniePet29-Mar-10 7:45 
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.
GeneralSorry - revised numbers PinmemberRenniePet29-Mar-10 8:35 
GeneralRe: Depends on whether you need to optimize the last few nanoseconds out of it... PinmemberErwin de GRoot29-Mar-10 8:37 
GeneralYet another version - 25% faster, I think [modified] PinmemberRenniePet1-Apr-10 8:24 
GeneralRe: Yet another version - 25% faster, I think Pinmemberaleks1k21-Sep-11 2:47 

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