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Wildcard string compare (globbing)

By , 15 Feb 2005
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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.

A list of licenses authors might use can be found here

About the Author

Jack Handy
Web Developer
United States United States
No Biography provided

Comments and Discussions

 
QuestionMy vote of 5+ PinmemberSanmayce29-Nov-13 7:47 
GeneralMy vote of 5 PinmemberFranc Morales29-May-13 15:47 
Questionhelp required for wilcard matching * and # PinmemberSaimaAsif23-Feb-12 23:56 
GeneralMy vote of 5 PinmemberPlamen Petrov13-Dec-11 21:37 
SuggestionModification with '#' as wildcard joker for digits [modified] PinmemberThomas Haase25-Sep-11 23:16 
QuestionLicence Question Pinmemberrandommark23-Nov-10 0:33 
AnswerAnother C# version, with a twist Pinmembertomlev29-Jun-10 14:50 
GeneralObscurity PinmemberChuck O'Toole25-Apr-10 18:18 
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 
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 
If at first you don't succeed...
 
Here's my third version, where I say to hell with minimizing lines of code and try to optimize the speed. No "unsafe" code though, unless you consider "goto" to be unsafe coding. Smile | :)
 
   public class MString
   {
      /// <summary>
      /// Compare two strings, where strA may contain wildcard characters '*' and '?'. 
      /// </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 = observe 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>
      /// Compare two strings, where strA may contain wildcard characters '*' and '?'. 
      /// 
      /// In the comments, the word 'segment' is used to talk about the portions of strA that
      /// fall between two '*' characters, or between the start of the string and the first '*'
      /// or between the last '*' and the end of the string.
      /// </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)
      {
         int starPtr = 0;  // Points at the '*' in strA

         // This part of the code handles the first segment in strA, or the case where strA
         //  does not contain any '*' character at all. The first segment is fairly simple to
         //  handle because it must match from the start of strB - no need to have a sliding 
         //  match loop.

         // Check strB long enough so we don't need to test for hitting its end while scanning
         if (strB.Length >= strA.Length)
         {
            // Simple optimized scan of first segment of strA and comparison with strB
            for (;; starPtr++)
            {
               if (starPtr == strA.Length)
                  return strA.Length == strB.Length;  // No '*' in strA and no mismatch
               if (strA[starPtr] == '*')
                  goto firstSegmentMatches;
               if (strA[starPtr] != strB[starPtr] && strA[starPtr] != '?')
                  return false;  // Mismatch
            }
         }
         else
         {
            // When strB is shorter than strA a match is not likely. But if strA contains 
            //  enough '*' characters it is possible, so we have to give it a try.
            for (;; starPtr++)
            {
               if (strA[starPtr] == '*')
                  goto firstSegmentMatches;
               if (starPtr == strB.Length)
                  return false;  // No '*' in strA before end of strB encountered
               if (strA[starPtr] != strB[starPtr] && strA[starPtr] != '?')
                  return false;  // Mismatch
            }
         }
 
         // The rest of the code handles the case where strA does contain one or more '*' 
         //  characters, and the first segment does match the start of strB.

      firstSegmentMatches:
 
         int indexA;  // Start of segment in strA
         int indexB = starPtr;  // Sliding match location in strB
         
         // Loop to process the segments in strA
         while (true)
         {
            // Test if next segment is last and empty
            indexA = ++starPtr;  // Point past '*'
            if (indexA == strA.Length)
               return true;  // Last segment empty - matches irrespective of strB content

            // Scan over the next segment in strA
            for (;; starPtr++)
               if (starPtr == strA.Length || strA[starPtr] == '*')
                  break;
 
            // Try to find match for this segment somewhere in strB
            for (;; indexB++)
            {
               if (starPtr - indexA > strB.Length - indexB)
                  return false;  // Mismatch if not enough characters left in strB

               for (int i = indexA, j = indexB; i < starPtr; i++, j++)
                  if (strA[i] != strB[j] && strA[i] != '?')
                     goto tryStringBAgain;
               
               goto findNextSegment;  // Match found for this segment in strB 

            tryStringBAgain:
               continue;
            }
 
            // Was that last segment? Return if so, loop if not.
         findNextSegment:
            indexB += starPtr - indexA;  // Point past matching portion of strB
            if (starPtr == strA.Length)
               return indexB == strB.Length;  // Return if that was last segment
         }
      }
 
   }
 
And here are my timing results (which I'm not totally sure of, I'm not used to timing code):
 
My original version:  243 nanoseconds    17 lines of code
Erwin's version:       76 nanoseconds    42 lines of code
My second version:    111 nanoseconds    16 lines of code
My third version:      56 nanoseconds    52 lines of code
 
I'd appreciate it if someone would check this out and let me know if they find any bugs or anything.
GeneralRe: Yet another version - 25% faster, I think Pinmemberaleks1k21-Sep-11 2:47 
QuestionI used this function but I how I can catch variables from the * ??? Pinmembermoh.hijjawi20-Oct-09 1:55 
AnswerRe: I used this function but I how I can catch variables from the * ??? PinmemberRenniePet1-Apr-10 11:27 
Questionany updates ? Pinmemberalhambra-eidos2-Jul-09 5:12 
GeneralImproved matching with end-of-text PinmemberAnders Heie11-May-09 15:20 
GeneralRe: Improved matching with end-of-text: some cases don't work properly! Pinmemberroadrunner31412-Aug-09 3:35 
GeneralRe: Improved matching with end-of-text: some cases don't work properly! Pinmembersdiazdiaz20-Jun-13 1:50 
QuestionPathMatchSpec instead? Pinmemberkintz25-Mar-09 8:55 
AnswerRe: PathMatchSpec instead? PinmemberMandatoryDefault31-Aug-09 10:39 
Questionwchar_t version? Pinmemberrmorales8729-Nov-08 20:16 
AnswerRe: wchar_t version? Pinmemberrazvar31-Mar-11 21:49 

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