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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Well, as direct as I could come up with anyway. Makes use of unsafe to enable pointer arithmetic. Unfortunately, because fixed is required to prevent the GC from moving the pointers, I had to change it to use increment indexers instead of directly manipulating the pointers. Alternatively, you could use stackalloc to instantiate two native char[]'s and copy the values, but that seems contrary to this function's low-memory footprint, high performance goals.

Has been tested against every test case presented in the comments section as well as some additional cases I threw in.

public unsafe static bool GlobCompare( string glob, string path )
{
      fixed ( char* pGlob = glob, pPath = path )
      {
            int pGlobInc = 0;
            int pPathInc = 0;

            int mp = 0;
            int cp = 0;

            while ( ( *( pPath + pPathInc ) != 0 ) && ( *( pGlob + pGlobInc ) != '*' ) )
            {
                  if ( ( *( pGlob + pGlobInc ) != *( pPath + pPathInc ) ) && ( *( pGlob + pGlobInc ) != '?' ) )
                  {
                        return false;
                  }
                  pGlobInc++;
                  pPathInc++;
            }

            while ( *( pPath + pPathInc ) != 0 )
            {
                  if ( *( pGlob + pGlobInc ) == '*' )
                  {
                        if ( 0 == *( pGlob + ++pGlobInc ) )
                        {
                              return true;
                        }
                        mp = pGlobInc;
                        cp = pPathInc + 1;
                  }
                  else if ( ( *( pGlob + pGlobInc ) == *( pPath + pPathInc ) ) || ( *( pGlob + pGlobInc ) == '?' ) )
                  {
                        pGlobInc++;
                        pPathInc++;
                  }
                  else
                  {
                        pGlobInc = mp;
                        pPathInc = cp++;
                  }
            }

            while ( *( pGlob + pGlobInc ) == '*' )
            {
                  pGlobInc++;
            }
            return ( 0 == *( pGlob + pGlobInc ) );
      }
}

public static bool WildcardMatch(string strCompare, string strWild, bool bIgnoreCase)
{
    if (bIgnoreCase)
    {
        strWild = strWild.ToUpper();
        strCompare = strCompare.ToUpper();
    }
 
    // Lengths of strings
    int iWildLen = strWild.Length;
    int iCompareLen = strCompare.Length;
 
    // Used to save position when '*' found in strWild
    // Initialized to invalid values
    int iWildMatched = iWildLen;
    int iCompareBase = iCompareLen;
 
    int iWild = 0;
    int iCompare = 0;
 
    // Match until first wildcard '*'
    while (iCompare < iCompareLen && (iWild >= iWildLen || strWild[iWild] != '*'))
    {
        if (iWild >= iWildLen || (strWild[iWild] != strCompare[iCompare] && strWild[iWild] != '?'))
            return false;
 
        iWild++;
        iCompare++;
    }
 
    // Process wildcard
    while (iCompare < iCompareLen)
    {
        if (iWild < iWildLen)
        {
            if (strWild[iWild] == '*')
            {
                iWild++;
 
                if (iWild == iWildLen)
                    return true;
 
                iWildMatched = iWild;
                iCompareBase = iCompare + 1;
 
                continue;
            }
 
            if (strWild[iWild] == strCompare[iCompare] || strWild[iWild] == '?')
            {
                iWild++;
                iCompare++;
 
                continue;
            }
        }
 
        iWild = iWildMatched;
        iCompare = iCompareBase++;
    }
 
    while (iWild < iWildLen && strWild[iWild] == '*')
        iWild++;
 
    if (iWild < iWildLen)
        return false;
 
    return true;
}