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Wildcard Manipulation for Text

, 18 May 2005
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Searches and replaces text based on a pattern that uses wildcards.

Sample Image - diskinfo.png

Introduction

Sometimes it is handy to have an utility that will search for a certain text pattern or execute a find and replace based on it. The string provides some limited ability to do that, but you are out of luck if you need these functions to be case insensitive and to use a wildcard algorithm.

Background

The tradeoff for this situation is that, you cannot look for ‘*’ and ‘?’ in your target text. But that’s what the string is good for, isn’t it!

I’ve included a solution with two projects. The DLL has the code that implements algorithm and the executable is merely a client that would let you enjoy the functionality in a visual way. Here is the code that's the heart for this algorithm.

protected bool _PatternMatched(int IndexText, int IndexPattern)
{            
  while (true)
  {
    char CrtTxtChar, CrtPatternChar;
    CrtPatternChar= 
      (IndexPattern == patternlen)?'*':ConvertCase(strpattern[IndexPattern++]);
    switch (CrtPatternChar )
    {
      case '*':
        if(IndexPattern == patternlen)//last *, used by FindPatternPosition
        {
          this.last = IndexText;
          return true;// last pattern char == *, no need to check the last chars
        }
        while (IndexText < txtlen)
        {               
          if(_PatternMatched(IndexText++,IndexPattern))
          {
            return true;
          }
        }
        return false;
        break;
      case '?':
        if(IndexText == txtlen)
          return false;
        IndexText++;
        break;
      default:
        if(IndexText == txtlen)
          CrtTxtChar = '\0';
        else
          CrtTxtChar = ConvertCase( strtxt[IndexText++] );
        if( CrtTxtChar != CrtPatternChar )  // check for exact char
        {
          if(CrtTxtChar=='\0')
            return false;
          else if(_PatternMatched(IndexText, 0))
          {
            if(this.first < IndexText)
              this.first = IndexText;
            return true;
          }
          else
            return false;
        }
        else
        {
          if(this.last < IndexText -1)
            this.last = IndexText -1;
        }
        break;
    }//switch ends
  }//while ends
}//_PatternMatched ends

This protected method is used by the public methods IsPatternMatch and ReplaceTextEx that are exposed by this class. The first and last data members store the position of the pattern in the target string in order to allow the replace to work.

Using the code

Just instantiate a class of WildCardTxtUtility and call its public functions.

Beware

A large target text and multiple wildcards in the pattern will cause performance issues. I would welcome any attempt to address them.

History

  • This is version 1.0.

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

dmihailescu
Software Developer (Senior)
United States United States
Decebal Mihailescu is a software engineer with interest in .Net, C# and C++.

Comments and Discussions

 
Generalbug report PinmemberTiger.xing8-Dec-05 18:42 
GeneralRe: bug report Pinmemberdmihailescu7-Feb-07 5:30 
Generalanother bug fix Pinmemberdmihailescu8-Feb-07 4:21 
GeneralRegular Expressions PinmemberEric Woodruff18-May-05 16:22 
GeneralRe: Regular Expressions PinsitebuilderUwe Keim18-May-05 18:39 
GeneralI did not know about them Pinmemberdmihailescu19-May-05 2:57 
GeneralRe: Regular Expressions Pinmemberzwir31-Jul-07 22:40 

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