Author: Tomas Rutkauskas

How to implement string pattern matching with wildcards

Answer:

There are many times when you need to compare two strings, but want to use wild 
cards in the match - all last names that begin with 'St', etc.

This function takes two strings and compares them. The first string can be 
anything, but should not contain pattern characters (* or ?). The pattern string 
can have as many of these pattern characters as you want. For example: 
MatchStrings('David Stidolph','*St*') would return True.}
1   
2   function MatchStrings(source, pattern: string): Boolean;
3   var
4     pSource: array[0..255] of Char;
5     pPattern: array[0..255] of Char;
6   
7     function MatchPattern(element, pattern: PChar): Boolean;
8   
9       function IsPatternWild(pattern: PChar): Boolean;
10      var
11        t: Integer;
12      begin
13        Result := StrScan(pattern, ' * ') <> nil;
14        if not Result then
15          Result := StrScan(pattern, ' ? ') <> nil;
16      end;
17  
18    begin
19      if 0 = StrComp(pattern, ' * ') then
20        Result := True
21      else if (element^ = Chr(0)) and (pattern^ <> Chr(0)) then
22        Result := False
23      else if element^ = Chr(0) then
24        Result := True
25      else
26      begin
27        case pattern^ of
28          ' * ':
29            if MatchPattern(element, @pattern[1]) then
30              Result := True
31            else
32              Result := MatchPattern(@element[1], pattern);
33          ' ? ':
34            Result := MatchPattern(@element[1], @pattern[1]);
35        else
36          if element^ = pattern^ then
37            Result := MatchPattern(@element[1], @pattern[1])
38          else
39            Result := False;
40        end;
41      end;
42    end;
43  
44  begin
45    StrPCopy(pSource, source);
46    StrPCopy(pPattern, pattern);
47    Result := MatchPattern(pSource, pPattern);
48  end;