Is There An Efficient Whole Word Search Function in Delphi?

Question

In Delphi 2009 or later (Unicode), are there any built-in functions or small routines written somewhere that will do a reasonably efficient whole word search where you provi

Answer 1

Just because Delphi's editor has a "word match" function, that doesn't mean the Delphi library offers it!

Typically, in most languages the way to go for this is a regular expression. Seems they're (still) not built into Delphi, as there are 3rd party libraries offering the capability. The first example I found is: http://delphi.about.com/od/toppicks/tp/delphi-regular-expressions.htm .

Typically, you'd build a regular expression something like

myRegex = '[' + Delim + ']+' + Word + '[' + Delim + ']+';
if regexSearch (Str, myRegex) then ...

You'll want to get details from the documentation of the library you get. My example doesn't correctly handle the case of the word starting at the beginning of Str or ending at its end, or being all of Str.

Answer 2

If you have function like below

function ExistWordInString(aString:PWideChar;aSearchString:string;aSearchOptions: TStringSearchOptions): Boolean;
var
  Size : Integer;
Begin
      Size:=StrLen(aString);
      Result := SearchBuf(aString, Size, 0, 0, aSearchString, aSearchOptions)<>nil;
End;

and call it like this:

ExistWordInString('Go Delphi Go','Delphi',[soWholeWord,soDown]);

You may not fell any problem if you call it once. But if you call this in a loop (for example 1000 times or more) first using Pos function (like below) will surprisingly give you extra performance

function ExistWordInString(const AString:string;const ASearchString:string;ASearchOptions: TStringSearchOptions): Boolean;
var
  Size : Integer;
  AWChar: PWideChar;
begin
   if Pos(LowerCase(ASearchString), LowerCase(AString)) = 0 then
   begin
      Exit(False);
   end;

   AWChar := PWideChar(AString);
   Size:=StrLen(AWChar);
   Result := SearchBuf(AWChar, Size, 0, 0, ASearchString, ASearchOptions)<>nil;
end;

Answer 3

This function is not exactly what you need but it is pretty close:

I hope it is useful:

{ Copy all whole words from MainStr. The result will not have more than MaxChars characters. }

function CopyWords(MainStr: string; MaxChars: Integer): string;   
VAR EndsInSpace: Boolean;
    EndString, i: Integer;
    NextChar: char;
begin
 Assert(MaxChars > 0);
 EndString:= MaxChars;

 if Length(MainStr) > MaxChars then
  begin
   NextChar:= mainstr[MaxChars+1];

   if (MainStr[MaxChars] <> ' ') AND (NextChar <> ' ')
   then
     begin
      for i:= MaxChars downto 1 DO
       if MainStr[i]= ' ' then
        begin
         EndString:= i;
         Break;
        end
     end
   else
    if (MainStr[MaxChars]  = ' ')
    OR (MainStr[MaxChars] <> ' ') AND (NextChar = ' ')
    then EndString:= MaxChars;
  end;

 Result:= CopyTo(MainStr, 1, EndString);
 Result:= TrimRight(Result);
end;

Answer 4

You can use the SearchBuf function with the [soWholeWord] option.

function SearchBuf(Buf: PAnsiChar; BufLen: Integer; SelStart: Integer; SelLength: Integer; SearchString: AnsiString; Options: TStringSearchOptions): PAnsiChar;

See this example

function ExistWordInString(aString:PWideChar;aSearchString:string;aSearchOptions: TStringSearchOptions): Boolean;
var
  Size : Integer;
Begin
      Size:=StrLen(aString);
      Result := SearchBuf(aString, Size, 0, 0, aSearchString, aSearchOptions)<>nil;
End;

Use it this way

ExistWordInString('Go Delphi Go','Delphi',[soWholeWord,soDown]);

Bye.