Code:

function PretrazivanjeFajla(strFileName: string;
  strStaSeTrazi: widestring; intModPretrazivanje: integer): Boolean;
const
  BufferSize= $8001;  { 32K+1 bytes }

var
  pBuf, pEnd, pScan, pPos : Pchar;
  lintFileSize: LongInt;
  lintBytesRemaining: LongInt;
  intBytesToRead: Integer;
  fileTemp: File;
  intoldMode: Word;
  strTemp: wideString;
  arrstrSearchFor:  array of
                            Record
                              pcSearchFor: PChar;
                              blnFound: boolean;
                            end;
  intBrojac: integer;
  blnPrekid01: Boolean;
begin



  if (Length( strStaSeTrazi ) = 0) or (Length( strFileName ) = 0) then
    Exit;
  pBuf      := nil;


  AssignFile(fileTemp, strFileName);
  intoldMode := FileMode;
  FileMode := 0;
  Reset(fileTemp, 1);
  FileMode := intoldMode;

  strTemp:=WideUpperCase(strStaSeTrazi);
  strTemp:=StringReplace(strTemp,#200,'Č',[rfReplaceAll]);
  strTemp:=StringReplace(strTemp,#208,'Đ',[rfReplaceAll]);
  strTemp:=StringReplace(strTemp,#198,'Ć',[rfReplaceAll]);
  strStaSeTrazi:=strTemp;

  try
    SetLength(arrstrSearchFor, 0);
    if intModPretrazivanje=0 then
      begin
        SetLength(arrstrSearchFor, Length(arrstrSearchFor)+1);
        arrstrSearchFor[Length(arrstrSearchFor)-1].pcSearchFor:=StrAlloc(Length(strStaSeTrazi)+1);
        StrPCopy(arrstrSearchFor[Length(arrstrSearchFor)-1].pcSearchFor, strStaSeTrazi);
        arrstrSearchFor[length(arrstrSearchFor)-1].blnFound:=false;
      end
    else
      begin
        while Length(strStaSeTrazi)>0 do
          begin
            if Pos(' ', strStaSeTrazi)>0 then
              begin
                strTemp:=Copy(strStaSeTrazi, 1, Pos(' ', strStaSeTrazi) - 1);
                Delete(strStaSeTrazi, 1, Pos(' ', strStaSeTrazi));
              end
            else
              begin
                strTemp:=strStaSeTrazi;
                Delete(strStaSeTrazi, 1, 255);
              end;

            if Length(strStaSeTrazi)>0 then
              begin
                while (strStaSeTrazi[1]=' ') do
                  begin
                    Delete(strStaSeTrazi, 1, 1);
                    if Length(strStaSeTrazi)=0 then
                      break;
                  end;
              end;
            SetLength(arrstrSearchFor, Length(arrstrSearchFor)+1);


            arrstrSearchFor[Length(arrstrSearchFor)-1].pcSearchFor:=StrAlloc(Length(strTemp)+1);
            StrPCopy(arrstrSearchFor[Length(arrstrSearchFor)-1].pcSearchFor, strTemp);
            arrstrSearchFor[length(arrstrSearchFor)-1].blnFound:=false;
          end;
      end;

    GetMem(pBuf, BufferSize);
    lintFileSize := System.Filesize(fileTemp);
    lintBytesRemaining := lintFileSize;
    pPos := nil;


    while lintBytesRemaining > 0 do
      begin
        if lintbytesRemaining >= BufferSize then
          intBytesToRead := Pred(BufferSize)
        else
          intBytesToRead := lintBytesRemaining;

        BlockRead(fileTemp, pBuf^, intBytesToRead, intBytesToRead);
        pEnd := @pBuf[intBytesToRead];
        pEnd^:= #0;

        pScan := pBuf;
        while pScan < pEnd do
          begin
            AnsiUpper(pScan);

            strTemp:=pScan;

            strTemp:=StringReplace(strTemp,'&#269;','&#268;', [rfReplaceAll]);
            strTemp:=StringReplace(strTemp,'&#273;','&#272;', [rfReplaceAll]);
            strTemp:=StringReplace(strTemp,'&#263;','&#262;', [rfReplaceAll]);
            strTemp:=StringReplace(strTemp,char(13)+char(10),' ', [rfReplaceAll]);
            strTemp:=StringReplace(strTemp,'  ',' ', [rfReplaceAll]);

            StrPCopy(pScan, strTemp);

             for intBrojac:=0 to Length(arrstrSearchFor)-1 do
              begin
                pPos := StrPos(pScan, arrstrSearchFor[intBrojac].pcSearchFor);
                if pPos <> nil then
                  begin
                    arrstrSearchFor[intBrojac].blnFound:=True;
                    blnPrekid01 := ((intModPretrazivanje=0) or (intModPretrazivanje=1)) and true
                  end;

                if blnPrekid01 then
                  break;

              end;


            pScan := StrEnd(pScan);
            Inc(pScan);
          end;

      if blnPrekid01 then
        Break;
      lintBytesRemaining := lintBytesRemaining - intBytesToRead;
      if lintBytesRemaining > 0 then
        begin
          Seek(fileTemp, FilePos(fileTemp)-Length(strStaSeTrazi));
          lintBytesRemaining := lintBytesRemaining + Length(strStaSeTrazi);
        end;
      end;
    finally
      CloseFile(fileTemp);

      if blnPrekid01 then
        Result:=true;
      if intModPretrazivanje=2 then
        begin
          Result:=True;
          for intBrojac:=0 to Length(arrstrSearchFor)-1 do
            begin
              Result:=Result and arrstrSearchFor[intBrojac].blnFound;
            end;
        end;

      for intBrojac:=0 to Length(arrstrSearchFor)-1 do
        begin
          if arrstrSearchFor[intBrojac].pcSearchFor <> nil then
            StrDispose(arrstrSearchFor[intBrojac].pcSearchFor);
        end;
      SetLength(arrstrSearchFor, 0);
      If pBuf <> nil then
        FreeMem(pBuf, BufferSize);
    end;
end;