Система перестановок

unit Unit1;

interface

uses

Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

Dialogs, StdCtrls, ComCtrls, Menus;

type

TForm1 = class(TForm)

real_str: TEdit;

Button1: TButton;

Label1: TLabel;

Label2: TLabel;

Label3: TLabel;

Button2: TButton;

smeshch: TEdit;

Label4: TLabel;

Memo1: TMemo;

decr_str: TEdit;

procedure Button1Click(Sender: TObject);

procedure smeshchChange(Sender: TObject; var knopka: Char);

procedure Button2Click(Sender: TObject);

procedure FormActivate(Sender: TObject);

private

{ Private declarations }

public

{ Public declarations }

end;

var

Form1: TForm1;

dlina: integer;

implementation

{$R *.dfm}

procedur TForm1.Button1Click(Sender: TObject); //telo procedury

var //obъyavlenie peremennyh

stroka: string;

massiv: array of integer;

i: integer;

begin

memo1.lines.Clear; //ochistka polya dlya zashifrovannoi stroki

stroka:= real_str.text; //poluchenie real'noi sroki

dlina:= length(stroka); //uznati dlinu stroki i zapisat' v dlina

setlength(stroka, dlina+1); //zadat' dlinu

setlength(massiv, dlina+1);

if real_str.text = '' then //proverka na pustotu polya. esli pusto, to soobshenie, focus na obъekte i vihod iz procedury

begin

ShowMessage('Введите шифруемую строку');

real_str.SetFocus;

exit; end;

if smeshch.text = '' then // to zhe samoe

begin

button2.Enabled:= false;

ShowMessage('Введите смещение');

smeshch.SetFocus;

exit; end;

if StrToInt(smeshch.text) > 256 then //potomu chto vsego byvaet 256 ASCII simvolov

begin

button2.Enabled:= false;

showmessage('Смещение не может быть больше 256');

smeshch.text:= '0';

smeshch.SetFocus;

end

else begin

for i:= 1 to dlina do

begin

massiv[i]:= ord(stroka[i]) + StrToInt(smeshch.text);

if massiv[i] > 255 then

massiv[i]:= massiv[i] mod 256 // ostatok ot deleniya na 256

end; end;

for i:= 1 to dlina do

begin

memo1.Lines[0]:= memo1.Lines[0] + chr(massiv[i]);

end;

button2.Enabled:= true;

button2.SetFocus;

decr_str.Text:= '';

end;

procedure TForm1.smeshchChange(Sender: TObject; var knopka: Char); //telo pocedury. zapreshaet vvod lyubyj simvolov, krome 0-9

begin

case knopka of

'0'..'9', #8:

else knopka:= #0;

end;end;

procedure TForm1.Button2Click(Sender: TObject);

var

decr_sym: char;

i: integer;

begin

button2.Enabled:= false;

decr_str.Text:= '';

for i:= 1 to dlina do

begin

if (ord(memo1.Lines[0][i]) - StrToInt(smeshch.text)) >= 0 then

begin

decr_sym:= chr(ord(memo1.Lines[0][i]) - StrToInt(smeshch.text));

decr_str.Text:= decr_str.Text + decr_sym;

end

else begin

decr_sym:= chr(256 - (StrToInt(smeshch.Text) - ord(memo1.Lines[0][i])));

decr_str.Text:= decr_str.Text + decr_sym;

end; end;end;

procedure TForm1.FormActivate(Sender: TObject);

begin

button2.Enabled:= false;

real_str.SetFocus;

end;end.