unit1.~pas

Delphi写的base64算法程序

unit Unit1;

interface

uses
   Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;

type
   TForm1 = class(TForm)
    Edit1: TEdit;
    Edit2: TEdit;
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
   private
      { Private declarations }
   public
      { Public declarations }
   end;

const
   BaseTable: string = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';//BaseTable为BASE64码表
var
   Form1: TForm1;
function DecodeBase64(Source: string): string; //解码函数
function EncodeBase64(Source: string): string; //编码函数
function FindInTable(CSource:char):integer;  //
implementation

{$R *.DFM}

function FindInTable(CSource:char):integer;
begin
  result:=Pos(string(CSource),BaseTable)-1;
end;

function DecodeBase64(Source: string): string;
var
   SrcLen, Times, i: integer;
   x1, x2, x3, x4, xt: byte;
begin
   result := '';
   SrcLen := Length(Source);
   Times := SrcLen div 4;
   for i := 0 to Times - 1 do
      begin
         x1 := FindInTable(Source[1 + i * 4]);
         x2 := FindInTable(Source[2 + i * 4]);
         x3 := FindInTable(Source[3 + i * 4]);
         x4 := FindInTable(Source[4 + i * 4]);
         x1 := x1 shl 2;
         xt := x2 shr 4;
         x1 := x1 or xt;
         x2 := x2 shl 4;
         result := result + chr(x1);
         if x3 = 64 then break;
         xt := x3 shr 2;
         x2 := x2 or xt;
         x3 := x3 shl 6;
         result := result + chr(x2);
         if x4 = 64 then break;
         x3 := x3 or x4;
         result := result + chr(x3);
      end;
end;

function EncodeBase64(Source: string): string;
var
   Times, LenSrc, i: integer;
   x1, x2, x3, x4: char;
   xt: byte;
begin
   result := '';
   LenSrc := length(Source);
   if LenSrc mod 3 = 0 then
      Times := LenSrc div 3
   else
      Times := LenSrc div 3 + 1;
   for i := 0 to times - 1 do
      begin
         if LenSrc >= (3 + i * 3) then
            begin
               x1 := BaseTable[(ord(Source[1 + i * 3]) shr 2) + 1];
               xt := (ord(Source[1 + i * 3]) shl 4) and 48;
               xt := xt or (ord(Source[2 + i * 3]) shr 4);
               x2 := BaseTable[xt + 1];
               xt := (Ord(Source[2 + i * 3]) shl 2) and 60;
               xt := xt or (ord(Source[3 + i * 3]) shr 6);
               x3 := BaseTable[xt + 1];
               xt := (ord(Source[3 + i * 3]) and 63);
               x4 := BaseTable[xt + 1];
            end
         else
            if LenSrc >= (2 + i * 3) then
            begin
               x1 := BaseTable[(ord(Source[1 + i * 3]) shr 2) + 1];
               xt := (ord(Source[1 + i * 3]) shl 4) and 48;
               xt := xt or (ord(Source[2 + i * 3]) shr 4);
               x2 := BaseTable[xt + 1];
               xt := (ord(Source[2 + i * 3]) shl 2) and 60;
               x3 := BaseTable[xt + 1];
               x4 := '=';
            end
         else
            begin
               x1 := BaseTable[(ord(Source[1 + i * 3]) shr 2) + 1];
               xt := (ord(Source[1 + i * 3]) shl 4) and 48;
               x2 := BaseTable[xt + 1];
               x3 := '=';
               x4 := '=';
            end;
         result := result + x1 + x2 + x3 + x4;
      end;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
edit2.Text:=EncodeBase64(edit1.Text);
end;

end.