字符转换为Base64编码

字符转换为Base64编码

function strtoBase64(str:string):string;
var
  _1byte,_2byte:array of byte;
  strlen,i,j,jj:integer;
const
  basetable='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/';
begin
  //str:='xxc';
//str:='abcabc';
  strlen:=length(str);
  setlength(_1byte,strlen);
  if strlen mod 3 >0 then setlength(_2byte,((strlen div 3) * 4 + strlen mod 3)+1)
  else setlength(_2byte,(strlen div 3)*4+(strlen mod 3)+0);

  for i:=0 to strlen-1 do
  begin
    _1byte[i]:=ord(str[i+1]);
  end;
  j:=0;
  jj:=0;
  for i:=0 to (strlen div 3)-1 do
  begin
    j:=i*3;
    _2byte[jj]:=_1byte[j] shr(2); //a->A;
    inc(jj);
    _2byte[jj]:=byte(_1byte[j] shl(6)) shr(2) + _1byte[j+1] shr(4); //a&b->B
    inc(jj);
    _2byte[jj]:=byte(_1byte[j+1] shl(4)) shr(2)+_1byte[j+2]shr(6); //b&c->C
    inc(jj);
    _2byte[jj]:=byte(_1byte[j+2] shl(2))shr(2);
    inc(jj);
  end;
  j:=(strlen div 3)*3;
  case (strlen mod 3) of
    1:
    begin
       _2byte[jj]:=_1byte[j] shr(2); //a->A;
       inc(jj);
       _2byte[jj]:=byte(_1byte[j] shl(6)) shr(2); //a&b->B
    end;
    2:
    begin
       _2byte[jj]:=_1byte[j] shr(2); //a->A;
       inc(jj);
       _2byte[jj]:=byte(_1byte[j] shl(6)) shr(2) + _1byte[j+1] shr(4); //a&b->B
       inc(jj);
       _2byte[jj]:=byte(_1byte[j+1] shl(4)) shr(2); //b2->C
    end;
  end;
//按照编码显示！
  str:='';
  for i:=0 to high(_2byte) do
  begin
    str:=str+copy(basetable,_2byte[i]+1,1);
  end;

  Result := str;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
   edit2.Text := strtoBase64(edit1.Text);
end;