Base64的解码？

Question

为什么在Delphi6里提供Base64Encode函数而没有相关的解码函数。还是我没有找到，忘指教。

Answer 1

你可以用indy misc面板中的Idbase64Decoder控件来完成解码.

Answer 2

const
  //BaseTable
  BaseTable:string='ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
......
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;