string与base64编码转换.txt

大量Delphi开发资料

function Base64ToString(const Value : string): string;
var
 x, y, n, l: Integer;
 d: array[0..3] of Byte;
 Table : string;
begin
 Table :=
   #$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$3E +#$40
   +#$40 +#$40 +#$3F +#$34 +#$35 +#$36 +#$37 +#$38 +#$39 +#$3A +#$3B +#$3C
   +#$3D +#$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$40 +#$00 +#$01 +#$02 +#$03
   +#$04 +#$05 +#$06 +#$07 +#$08 +#$09 +#$0A +#$0B +#$0C +#$0D +#$0E +#$0F
   +#$10 +#$11 +#$12 +#$13 +#$14 +#$15 +#$16 +#$17 +#$18 +#$19 +#$40 +#$40
   +#$40 +#$40 +#$40 +#$40 +#$1A +#$1B +#$1C +#$1D +#$1E +#$1F +#$20 +#$21
   +#$22 +#$23 +#$24 +#$25 +#$26 +#$27 +#$28 +#$29 +#$2A +#$2B +#$2C +#$2D
   +#$2E +#$2F +#$30 +#$31 +#$32 +#$33 +#$40 +#$40 +#$40 +#$40 +#$40 +#$40;

 SetLength(Result, Length(Value));
 x := 1;
 l := 1;
 while x < Length(Value) do
 begin
   for n := 0 to 3 do
   begin
     if x > Length(Value) then
       d[n] := 64
     else
     begin
       y := Ord(Value[x]);
       if (y < 33) or (y > 127) then
         d[n] := 64
       else
         d[n] := Ord(Table[y - 32]);
     end;
     Inc(x);
   end;
   Result[l] := Char((D[0] and $3F) shl 2 + (D[1] and $30) shr 4);
   Inc(l);
   if d[2] <> 64 then
   begin
     Result[l] := Char((D[1] and $0F) shl 4 + (D[2] and $3C) shr 2);
     Inc(l);
     if d[3] <> 64 then
     begin
       Result[l] := Char((D[2] and $03) shl 6 + (D[3] and $3F));
       Inc(l);
     end;
   end;
 end;
 Dec(l);
 SetLength(Result, l);
end;

function StringToBase64(const Value: string): string;
var
 c: Byte;
 n, l: Integer;
 Count: Integer;
 DOut: array[0..3] of Byte;
 Table : string;
begin
 Table :=
   'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

 setlength(Result, ((Length(Value) + 2) div 3) * 4);
 l := 1;
 Count := 1;
 while Count <= Length(Value) do
 begin
   c := Ord(Value[Count]);
   Inc(Count);
   DOut[0] := (c and $FC) shr 2;
   DOut[1] := (c and $03) shl 4;
   if Count <= Length(Value) then
   begin
     c := Ord(Value[Count]);
     Inc(Count);
     DOut[1] := DOut[1] + (c and $F0) shr 4;
     DOut[2] := (c and $0F) shl 2;
     if Count <= Length(Value) then
     begin
       c := Ord(Value[Count]);
       Inc(Count);
       DOut[2] := DOut[2] + (c and $C0) shr 6;
       DOut[3] := (c and $3F);
     end
     else
     begin
       DOut[3] := $40;
     end;
   end
   else
   begin
     DOut[2] := $40;
     DOut[3] := $40;
   end;
   for n := 0 to 3 do
   begin
     Result[l] := Table[DOut[n] + 1];
     Inc(l);
   end;
 end;
end;

function GetTitle(const Value: string): string;
var
 iPos: integer;
begin
 Result := Value;
 if Copy(Value, 1, 2) <> '=?' then exit;
 //'?B?'前面的都要去掉
 iPos := Pos('?B?', Value);
 Inc(iPos, 3);
 //最后的'?='也要去掉
 Result := Copy(Value, iPos, Length(Value) - iPos - 1);
 Result := Base64ToString(Result);
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
 ShowMessage(GetTitle('=?gb2312?B?YXNkZnNhZGZkc2Fm1tC5+g==?='));
end;

end.