-- Base64 encode/decode & test driver.
-- Copyright 2001 Tom Moran (tmoran@acm.org, PGP signed tmoran@bix.com),
-- anyone may use for any purpose.
with Ada.Streams;
package Base64 is
-- RFC 1521, MIME Base64 encode/decode
-- Assumes Ada.Streams.Stream_Element is a byte.
procedure Decode(Source : in String;
Target : out Ada.Streams.Stream_Element_Array;
Last : out Ada.Streams.Stream_Element_Offset);
-- decode Source into Target(Target'first .. Last)
-- Note: it may be appropriate to prescan Source for '=',
-- indicating termination, or for illegitimate characters,
-- indicating corruption, before calling Decode.
procedure Encode(Source : in Ada.Streams.Stream_Element_Array;
Target : out String;
Last : out Natural);
-- Target is filled in four character increments, except that
-- a CR-LF pair is inserted after every 76 characters.
-- Target'length must be at least:
-- Output_Quad_Count: constant := (Source'length + 2) / 3;
-- Output_Byte_Count: constant := 4 * Output_Quad_Count;
-- Target'length = Output_Byte_Count + 2 * (Output_Byte_Count / 76)
-- Constraint_Error will be raised if Target isn't long enough.
end Base64;
with Ada.Streams;
package body Base64 is
subtype Six_Bits is Ada.Streams.Stream_Element range 0 .. 63;
From_String: constant array (Character) of Six_Bits
:= ('A' => 0,'B' => 1,'C' => 2,'D' => 3,'E' => 4,'F' => 5,'G' => 6,
'H' => 7,'I' => 8,'J' => 9,'K' =>10,'L' =>11,'M' =>12,'N' =>13,
'O' =>14,'P' =>15,'Q' =>16,'R' =>17,'S' =>18,'T' =>19,'U' =>20,
'V' =>21,'W' =>22,'X' =>23,'Y' =>24,'Z' =>25,'a' =>26,'b' =>27,
'c' =>28,'d' =>29,'e' =>30,'f' =>31,'g' =>32,'h' =>33,'i' =>34,
'j' =>35,'k' =>36,'l' =>37,'m' =>38,'n' =>39,'o' =>40,'p' =>41,
'q' =>42,'r' =>43,'s' =>44,'t' =>45,'u' =>46,'v' =>47,'w' =>48,
'x' =>49,'y' =>50,'z' =>51,'0' =>52,'1' =>53,'2' =>54,'3' =>55,
'4' =>56,'5' =>57,'6' =>58,'7' =>59,'8' =>60,'9' =>61,'+' =>62,
'/' =>63,
others => 0);
procedure Decode(Source : in String;
Target : out Ada.Streams.Stream_Element_Array;
Last : out Ada.Streams.Stream_Element_Offset) is
-- decode Source into Target(Target'first .. Last)
-- Note: it may be appropriate to prescan Source for '=',
-- indicating termination, or for illegitimate characters,
-- indicating corruption, before calling Decode.
use type Ada.Streams.Stream_Element;
use type Ada.Streams.Stream_Element_Offset;
D : Six_Bits;
type Slots is mod 4;
Slot : Slots := 0;
begin
Last := Target'first - 1;
for Si in Source'range loop
D := From_String(Source(Si));
if D /= 0 or else Source(Si) = 'A' then
-- OK source
case Slot is
when 0 =>
Last := Last + 1;
Target(Last) := 4 * D; -- dddddd00 ........ ........
when 1 =>
Target(Last) := Target(Last) + D / 16;
exit when Last = Target'last
and then (Si = Source'last or else Source(Si + 1) = '=')
and then (D mod 16) = 0;
Last := Last + 1;
Target(Last) := (D mod 16) * 16; -- dddddddd dddd0000 ........
when 2 =>
Target(Last) := Target(Last) + D / 4;
exit when Last = Target'last
and then (Si = Source'last or else Source(Si + 1) = '=')
and then (D mod 4) = 0;
Last := Last + 1;
Target(Last) := (D mod 4) * 64; -- dddddddd dddddddd dd000000
when 3 =>
Target(Last) := Target(Last) + D; -- dddddddd dddddddd dddddddd
end case;
Slot := Slot + 1;
elsif Source(Si) = '=' then
exit; -- terminator encountered
end if; -- silently ignore whitespace, lf, garbage, ...
end loop;
end Decode;
To_String: constant array (Six_Bits) of Character
:= "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
procedure Encode(Source : in Ada.Streams.Stream_Element_Array;
Target : out String;
Last : out Natural) is
-- Target is filled in four character increments, except that
-- a CR-LF pair is inserted after every 76 characters.
-- Target'length must be at least:
-- Output_Quad_Count: constant := (Source'length + 2) / 3;
-- Output_Byte_Count: constant := 4 * Output_Quad_Count;
-- Target'length = Output_Byte_Count + 2 * (Output_Byte_Count / 76)
-- Constraint_Error will be raised if Target isn't long enough.
use type Ada.Streams.Stream_Element;
use type Ada.Streams.Stream_Element_Offset;
D : Six_Bits;
type Slots is mod 3;
Slot : Slots := 0;
Output_Line_Length: Natural := 0;
begin
Last := Target'first - 1;
for Si in Source'range loop
case Slot is
when 0 =>
if Output_Line_Length = 76 then
Last := Last + 2;
Target(Last - 1) := Ascii.Cr;
Target(Last) := Ascii.Lf;
Output_Line_Length := 0;
end if;
Output_Line_Length := Output_Line_Length + 4;
Last := Last + 4;
Target(Last - 3) := To_String(Source(Si) / 4);
D := (Source(Si) mod 4) * 16;
Target(Last - 2) := To_String(D);
Target(Last - 1) := '=';
Target(Last) := '=';
-- dddddd dd0000 = =
when 1 =>
D := D + Source(Si) / 16;
Target(Last - 2) := To_String(D);
D := (Source(Si) mod 16) * 4;
Target(Last - 1) := To_String(D);
-- dddddd dddddd dddd00 =
when 2 =>
D := D + Source(Si) / 64;
Target(Last - 1) := To_String(D);
Target(Last) := To_String(Source(Si) mod 64);
-- dddddd dddddd dddddd dddddd
end case;
Slot := Slot + 1;
end loop;
end Encode;
end Base64;
with Base64,
Ada.Streams,
Ada.Streams.Stream_Io,
Ada.Text_Io;
use Ada.Streams;
procedure Test64 is
-- read N bytes from file "a", encode, decode, and see if original restored
procedure Test(N : in Stream_Element_Offset) is
Fd : Stream_Io.File_Type;
Output_Quad_Count: constant Integer := (Integer(N) + 2) / 3;
Output_Byte_Count: constant Integer := 4 * Output_Quad_Count;
Encoded : String(1 .. Output_Byte_Count + 2 * (Output_Byte_Count / 76));
Last_E : Integer;
Buffer,
Buffer2 : Stream_Element_Array(1 .. N);
Last_D : Stream_Element_Offset;
begin
Ada.Text_Io.Put_Line("test" & Stream_Element_Offset'Image(N));
Stream_Io.Open(Fd, Stream_Io.In_File, "a");
Stream_Io.Read(Fd, Buffer, Last_D);
Base64.Encode(Buffer(1 .. Last_D), Encoded, Last_E);
Ada.Text_Io.Put_Line("encoded in" & Integer'Image(Last_E));
Ada.Text_Io.Put(Encoded(1 .. Last_E));
Ada.Text_Io.New_Line;
Base64.Decode(Encoded(1 .. Last_E), Buffer2, Last_D);
if Last_D /= Buffer2'last then
Ada.Text_Io.Put_Line(Stream_Element_Offset'Image(Last_D)
& "/="
& Stream_Element_Offset'Image(Buffer2'last));
end if;
if Buffer2(1 .. Last_D) /= Buffer then
Ada.Text_Io.Put_Line("/=");
end if;
Stream_Io.Close(Fd);
end Test;
begin
for I in Stream_Element_Offset range 9 .. 14 loop
Test(I);
end loop;
for I in Stream_Element_Offset range 252 .. 290 loop
Test(I);
end loop;
for I in Stream_Element_Offset range 1 .. 9 loop
Test(I);
end loop;
end Test64;
|
