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439 | -----------------------------------------------------------------------
-- util-encoders-base32 -- Encode/Decode a stream in Base32
-- Copyright (C) 2023 Stephane Carrez
-- Written by Stephane Carrez (Stephane.Carrez@gmail.com)
--
-- Licensed under the Apache License, Version 2.0 (the "License");
-- you may not use this file except in compliance with the License.
-- You may obtain a copy of the License at
--
-- http://www.apache.org/licenses/LICENSE-2.0
--
-- Unless required by applicable law or agreed to in writing, software
-- distributed under the License is distributed on an "AS IS" BASIS,
-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-- See the License for the specific language governing permissions and
-- limitations under the License.
-----------------------------------------------------------------------
package body Util.Encoders.Base32 is
use Interfaces;
-- ------------------------------
-- Encodes the binary input stream represented by `Data` into
-- the a base32 output stream `Into`.
--
-- If the transformer does not have enough room to write the result,
-- it must return in `Encoded` the index of the last encoded
-- position in the `Data` stream.
--
-- The transformer returns in `Last` the last valid position
-- in the output stream `Into`.
--
-- The `Encoding_Error` exception is raised if the input
-- stream cannot be transformed.
-- ------------------------------
overriding
procedure Transform (E : in out Encoder;
Data : in Ada.Streams.Stream_Element_Array;
Into : out Ada.Streams.Stream_Element_Array;
Last : out Ada.Streams.Stream_Element_Offset;
Encoded : out Ada.Streams.Stream_Element_Offset) is
-- Get 5 bytes generates 8 bytes
-- C C-1
-- 0: { 5.0 } 0x1F rshift 3 0x0
-- 1: { 3.0 + 2.1} 0x03 rshift 6 0x1C lshift 2
-- 2: { 5.1 } 0x1F lshift 1
-- 3: { 1.1 + 4.2} 0x0F lshift 4 0x10 rshift 4
-- 4: { 4.2 + 1.3} 0x01 lshift 7 0x1E rshift 1
-- 5: { 5.3 } 0x1F lshift 2
-- 6: { 2.3 + 3.4} 0x07 lshift 5 0x18 rshift 3
-- 7: { 5.4 } 0x1F rshift 0
Pos : Ada.Streams.Stream_Element_Offset := Into'First;
I : Ada.Streams.Stream_Element_Offset := Data'First;
C : Unsigned_8;
Alphabet : constant Alphabet_Access := E.Alphabet;
R : Unsigned_8 := E.Remain;
State : Encode_State_Type := E.State;
begin
while Pos <= Into'Last loop
case State is
when 0 =>
exit when I > Data'Last;
State := 1;
C := Unsigned_8 (Data (I));
Into (Pos) := Alphabet (Shift_Right (C, 3));
R := Shift_Left (C, 2) and 16#1C#;
Pos := Pos + 1;
I := I + 1;
when 1 =>
exit when I > Data'Last;
State := 2;
C := Unsigned_8 (Data (I));
Into (Pos) := Alphabet (Shift_Right (C and 16#C0#, 6) or R);
R := C;
Pos := Pos + 1;
I := I + 1;
when 2 =>
State := 3;
Into (Pos) := Alphabet (Shift_Right (R and 16#3E#, 1));
R := Shift_Left (R, 4) and 16#10#;
Pos := Pos + 1;
when 3 =>
exit when I > Data'Last;
State := 4;
C := Unsigned_8 (Data (I));
Into (Pos) := Alphabet (Shift_Right (C and 16#F0#, 4) or R);
R := Shift_Left (C, 1) and 16#1E#;
Pos := Pos + 1;
I := I + 1;
when 4 =>
exit when I > Data'Last;
State := 5;
C := Unsigned_8 (Data (I));
Into (Pos) := Alphabet (Shift_Right (C and 16#80#, 7) or R);
R := C;
Pos := Pos + 1;
I := I + 1;
when 5 =>
State := 6;
Into (Pos) := Alphabet (Shift_Right (R and 16#7C#, 2));
R := Shift_Left (R, 3) and 16#18#;
Pos := Pos + 1;
when 6 =>
exit when I > Data'Last;
State := 7;
C := Unsigned_8 (Data (I));
Into (Pos) := Alphabet (Shift_Right (C and 16#E0#, 5) or R);
R := C and 16#1F#;
Pos := Pos + 1;
I := I + 1;
when 7 =>
State := 0;
Into (Pos) := Alphabet (R);
Pos := Pos + 1;
end case;
end loop;
E.State := State;
E.Remain := R;
Last := Pos - 1;
Encoded := I - 1;
end Transform;
-- ------------------------------
-- Finish encoding the input array.
-- ------------------------------
overriding
procedure Finish (E : in out Encoder;
Into : in out Ada.Streams.Stream_Element_Array;
Last : in out Ada.Streams.Stream_Element_Offset) is
Pos : Ada.Streams.Stream_Element_Offset := Into'First;
Alphabet : constant Alphabet_Access := E.Alphabet;
R : Unsigned_8 := E.Remain;
begin
-- +---+--------+---+-------+-------+---+------+----+
-- Output: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
-- +---+----+---+---+---+---+---+---+---+---+--+----+
-- Input: | 5 + 3 | 2 + 5 + 1 | 4 + 4 | 1 + 5 + 2 | 3 + 5 |
-- +--------+-----------+-------+-----------+-------+
while E.State /= 0 loop
case E.State is
when 1 =>
E.State := 0;
Into (Pos) := Alphabet (R);
Into (Pos + 1 .. Pos + 7) := (others => Character'Pos ('='));
Pos := Pos + 7;
when 2 =>
E.State := 3;
Into (Pos) := Alphabet (Shift_Right (R and 16#3E#, 1));
R := Shift_Left (R, 4) and 16#10#;
Pos := Pos + 1;
when 3 =>
E.State := 0;
Into (Pos) := Alphabet (R);
Into (Pos + 1 .. Pos + 5) := (others => Character'Pos ('='));
Pos := Pos + 5;
when 4 =>
E.State := 0;
Into (Pos) := Alphabet (R);
Into (Pos + 1 .. Pos + 4) := (others => Character'Pos ('='));
Pos := Pos + 4;
when 5 =>
E.State := 6;
Into (Pos) := Alphabet (Shift_Right (R and 16#7C#, 2));
R := Shift_Left (R, 3) and 16#18#;
Pos := Pos + 1;
when 6 =>
E.State := 0;
Into (Pos) := Alphabet (R);
Into (Pos + 1) := Character'Pos ('=');
Pos := Pos + 2;
when 7 =>
E.State := 0;
Into (Pos) := Alphabet (R);
Pos := Pos + 1;
when others =>
null;
end case;
end loop;
Last := Pos - 1;
end Finish;
-- ------------------------------
-- Set the encoder to use the base64 URL alphabet when <b>Mode</b> is True.
-- The URL alphabet uses the '-' and '_' instead of the '+' and '/' characters.
-- ------------------------------
procedure Set_URL_Mode (E : in out Encoder;
Mode : in Boolean) is
begin
if Mode then
E.Alphabet := BASE32_ALPHABET'Access;
else
E.Alphabet := BASE32_ALPHABET'Access;
end if;
end Set_URL_Mode;
-- ------------------------------
-- Create a base32 encoder using the URL alphabet.
-- ------------------------------
function Create_Encoder return Transformer_Access is
begin
return new Encoder '(Alphabet => BASE32_ALPHABET'Access, others => <>);
end Create_Encoder;
-- ------------------------------
-- Decodes the base32 input stream represented by `Data` into
-- the binary output stream `Into`.
--
-- If the transformer does not have enough room to write the result,
-- it must return in `Encoded` the index of the last encoded
-- position in the `Data` stream.
--
-- The transformer returns in `Last` the last valid position
-- in the output stream `Into`.
--
-- The `Encoding_Error` exception is raised if the input
-- stream cannot be transformed.
-- ------------------------------
overriding
procedure Transform (E : in out Decoder;
Data : in Ada.Streams.Stream_Element_Array;
Into : out Ada.Streams.Stream_Element_Array;
Last : out Ada.Streams.Stream_Element_Offset;
Encoded : out Ada.Streams.Stream_Element_Offset) is
Pos : Ada.Streams.Stream_Element_Offset := Into'First;
I : Ada.Streams.Stream_Element_Offset := Data'First;
C : Ada.Streams.Stream_Element;
Val : Unsigned_8;
Values : constant Alphabet_Values_Access := E.Values;
R : Unsigned_8 := E.Remain;
State : Decode_State_Type := E.State;
-- Get 8 bytes and generate 5 bytes:
-- +---+--------+---+-------+-------+---+------+----+
-- Input: | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 |
-- +---+----+---+---+---+---+---+---+---+---+--+----+
-- Output: | 5 + 3 | 2 + 5 + 1 | 4 + 4 | 1 + 5 + 2 | 3 + 5 |
-- +--------+-----------+-------+-----------+-------+
begin
while Pos <= Into'Last loop
case State is
when 0 =>
exit when I > Data'Last;
State := 1;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
R := Shift_Left (Val, 3);
I := I + 1;
when 1 =>
exit when I > Data'Last;
State := 2;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
Into (Pos) := Stream_Element (R or Shift_Right (Val and 16#1C#, 2));
R := Shift_Left (Val, 6);
Pos := Pos + 1;
I := I + 1;
when 2 =>
exit when I > Data'Last;
State := 3;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
State := Decode_State_Type'Last - 5; -- Expect 5 more '='.
Val := 0;
end if;
R := R or Shift_Left (Val, 1);
I := I + 1;
when 3 =>
exit when I > Data'Last;
State := 4;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
State := Decode_State_Type'Last - 4; -- Expect 4 more '='.
Val := 0;
end if;
Into (Pos) := Stream_Element (R or Shift_Right (Val, 4));
R := Shift_Left (Val, 4);
Pos := Pos + 1;
I := I + 1;
when 4 =>
exit when I > Data'Last;
State := 5;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
State := Decode_State_Type'Last - 3; -- Expect 3 more '='.
else
Into (Pos) := Stream_Element (R or Shift_Right (Val, 1));
R := Shift_Left (Val, 7);
Pos := Pos + 1;
end if;
I := I + 1;
when 5 =>
exit when I > Data'Last;
State := 6;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
State := Decode_State_Type'Last - 2; -- Expect 2 more '='.
else
R := R or Shift_Left (Val, 2);
end if;
I := I + 1;
when 6 =>
exit when I > Data'Last;
State := 7;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
State := Decode_State_Type'Last - 2; -- Expect 2 more '='.
else
Into (Pos) := Stream_Element (R or Shift_Right (Val, 3));
R := Shift_Left (Val, 5);
Pos := Pos + 1;
end if;
I := I + 1;
when 7 =>
exit when I > Data'Last;
State := 0;
C := Data (I);
Val := Values (C);
if (Val and 16#E0#) /= 0 then
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
Val := 0;
State := Decode_State_Type'Last; -- Expect no more '='.
else
Into (Pos) := Stream_Element (R or Val);
Pos := Pos + 1;
end if;
I := I + 1;
when others =>
exit when I > Data'Last;
if State = Decode_State_Type'Last then
raise Encoding_Error with "Garbage after last valid '='";
end if;
C := Data (I);
if C /= Character'Pos ('=') then
raise Encoding_Error with "Invalid character '" & Character'Val (C) & "'";
end if;
State := State + 1;
I := I + 1;
end case;
end loop;
E.State := State;
E.Remain := R;
Last := Pos - 1;
Encoded := I - 1;
end Transform;
-- ------------------------------
-- Finish decoder the input array.
-- ------------------------------
overriding
procedure Finish (E : in out Decoder;
Into : in out Ada.Streams.Stream_Element_Array;
Last : in out Ada.Streams.Stream_Element_Offset) is
begin
-- Reset the state for a next decoding.
E.State := 0;
E.Remain := 0;
Last := Into'First - 1;
end Finish;
-- ------------------------------
-- Set the decoder to use the base64 URL alphabet when <b>Mode</b> is True.
-- The URL alphabet uses the '-' and '_' instead of the '+' and '/' characters.
-- ------------------------------
procedure Set_URL_Mode (E : in out Decoder;
Mode : in Boolean) is
begin
if Mode then
E.Values := BASE32_VALUES'Access;
else
E.Values := BASE32_VALUES'Access;
end if;
end Set_URL_Mode;
-- ------------------------------
-- Create a base64 decoder using the URL alphabet.
-- The URL alphabet uses the '-' and '_' instead of the '+' and '/' characters.
-- ------------------------------
function Create_Decoder return Transformer_Access is
begin
return new Decoder '(Values => BASE32_VALUES'Access, others => <>);
end Create_Decoder;
end Util.Encoders.Base32;
|