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with Ada.Text_IO;
-- Nice to have: find optimal code.
separate (Bar_Codes)
package body Encode_Code_128 is
-- See bc_work.xls, sheet: Code_128
subtype Code_Range is Integer range 0 .. 106;
type Sequence is array (Positive range <>) of Code_Range;
function Compose_Code (text : String) return Sequence is
-- Worst case: we switch subcode for each symbol!
max_length : constant Integer := text'Length * 2 + 2;
code : Sequence (1 .. max_length);
code_length : Natural := 0;
--
type Code_128_subcode is (undefined, A, B, C);
subcode : Code_128_subcode := undefined;
checksum : Natural := 0;
--
procedure Add_symbol (symbol : Code_Range) is
begin
checksum := checksum + symbol * Integer'Max (1, code_length);
code_length := code_length + 1;
code (code_length) := symbol;
end Add_symbol;
--
subtype Defined_subcode is Code_128_subcode range A .. C;
--
first_digit : Boolean; -- First digit in a pair of digits for subcode C
--
procedure Switch_to (new_subcode : Defined_subcode) is
begin
if subcode = undefined then
-- Start code A/B/C:
case new_subcode is
when A => Add_symbol (103);
when B => Add_symbol (104);
when C => Add_symbol (105);
end case;
else
case new_subcode is
when A => Add_symbol (101);
when B => Add_symbol (100);
when C => Add_symbol (099);
end case;
end if;
if new_subcode = C then
first_digit := True;
end if;
subcode := new_subcode;
if verbosity_level > 0 then
Ada.Text_IO.Put_Line ("[Code 128] switched to subcode " & subcode'Image);
end if;
end Switch_to;
--
four_digits : Boolean;
digit_buffer, digit : Natural;
begin
for i in text'Range loop
if text (i) > ASCII.DEL then
raise Cannot_Encode with "Message must bit 7-bit ASCII";
end if;
end loop;
for i in text'Range loop
-- Choice of a subcode
case text (i) is
when ASCII.NUL .. ASCII.US =>
if subcode /= A then
Switch_to (A);
end if;
when Character'Val (96) .. ASCII.DEL =>
if subcode /= B then
Switch_to (B);
end if;
when '0' .. '9' =>
if subcode = C then
-- If text (i) is meant to be the first digit of a pair,
-- ensure there is a second digit after.
if first_digit then
if i = text'Last or else text (i + 1) not in '0' .. '9' then
Switch_to (B); -- We need to encode this digit with subcode A or B
end if;
end if;
else
if i + 3 <= text'Last then
four_digits := True;
for j in i + 1 .. i + 3 loop
four_digits := four_digits and text (j) in '0' .. '9';
end loop;
if four_digits then
Switch_to (C);
end if;
end if;
if subcode = undefined then
Switch_to (B);
end if;
end if;
when others =>
-- A or B is good.
if subcode not in A .. B then
Switch_to (B); -- Just an assumption: characters like 'a' .. 'z' more likely.
end if;
end case;
-- Encode text (i)
case subcode is
when undefined => null;
when A =>
if text (i) <= ASCII.US then
Add_symbol (Character'Pos (text (i)) + 64);
else
Add_symbol (Character'Pos (text (i)) - 32);
end if;
when B =>
Add_symbol (Character'Pos (text (i)) - 32);
when C =>
digit := Character'Pos (text (i)) - Character'Pos ('0');
if first_digit then
digit_buffer := digit;
else
Add_symbol (10 * digit_buffer + digit);
end if;
first_digit := not first_digit;
end case;
end loop;
-- Checksum symbol
Add_symbol (checksum mod 103);
-- Stop symbol
Add_symbol (106);
--
return code (1 .. code_length);
end Compose_Code;
-- Here begins the graphics part.
-- Each symbol drawn as a succession of bar, space, bar, space, bar, space.
symbol_width : constant := 11; -- Each symbol has 3 bars and takes 11 "modules" in total.
stop_extra_width : constant := 2; -- Supplemental bar after stop symbol.
procedure Draw (bc : in out Bar_Code; text : String) is
code : constant Sequence := Compose_Code (text);
--
type Width_Sequence is array (1 .. 5) of Positive;
widths : constant array (Code_Range) of Width_Sequence :=
-- These are the widths for: bar, space, bar, space, bar (last space width is implicit).
(
0 => (2, 1, 2, 2, 2),
1 => (2, 2, 2, 1, 2),
2 => (2, 2, 2, 2, 2),
3 => (1, 2, 1, 2, 2),
4 => (1, 2, 1, 3, 2),
5 => (1, 3, 1, 2, 2),
6 => (1, 2, 2, 2, 1),
7 => (1, 2, 2, 3, 1),
8 => (1, 3, 2, 2, 1),
9 => (2, 2, 1, 2, 1),
10 => (2, 2, 1, 3, 1),
11 => (2, 3, 1, 2, 1),
12 => (1, 1, 2, 2, 3),
13 => (1, 2, 2, 1, 3),
14 => (1, 2, 2, 2, 3),
15 => (1, 1, 3, 2, 2),
16 => (1, 2, 3, 1, 2),
17 => (1, 2, 3, 2, 2),
18 => (2, 2, 3, 2, 1),
19 => (2, 2, 1, 1, 3),
20 => (2, 2, 1, 2, 3),
21 => (2, 1, 3, 2, 1),
22 => (2, 2, 3, 1, 1),
23 => (3, 1, 2, 1, 3),
24 => (3, 1, 1, 2, 2),
25 => (3, 2, 1, 1, 2),
26 => (3, 2, 1, 2, 2),
27 => (3, 1, 2, 2, 1),
28 => (3, 2, 2, 1, 1),
29 => (3, 2, 2, 2, 1),
30 => (2, 1, 2, 1, 2),
31 => (2, 1, 2, 3, 2),
32 => (2, 3, 2, 1, 2),
33 => (1, 1, 1, 3, 2),
34 => (1, 3, 1, 1, 2),
35 => (1, 3, 1, 3, 2),
36 => (1, 1, 2, 3, 1),
37 => (1, 3, 2, 1, 1),
38 => (1, 3, 2, 3, 1),
39 => (2, 1, 1, 3, 1),
40 => (2, 3, 1, 1, 1),
41 => (2, 3, 1, 3, 1),
42 => (1, 1, 2, 1, 3),
43 => (1, 1, 2, 3, 3),
44 => (1, 3, 2, 1, 3),
45 => (1, 1, 3, 1, 2),
46 => (1, 1, 3, 3, 2),
47 => (1, 3, 3, 1, 2),
48 => (3, 1, 3, 1, 2),
49 => (2, 1, 1, 3, 3),
50 => (2, 3, 1, 1, 3),
51 => (2, 1, 3, 1, 1),
52 => (2, 1, 3, 3, 1),
53 => (2, 1, 3, 1, 3),
54 => (3, 1, 1, 1, 2),
55 => (3, 1, 1, 3, 2),
56 => (3, 3, 1, 1, 2),
57 => (3, 1, 2, 1, 1),
58 => (3, 1, 2, 3, 1),
59 => (3, 3, 2, 1, 1),
60 => (3, 1, 4, 1, 1),
61 => (2, 2, 1, 4, 1),
62 => (4, 3, 1, 1, 1),
63 => (1, 1, 1, 2, 2),
64 => (1, 1, 1, 4, 2),
65 => (1, 2, 1, 1, 2),
66 => (1, 2, 1, 4, 2),
67 => (1, 4, 1, 1, 2),
68 => (1, 4, 1, 2, 2),
69 => (1, 1, 2, 2, 1),
70 => (1, 1, 2, 4, 1),
71 => (1, 2, 2, 1, 1),
72 => (1, 2, 2, 4, 1),
73 => (1, 4, 2, 1, 1),
74 => (1, 4, 2, 2, 1),
75 => (2, 4, 1, 2, 1),
76 => (2, 2, 1, 1, 1),
77 => (4, 1, 3, 1, 1),
78 => (2, 4, 1, 1, 1),
79 => (1, 3, 4, 1, 1),
80 => (1, 1, 1, 2, 4),
81 => (1, 2, 1, 1, 4),
82 => (1, 2, 1, 2, 4),
83 => (1, 1, 4, 2, 1),
84 => (1, 2, 4, 1, 1),
85 => (1, 2, 4, 2, 1),
86 => (4, 1, 1, 2, 1),
87 => (4, 2, 1, 1, 1),
88 => (4, 2, 1, 2, 1),
89 => (2, 1, 2, 1, 4),
90 => (2, 1, 4, 1, 2),
91 => (4, 1, 2, 1, 2),
92 => (1, 1, 1, 1, 4),
93 => (1, 1, 1, 3, 4),
94 => (1, 3, 1, 1, 4),
95 => (1, 1, 4, 1, 1),
96 => (1, 1, 4, 3, 1),
97 => (4, 1, 1, 1, 1),
98 => (4, 1, 1, 3, 1),
99 => (1, 1, 3, 1, 4),
100 => (1, 1, 4, 1, 3),
101 => (3, 1, 1, 1, 4),
102 => (4, 1, 1, 1, 3),
103 => (2, 1, 1, 4, 1),
104 => (2, 1, 1, 2, 1),
105 => (2, 1, 1, 2, 3),
106 => (2, 3, 3, 1, 1)
);
x : Natural;
--
procedure Bar (offset, width : Natural) is
begin
Filled_Rectangle
(Bar_Code'Class (bc), -- Will use the concrete child method for displaying a rectangle
(left => x + offset,
bottom => 0,
width => width,
height => 1));
end Bar;
begin
-- For vector graphics only: we need to squeeze the full displayed code
-- into the bounding box. A "module" is the thinnest bar.
bc.module_width := bc.bounding.width / Real (code'Length * symbol_width + stop_extra_width);
bc.module_height := bc.bounding.height; -- This is a 1D code: any bar takes the full height
--
for i in code'Range loop
x := (i - 1) * symbol_width;
declare
ws : constant Width_Sequence := widths (code (i));
begin
Bar (0, ws (1));
Bar (ws (1) + ws (2), ws (3));
Bar (ws (1) + ws (2) + ws (3) + ws (4), ws (5));
end;
end loop;
-- Extra bar after the Stop symbol; this gives the Reverse Stop symbol
-- when the bar code is scanned turned 180 degrees.
x := code'Length * symbol_width;
Bar (0, 2);
end Draw;
function Fitting (text : String) return Module_Box is
(0, 0, Compose_Code (text)'Length * symbol_width + stop_extra_width, 1);
end Encode_Code_128;
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