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@lyngklip
lyngklip committed Nov 7, 2024
1 parent a646f76 commit 2497935
Showing 1 changed file with 31 additions and 25 deletions.
56 changes: 31 additions & 25 deletions src/code128.ps.src
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Original file line number Diff line number Diff line change
Expand Up @@ -457,26 +457,33 @@ begin

/max_int 2147483647 def % Make sure state doesn't get picked.

/can_a {c 0 ge {true} {seta c known} ifelse} def % Predicates
/can_b {c 0 ge {true} {setb c known} ifelse} def %
/can_c0 {num_digits 2 ge {true} {setc c known} ifelse} def %
/can_c1 {num_digits 2 ge {true} {setc c known} ifelse} def %
suppressc {/can_c0 {false} def} if % Overruled
suppressc unlatchextbeforec or {/can_c1 {false} def} if % by options
% Predicates for ability to encode:
/can_a {c 0 ge {true} {seta c known} ifelse} def
/can_b {c 0 ge {true} {setb c known} ifelse} def
/can_c0 {num_digits 2 ge {true} {setc c known} ifelse} def
/can_c1 {num_digits 2 ge {true} {setc c known} ifelse} def

% Predicates overruled by options:
suppressc {/can_c0 {false} def} if
suppressc unlatchextbeforec or {/can_c1 {false} def} if

% Output length:
/out_a0 {1 c 0 ge {c 128 ge {1 add} if c 127 and 96 ge {1 add} if} if} def
/out_a1 {1 c 0 ge {c 128 lt {1 add} if c 127 and 96 ge {1 add} if} if} def
/out_b0 {1 c 0 ge {c 128 ge {1 add} if c 127 and 32 lt {1 add} if} if} def
/out_b1 {1 c 0 ge {c 128 lt {1 add} if c 127 and 32 lt {1 add} if} if} def

/map_ab {dup 32 lt {64 add} {32 sub} ifelse} def % Map A and B for the encoding functions below:
/enc_a0 {[c 0 lt {seta c get} {c 128 ge {101} if c 127 and dup 96 ge {98 exch} if map_ab} ifelse]} def % 1 1-3
/enc_a1 {[c 0 lt {seta c get} {c 128 lt {101} if c 127 and dup 96 ge {98 exch} if map_ab} ifelse]} def % 1 1-3
/enc_b0 {[c 0 lt {setb c get} {c 128 ge {100} if c 127 and dup 32 lt {98 exch} if map_ab} ifelse]} def % 1 1-3
/enc_b1 {[c 0 lt {setb c get} {c 128 lt {100} if c 127 and dup 32 lt {98 exch} if map_ab} ifelse]} def % 1 1-3
/enc_c {[c 0 lt {setc c get} {msg n get 48 sub 10 mul msg n 1 add get 48 sub add } ifelse]} def % 1-2 1

/get_best_prior_state { % Unrolled loop helps satisfy the need for speed. Preprocessed input on the stack.
% Encode:
/map_ab {dup 32 lt {64 add} {32 sub} ifelse} def
/enc_a0 {[c 0 lt {seta c get} {c 128 ge {101} if c 127 and dup 96 ge {98 exch} if map_ab} ifelse]} def
/enc_a1 {[c 0 lt {seta c get} {c 128 lt {101} if c 127 and dup 96 ge {98 exch} if map_ab} ifelse]} def
/enc_b0 {[c 0 lt {setb c get} {c 128 ge {100} if c 127 and dup 32 lt {98 exch} if map_ab} ifelse]} def
/enc_b1 {[c 0 lt {setb c get} {c 128 lt {100} if c 127 and dup 32 lt {98 exch} if map_ab} ifelse]} def
/enc_c {[c 0 lt {setc c get} {msg n get 48 sub 10 mul msg n 1 add get 48 sub add } ifelse]} def

% Get best prior state based on a prior row of lengths and a row of latch
% lengths (unrolled and with preprocessed latch lengths on the stack):
/get_best_prior_state {
bln_0 exch get add /len exch def /o exch def
bln_0 exch get add dup len lt {/len exch def /o exch def} {pop pop} ifelse
bln_0 exch get add dup len lt {/len exch def /o exch def} {pop pop} ifelse
Expand All @@ -486,42 +493,41 @@ begin
o
} def

% The Code 128 encoder considers the current row and two rows back (circular buffer size is 4 for convenience):
% The encoder considers the current row and two rows back.
% The circular history buffer size is 4 for convenience.
% The names are short to keep the lines below reasonable:
/bln_0 start_length def /bln_1 start_length def /bln [4 {[0 0 0 0 0 0]} repeat] def % Best Length
/bps_0 start_state def /bps_1 start_state def /bps [4 {[0 0 0 0 0 0]} repeat] def % Best Prior State

% Path for backtracking
% Path for backtracking (could make path a string if it makes a difference):
/path [msg length {[0 0 0 0 0 0]} repeat] def

/make_tables {
/num_digits 0 def
0 1 msg length 1 sub {
/n exch def
/c msg n get def

% Keep a tab on digits:
/num_digits c 48 ge c 58 lt and {num_digits 1 add} {0} ifelse def

% Circular buffer machinery:
% Circular history buffer machinery:
/bln_2 bln_1 def /bln_1 bln_0 def /bln_0 bln n 3 and get def
/bps_2 bps_1 def /bps_1 bps_0 def /bps_0 bps n 3 and get def

% Pick rows for code set c depending on the number of digits encountered:
% Pick history rows for code set c depending on digits:
/bps_c num_digits 2 ge {bps_2} {bps_1} ifelse def
/bln_c num_digits 2 ge {bln_2} {bln_1} ifelse def

% Use the best prior states and the prior best lengths to determine new best lengths. Also, plot the path.
% For example for A and B, pick the best prior state from the previous row, get its length, add latch length and output length.
% Output length for A and B can be 1, 2, or 3 depending on the amount of shifting necessary.
% For C the best prior state may come from the previous row or two rows back depending on input.
% Output length in code set C is always one.
% Use the best prior states and the prior best lengths to determine new best lengths and plot the path:
bln_0 0 can_a {/p bps_1 0 get def path n get 0 p put bln_1 p get latch_length_a0 p get add out_a0 add} {max_int} ifelse put
bln_0 3 can_a {/p bps_1 3 get def path n get 3 p put bln_1 p get latch_length_a1 p get add out_a1 add} {max_int} ifelse put
bln_0 1 can_b {/p bps_1 1 get def path n get 1 p put bln_1 p get latch_length_b0 p get add out_b0 add} {max_int} ifelse put
bln_0 4 can_b {/p bps_1 4 get def path n get 4 p put bln_1 p get latch_length_b1 p get add out_b1 add} {max_int} ifelse put
bln_0 2 can_c0 {/p bps_c 2 get def path n get 2 p put bln_c p get latch_length_c0 p get add 1 add} {max_int} ifelse put
bln_0 5 can_c1 {/p bps_c 5 get def path n get 5 p put bln_c p get latch_length_c1 p get add 1 add} {max_int} ifelse put

% Use the new best lengths to determine new best prior states.
% This is a sort of ping-pong between finding the best length and the best prior states.
% Use the new best lengths to determine new best prior states:
bps_0 0 prioritized_latch_length_a0 aload pop get_best_prior_state put
bps_0 3 prioritized_latch_length_a1 aload pop get_best_prior_state put
bps_0 1 prioritized_latch_length_b0 aload pop get_best_prior_state put
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