Pre-compute numeric runs to avoid O(n^2) complexity

Author: terryburton

src/codablockf.ps.src

@@ -265,27 +265,42 @@ begin
     } if
 
     %
-    % Determine digit runlength and characters from given position
-    %
+    % Pre-compute setC digit runlength from each position; two parity
+    % arrays because FNC1 only counts when s is even. Position after an
+    % FNC4 is its second byte, so numsscr exits there.
+    %
+    /numsAtNEven [ msglen 1 add {0} repeat ] def
+    /numsAtSEven [ msglen 1 add {0} repeat ] def
+    /numsAtNOdd  [ msglen 1 add {0} repeat ] def
+    /numsAtSOdd  [ msglen 1 add {0} repeat ] def
+    msglen 1 sub -1 0 {
+        /i exch def
+        /ch msg i get def
+        i 0 ne { msg i 1 sub get //codablockf.fn4 eq } { false } ifelse {
+            numsAtNEven i 0 put  numsAtSEven i 0 put
+            numsAtNOdd  i 0 put  numsAtSOdd  i 0 put
+        } {
+            setc ch known not {
+                numsAtNEven i 0 put  numsAtSEven i 0 put
+                numsAtNOdd  i 0 put  numsAtSOdd  i 0 put
+            } {
+                ch //codablockf.fn1 eq {
+                    numsAtNEven i 1 numsAtNEven i 1 add get add put
+                    numsAtSEven i 2 numsAtSEven i 1 add get add put
+                    numsAtNOdd  i 0 put
+                    numsAtSOdd  i 0 put
+                } {
+                    numsAtNEven i 1 numsAtNOdd  i 1 add get add put
+                    numsAtSEven i 1 numsAtSOdd  i 1 add get add put
+                    numsAtNOdd  i 1 numsAtNEven i 1 add get add put
+                    numsAtSOdd  i 1 numsAtSEven i 1 add get add put
+                } ifelse
+            } ifelse
+        } ifelse
+    } for
     /numsscr {
-        /n 0 def /s 0 def
-        /p exch def {
-            p msglen ge {exit} if
-            p 0 ne {  % Check not 2nd byte of FNC4
-                msg p 1 sub get //codablockf.fn4 eq {exit} if
-            } if
-            msg p get
-            dup setc exch known not {pop exit} if
-            //codablockf.fn1 eq {
-                % FNC1 in odd position of run like two digits
-                s 2 mod 0 eq {/s s 1 add def} {exit} ifelse
-            } if
-            /n n 1 add def
-            /s s 1 add def
-            /p p 1 add def
-        } loop
-        n s
-    } def
+        dup numsAtNEven exch get exch numsAtSEven exch get
+    } bind def
 
     %
     % Encoding for each alphabet

src/code128.ps.src

@@ -383,25 +383,28 @@ begin
         /msglen msg length def
 
         %
-        % Determine digit runlength from given position
-        %
-        /numsscr {
-            /s 0 def
-            /p exch def {
-                p msglen ge {exit} if
-                msg p get
-                dup setc exch known not {pop exit} if
-                dup -1 le {
-                    % FNC1 in odd position of run like two digits
-                    //code128.fn1 eq s 2 mod 0 eq and {/s s 1 add def} {exit} ifelse
+        % Pre-compute setC digit runlength from each position; two parity
+        % arrays because FNC1 only counts when s is even.
+        %
+        /numsAtEven [ msglen 1 add {0} repeat ] def
+        /numsAtOdd  [ msglen 1 add {0} repeat ] def
+        msglen 1 sub -1 0 {
+            /i exch def
+            /c msg i get def
+            c //code128.fn1 eq {
+                numsAtEven i 2 numsAtEven i 1 add get add put
+                numsAtOdd  i 0 put
+            } {
+                c 48 ge c 57 le and {
+                    numsAtEven i 1 numsAtOdd  i 1 add get add put
+                    numsAtOdd  i 1 numsAtEven i 1 add get add put
                 } {
-                    pop
+                    numsAtEven i 0 put
+                    numsAtOdd  i 0 put
                 } ifelse
-                /s s 1 add def
-                /p p 1 add def
-            } loop
-            s
-        } def
+            } ifelse
+        } for
+        /numsscr { numsAtEven exch get } bind def
 
         %
         % Encoding for each alphabet

src/code16k.ps.src

@@ -357,24 +357,36 @@ begin
         /msglen msg length def
 
         %
-        % Determine digit runlength and characters from given position
+        % Pre-compute setC digit runlength from each position; two parity
+        % arrays because FNC1 only counts when s is even.
         %
+        /numsAtNEven [ msglen 1 add {0} repeat ] def
+        /numsAtSEven [ msglen 1 add {0} repeat ] def
+        /numsAtNOdd  [ msglen 1 add {0} repeat ] def
+        /numsAtSOdd  [ msglen 1 add {0} repeat ] def
+        msglen 1 sub -1 0 {
+            /i exch def
+            /ch msg i get def
+            setc ch known not {
+                numsAtNEven i 0 put  numsAtSEven i 0 put
+                numsAtNOdd  i 0 put  numsAtSOdd  i 0 put
+            } {
+                ch //code16k.fn1 eq {
+                    numsAtNEven i 1 numsAtNEven i 1 add get add put
+                    numsAtSEven i 2 numsAtSEven i 1 add get add put
+                    numsAtNOdd  i 0 put
+                    numsAtSOdd  i 0 put
+                } {
+                    numsAtNEven i 1 numsAtNOdd  i 1 add get add put
+                    numsAtSEven i 1 numsAtSOdd  i 1 add get add put
+                    numsAtNOdd  i 1 numsAtNEven i 1 add get add put
+                    numsAtSOdd  i 1 numsAtSEven i 1 add get add put
+                } ifelse
+            } ifelse
+        } for
         /numsscr {
-            /n 0 def /s 0 def
-            /p exch def {
-                p msglen ge {exit} if
-                msg p get
-                dup setc exch known not {pop exit} if
-                //code16k.fn1 eq {
-                    % FNC1 in odd position of run like two digits
-                    s 2 mod 0 eq {/s s 1 add def} {exit} ifelse
-                } if
-                /n n 1 add def
-                /s s 1 add def
-                /p p 1 add def
-            } loop
-            n s
-        } def
+            dup numsAtNEven exch get exch numsAtSEven exch get
+        } bind def
 
         %
         % Encoding for each alphabet