ultracode: Coefficients via fifocache

Author: terryburton

src/ultracode.ps.src

@@ -32,7 +32,7 @@
 % IN THE SOFTWARE.
 
 % --BEGIN ENCODER ultracode--
-% --REQUIRES preamble raiseerror processoptions parseinput setanycolor rendertext renmatrix--
+% --REQUIRES preamble raiseerror processoptions parseinput setanycolor fifocache rendertext renmatrix--
 % --DESC: Ultracode
 % --EXAM: Awesome colours!
 % --EXOP: eclevel=EC2
@@ -44,6 +44,7 @@ true setglobal
 dup /raiseerror dup /uk.co.terryburton.bwipp findresource put
 dup /processoptions dup /uk.co.terryburton.bwipp findresource put
 dup /parseinput dup /uk.co.terryburton.bwipp findresource put
+dup /fifocache dup /uk.co.terryburton.bwipp findresource put
 dup /renmatrix dup /uk.co.terryburton.bwipp findresource put
 begin
 
@@ -152,6 +153,63 @@ begin
     exch get /preload known {//ultracode.latevars /init get exec} if
 } {pop} ifelse
 
+%
+% Function to calculate the product in the field
+%
+/ultracode.rsprod {
+    dup 0 ne { 1 index 0 ne {
+        rslog exch get exch rslog exch get add 282 mod rsalog exch get
+    } { pop pop 0 } ifelse } { pop pop 0 } ifelse
+} bind def
+
+%
+% Generate Reed-Solomon coefficients for a given k
+%
+/ultracode.gencoeffs {
+    /coeffs [ 1 k {0} repeat ] def
+    1 1 k {  % i
+        coeffs 1 index 2 copy 1 sub get put      % coeffs[i] = coeffs[i-1]
+        rsalog 1 index get                       % ai = rsalog[i]
+        exch 1 sub -1 1 {  % j
+            coeffs exch 2 copy get               % ... coeffs j coeffs[j]
+            3 index                              % ... ai
+            //ultracode.rsprod exec              % p = coeffs[j] * ai
+            coeffs 2 index 1 sub get             % ... coeffs[j-1]
+            add 283 mod put                      % coeffs[j] = (p + coeffs[j-1]) mod 283
+        } for
+        coeffs 0 2 copy get                      % coeffs 0 coeffs[0]
+        3 index                                  % ... ai
+        //ultracode.rsprod exec put              % coeffs[0] = coeffs[0] * ai
+        pop  % ai
+    } for
+    /coeffs coeffs 0 coeffs length 1 sub getinterval def
+    coeffs length 1 sub -2 0 { coeffs exch 2 copy get 283 exch sub put } for
+    coeffs
+} bind def
+
+%
+% FIFO cache for ECC polynomials
+%
+% 37 unique keys: qcc=factor*ceil(mcc/25)+5 yields sparse values 3-101
+%
+/ultracode.coeffscachemax 37 def      % Override with global_ctx.ultracode.coeffscachemax
+/ultracode.coeffscachelimit 1311 def  % Override with global_ctx.ultracode.coeffscachelimit
+/uk.co.terryburton.bwipp.global_ctx dup where {
+    exch get
+    dup /ultracode.coeffscachemax 2 copy known {get /ultracode.coeffscachemax exch def} {pop pop} ifelse
+    /ultracode.coeffscachelimit 2 copy known {get /ultracode.coeffscachelimit exch def} {pop pop} ifelse
+} {pop} ifelse
+
+/ultracode.coeffscache ultracode.coeffscachemax ultracode.coeffscachelimit //fifocache exec def
+
+/ultracode.coeffscachefetch {
+    /k exch def
+    k
+    { //ultracode.gencoeffs exec }
+    { length }
+    //ultracode.coeffscache /fetch get exec
+} bind def
+
 /ultracode {
 
     64 dict begin
@@ -290,34 +348,10 @@ begin
     ] def
 
     %
-    % Function to calculate the product in the field
-    %
-    /rsprod {
-        dup 0 ne { 1 index 0 ne {
-            rslog exch get exch rslog exch get add 282 mod rsalog exch get
-        } { pop pop 0 } ifelse } { pop pop 0 } ifelse
-    } def
-
-    %
-    % Generate the coefficients
+    % Fetch the coefficients
     %
     /n mcc def  /k qcc def
-    /coeffs [ 1 k {0} repeat ] def
-    1 1 k {  % i
-        coeffs 1 index 2 copy 1 sub get put      % coeffs[i] = coeffs[i-1]
-        rsalog 1 index get                       % ai = rsalog[i]
-        exch 1 sub -1 1 {  % j
-            coeffs exch 2 copy get               % ... coeffs j coeffs[j]
-            3 index                              % ... ai
-            rsprod                               % p = coeffs[j] * ai
-            coeffs 2 index 1 sub get             % ... coeffs[j-1]
-            add 283 mod put                      % coeffs[j] = (p + coeffs[j-1]) mod 283
-        } for
-        coeffs 0 2 copy get 3 index rsprod put   % coeffs[0] = coeffs[0] * ai
-        pop  % ai
-    } for
-    /coeffs coeffs 0 coeffs length 1 sub getinterval def
-    coeffs length 1 sub -2 0 {coeffs exch 2 copy get 283 exch sub put} for
+    /coeffs k //ultracode.coeffscachefetch exec def
 
     %
     % Derive the error codewords