[Commit-gnuradio] [gnuradio] 01/09: Add a lookup table to the encoder inner loop for byte mode only (used by the ATSC transmitter).

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trondeau pushed a commit to branch master
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commit 533d392ef938089e24318a771dcf0b7fa5cadbbf
Author: Ron Economos <address@hidden>
Date:   Fri Feb 7 12:58:05 2014 -0800

    Add a lookup table to the encoder inner loop for byte mode only
    (used by the ATSC transmitter).
---
 gr-fec/lib/reed-solomon/char.h      |  1 +
 gr-fec/lib/reed-solomon/encode_rs.c | 12 ++++++++++++
 gr-fec/lib/reed-solomon/init_rs.c   | 23 +++++++++++++++++++++++
 3 files changed, 36 insertions(+)

diff --git a/gr-fec/lib/reed-solomon/char.h b/gr-fec/lib/reed-solomon/char.h
index f76ad95..4d3f22e 100644
--- a/gr-fec/lib/reed-solomon/char.h
+++ b/gr-fec/lib/reed-solomon/char.h
@@ -19,6 +19,7 @@ struct rs {
   unsigned char fcr;        /* First consecutive root, index form */
   unsigned char prim;       /* Primitive element, index form */
   unsigned char iprim;      /* prim-th root of 1, index form */
+  int *modnn_table;         /* modnn lookup table, 512 entries */
 };
 
 static inline unsigned int modnn(struct rs *rs, unsigned int x){
diff --git a/gr-fec/lib/reed-solomon/encode_rs.c 
b/gr-fec/lib/reed-solomon/encode_rs.c
index cd31f32..6a92255 100644
--- a/gr-fec/lib/reed-solomon/encode_rs.c
+++ b/gr-fec/lib/reed-solomon/encode_rs.c
@@ -35,12 +35,24 @@ DTYPE *data, DTYPE *bb){
       feedback = MODNN(NN - GENPOLY[NROOTS] + feedback);
 #endif
       for(j=1;j<NROOTS;j++)
+#ifdef FIXED
+       bb[j] ^= ALPHA_TO[MODNN(feedback + GENPOLY[NROOTS-j])];
+#elif defined(BIGSYM)
        bb[j] ^= ALPHA_TO[MODNN(feedback + GENPOLY[NROOTS-j])];
+#else
+       bb[j] ^= ALPHA_TO[rs->modnn_table[feedback + GENPOLY[NROOTS-j]]];
+#endif
     }
     /* Shift */
     memmove(&bb[0],&bb[1],sizeof(DTYPE)*(NROOTS-1));
     if(feedback != A0)
+#ifdef FIXED
+      bb[NROOTS-1] = ALPHA_TO[MODNN(feedback + GENPOLY[0])];
+#elif defined(BIGSYM)
       bb[NROOTS-1] = ALPHA_TO[MODNN(feedback + GENPOLY[0])];
+#else
+      bb[NROOTS-1] = ALPHA_TO[rs->modnn_table[feedback + GENPOLY[0]]];
+#endif
     else
       bb[NROOTS-1] = 0;
   }
diff --git a/gr-fec/lib/reed-solomon/init_rs.c 
b/gr-fec/lib/reed-solomon/init_rs.c
index f50592b..c3d8921 100644
--- a/gr-fec/lib/reed-solomon/init_rs.c
+++ b/gr-fec/lib/reed-solomon/init_rs.c
@@ -23,6 +23,11 @@ void FREE_RS(void *p){
   free(rs->alpha_to);
   free(rs->index_of);
   free(rs->genpoly);
+#ifdef FIXED
+#elif defined(BIGSYM)
+#else
+  free(rs->modnn_table);
+#endif
   free(rs);
 }
 
@@ -120,6 +125,24 @@ void *INIT_RS(unsigned int symsize,unsigned int 
gfpoly,unsigned fcr,unsigned pri
   for (i = 0; i <= nroots; i++)
     rs->genpoly[i] = rs->index_of[rs->genpoly[i]];
 
+#ifdef FIXED
+#elif defined(BIGSYM)
+#else
+  /* Form modnn lookup table */
+  rs->modnn_table = (int *)malloc(sizeof(int)*(2<<((sizeof(unsigned 
char))*8)));
+  if(rs->modnn_table == NULL){
+    free(rs->genpoly);
+    free(rs->alpha_to);
+    free(rs->index_of);
+    free(rs);
+    return NULL;
+  }
+  for(i = 0; i < (2<<((sizeof(unsigned char))*8)); i++){
+    j = i;
+    rs->modnn_table[i] = modnn(rs,j);
+  }
+#endif
+
 #if 0
   printf ("genpoly:\n");
   for (i = nroots; i >= 0; i--){