1 files changed, 156 insertions, 0 deletions
diff --git a/viterbi615_port.c b/viterbi615_port.c
new file mode 100644
index 0000000..89bdd80
--- /dev/null
+++ b/viterbi615_port.c
@@ -0,0 +1,156 @@
+/* K=15 r=1/6 Viterbi decoder in portable C
+ * Copyright Mar 2004, Phil Karn, KA9Q
+ * May be used under the terms of the GNU Lesser General Public License (LGPL)
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <memory.h>
+#include <limits.h>
+#include "fec.h"
+
+typedef union { unsigned long w[512]; unsigned char c[2048];} decision_t;
+typedef union { unsigned long w[16384]; } metric_t;
+
+static union branchtab615 { unsigned long w[8192]; } Branchtab615[6] __attribute__ ((aligned(16)));
+static int Init = 0;
+
+/* State info for instance of Viterbi decoder */
+struct v615 {
+  metric_t metrics1; /* path metric buffer 1 */
+  metric_t metrics2; /* path metric buffer 2 */
+  decision_t *dp;          /* Pointer to current decision */
+  metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */
+  decision_t *decisions;   /* Beginning of decisions for block */
+};
+
+/* Create a new instance of a Viterbi decoder */
+void *create_viterbi615_port(int len){
+  struct v615 *vp;
+
+  if(!Init){
+    int polys[6] = { V615POLYA,V615POLYB,V615POLYC,V615POLYD,V615POLYE,V615POLYF };
+    set_viterbi615_polynomial_port(polys);
+  }
+  if((vp = (struct v615 *)malloc(sizeof(struct v615))) == NULL)
+    return NULL;
+  if((vp->decisions = malloc((len+14)*sizeof(decision_t))) == NULL){
+    free(vp);
+    return NULL;
+  }
+  init_viterbi615(vp,0);
+  return vp;
+}
+
+void set_viterbi615_polynomial_port(int polys[6]){
+  int state;
+  int i;
+
+  for(state=0;state < 8192;state++){
+    for(i=0;i<6;i++)
+      Branchtab615[i].w[state] = (polys[i] < 0) ^ parity((2*state) & abs(polys[i])) ? 255 : 0;
+  }
+  Init++;
+}
+
+/* Initialize Viterbi decoder for start of new frame */
+int init_viterbi615_port(void *p,int starting_state){
+  struct v615 *vp = p;
+  int i;
+
+  if(p == NULL)
+    return -1;
+  for(i=0;i<16384;i++)
+    vp->metrics1.w[i] = 1000;
+
+  vp->old_metrics = &vp->metrics1;
+  vp->new_metrics = &vp->metrics2;
+  vp->dp = vp->decisions;
+  vp->old_metrics->w[starting_state & 16383] = 0; /* Bias known start state */
+  return 0;
+}
+
+/* Viterbi chainback */
+int chainback_viterbi615_port(
+      void *p,
+      unsigned char *data, /* Decoded output data */
+      unsigned int nbits, /* Number of data bits */
+      unsigned int endstate){ /* Terminal encoder state */
+  struct v615 *vp = p;
+  decision_t *d;
+
+  if(p == NULL)
+    return -1;
+  d = (decision_t *)vp->decisions;  
+  endstate %= 16384;
+
+  /* The store into data[] only needs to be done every 8 bits.
+   * But this avoids a conditional branch, and the writes will
+   * combine in the cache anyway
+   */
+  d += 14; /* Look past tail */
+  while(nbits-- != 0){
+    int k;
+
+    k = (d[nbits].c[endstate/8] >> (endstate%8)) & 1;
+    endstate = (k << 13) | (endstate >> 1);
+    data[nbits>>3] = endstate >> 6;
+  }
+  return 0;
+}
+
+/* Delete instance of a Viterbi decoder */
+void delete_viterbi615_port(void *p){
+  struct v615 *vp = p;
+
+  if(vp != NULL){
+    free(vp->decisions);
+    free(vp);
+  }
+}
+
+/* C-language butterfly */
+#define BFLY(i) {\
+unsigned long metric,m0,m1,m2,m3,decision0,decision1;\
+    metric = ((Branchtab615[0].w[i] ^ syms[0]) + (Branchtab615[1].w[i] ^ syms[1])\
+	      +(Branchtab615[2].w[i] ^ syms[2]) + (Branchtab615[3].w[i] ^ syms[3])\
+	      +(Branchtab615[4].w[i] ^ syms[4]) + (Branchtab615[5].w[i] ^ syms[5]));\
+    m0 = vp->old_metrics->w[i] + metric;\
+    m1 = vp->old_metrics->w[i+8192] + (1530 - metric);\
+    m2 = vp->old_metrics->w[i] + (1530-metric);\
+    m3 = vp->old_metrics->w[i+8192] + metric;\
+    decision0 = (signed long)(m0-m1) >= 0;\
+    decision1 = (signed long)(m2-m3) >= 0;\
+    vp->new_metrics->w[2*i] = decision0 ? m1 : m0;\
+    vp->new_metrics->w[2*i+1] = decision1 ? m3 : m2;\
+    d->c[i/4] |= ((decision0|(decision1<<1)) << ((2*i)&7));\
+}
+/* Update decoder with a block of demodulated symbols
+ * Note that nbits is the number of decoded data bits, not the number
+ * of symbols!
+ */
+
+int update_viterbi615_blk_port(void *p,unsigned char *syms,int nbits){
+  struct v615 *vp = p;
+  void *tmp;
+  decision_t *d;
+  int i;
+
+  if(p == NULL)
+    return -1;
+  d = (decision_t *)vp->dp;
+  while(nbits--){
+    memset(d,0,sizeof(decision_t));
+    for(i=0;i<8192;i++)
+      BFLY(i);
+
+    syms += 6;
+    d++;
+    /* Swap pointers to old and new metrics */
+    tmp = vp->old_metrics;
+    vp->old_metrics = vp->new_metrics;
+    vp->new_metrics = tmp;
+  }    
+  vp->dp = d;
+  return 0;
+}
+