Extract fec-3.0.1

1 files changed, 190 insertions, 0 deletions

diff --git a/viterbi29_av.c b/viterbi29_av.c
new file mode 100644
index 0000000..31c8d27
--- /dev/null
+++ b/viterbi29_av.c
@@ -0,0 +1,190 @@
+/* K=9 r=1/2 Viterbi decoder for PowerPC G4/G5 Altivec
+ * Copyright Feb 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 <sys/sysctl.h>
+#include "fec.h"
+
+typedef union { unsigned char c[256]; vector bool char v[16]; } decision_t;
+typedef union { unsigned char c[256]; vector unsigned char v[16]; } metric_t;
+
+static union branchtab29 { unsigned char c[128]; vector unsigned char v[8]; } Branchtab29[2];
+static int Init = 0;
+
+/* State info for instance of Viterbi decoder */
+struct v29 {
+  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 */
+};
+
+/* Initialize Viterbi decoder for start of new frame */
+int init_viterbi29_av(void *p,int starting_state){
+  struct v29 *vp = p;
+  int i;
+
+  if(p == NULL)
+    return -1;
+  for(i=0;i<16;i++)
+    vp->metrics1.v[i] = (vector unsigned char)(63);
+
+  vp->old_metrics = &vp->metrics1;
+  vp->new_metrics = &vp->metrics2;
+  vp->dp = vp->decisions;
+  vp->old_metrics->c[starting_state & 255] = 0; /* Bias known start state */
+  return 0;
+}
+
+void set_viterbi29_polynomial_av(int polys[2]){
+  int state;
+
+  for(state=0;state < 128;state++){
+    Branchtab29[0].c[state] = (polys[0] < 0) ^ parity((2*state) & abs(polys[0])) ? 255 : 0;
+    Branchtab29[1].c[state] = (polys[1] < 0) ^ parity((2*state) & abs(polys[1])) ? 255 : 0;
+  }
+  Init++;
+}
+
+/* Create a new instance of a Viterbi decoder */
+void *create_viterbi29_av(int len){
+  struct v29 *vp;
+
+  if(!Init){
+    int polys[2] = { V29POLYA,V29POLYB };
+    set_viterbi29_polynomial_av(polys);
+  }
+  if((vp = (struct v29 *)malloc(sizeof(struct v29))) == NULL)
+    return NULL;
+  if((vp->decisions = (decision_t *)malloc((len+8)*sizeof(decision_t))) == NULL){
+    free(vp);
+    return NULL;
+  }
+  init_viterbi29_av(vp,0);
+  return vp;
+}
+
+/* Viterbi chainback */
+int chainback_viterbi29_av(
+      void *p,
+      unsigned char *data, /* Decoded output data */
+      unsigned int nbits, /* Number of data bits */
+      unsigned int endstate){ /* Terminal encoder state */
+  struct v29 *vp = p;
+  decision_t *d;
+
+  if(p == NULL)
+    return -1;
+  d = (decision_t *)vp->decisions;  
+  /* Make room beyond the end of the encoder register so we can
+   * accumulate a full byte of decoded data
+   */
+  endstate %= 256;
+
+  /* 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 += 8; /* Look past tail */
+  while(nbits-- != 0){
+    int k;
+    
+    k = d[nbits].c[endstate] & 1;
+    data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
+  }
+  return 0;
+}
+
+
+/* Delete instance of a Viterbi decoder */
+void delete_viterbi29_av(void *p){
+  struct v29 *vp = p;
+
+  if(vp != NULL){
+    free(vp->decisions);
+    free(vp);
+  }
+}
+
+
+int update_viterbi29_blk_av(void *p,unsigned char *syms,int nbits){
+  struct v29 *vp = p;
+  decision_t *d;
+  int i;
+
+  if(p == NULL)
+    return -1;
+  d = (decision_t *)vp->dp;
+
+  while(nbits--){
+    vector unsigned char sym1v,sym2v;
+    void *tmp;
+    
+    /* All this seems necessary just to load a byte into all elements of a vector! */
+    sym1v = vec_perm(vec_ld(0,syms),vec_ld(1,syms),vec_lvsl(0,syms)); /* sym1v.0 = syms[0]; sym1v.1 = syms[1] */
+    sym2v = vec_splat(sym1v,1); /* Splat syms[1] across sym2v */
+    sym1v = vec_splat(sym1v,0); /* Splat syms[0] across sym1v */
+    syms += 2;
+    
+    for(i=0;i<8;i++){
+      vector bool char decision0,decision1;
+      vector unsigned char metric,m_metric,m0,m1,m2,m3,survivor0,survivor1;
+
+      /* Form branch metrics */
+      metric = vec_avg(vec_xor(Branchtab29[0].v[i],sym1v),vec_xor(Branchtab29[1].v[i],sym2v));
+      metric = vec_sr(metric,(vector unsigned char)(3));
+      m_metric = (vector unsigned char)(31) - metric;
+    
+      /* Add branch metrics to path metrics */
+      m0 = vec_adds(vp->old_metrics->v[i],metric);
+      m3 = vec_adds(vp->old_metrics->v[8+i],metric);
+      m1 = vec_adds(vp->old_metrics->v[8+i],m_metric);
+      m2 = vec_adds(vp->old_metrics->v[i],m_metric);
+    
+      /* Compare and select first set */
+      decision0 = vec_cmpgt(m0,m1);
+      decision1 = vec_cmpgt(m2,m3);
+      survivor0 = vec_min(m0,m1);
+      survivor1 = vec_min(m2,m3);
+
+      /* Interleave and store decisions and survivors */
+      d->v[2*i] = vec_mergeh(decision0,decision1);
+      d->v[2*i+1] = vec_mergel(decision0,decision1);
+      vp->new_metrics->v[2*i] = vec_mergeh(survivor0,survivor1);
+      vp->new_metrics->v[2*i+1] = vec_mergel(survivor0,survivor1);
+    }
+    d++;
+    /* renormalize if necessary */
+    if(vp->new_metrics->c[0] >= 50){
+      int i;
+      vector unsigned char scale0,scale1;
+
+      /* Find smallest metric and splat */
+      scale0 = vp->new_metrics->v[0];
+      scale1 = vp->new_metrics->v[1];
+      for(i=2;i<16;i+=2){
+	scale0 = vec_min(scale0,vp->new_metrics->v[i]);
+	scale1 = vec_min(scale1,vp->new_metrics->v[i+1]);
+      }
+      scale0 = vec_min(scale0,scale1);
+      scale0 = vec_min(scale0,vec_sld(scale0,scale0,8));
+      scale0 = vec_min(scale0,vec_sld(scale0,scale0,4));
+      scale0 = vec_min(scale0,vec_sld(scale0,scale0,2));
+      scale0 = vec_min(scale0,vec_sld(scale0,scale0,1));
+
+      /* Now subtract from all metrics */
+      for(i=0;i<16;i++)
+	vp->new_metrics->v[i] = vec_subs(vp->new_metrics->v[i],scale0);
+    }
+    /* 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;
+}