init commit

viterbi27_sse.c

@@ -0,0 +1,97 @@
+/* K=7 r=1/2 Viterbi decoder for SSE
+ * Feb 2004, Phil Karn, KA9Q
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <memory.h>
+#include <xmmintrin.h>
+#include "fec.h"
+
+typedef union { unsigned char c[64]; } metric_t;
+typedef union { unsigned long w[2]; unsigned char c[8]; __m64 v[1];} decision_t;
+union branchtab27 { unsigned char c[32]; __m64 v[4];} Branchtab27_sse[2];
+static int Init = 0;
+
+/* State info for instance of Viterbi decoder
+ * Don't change this without also changing references in ssebfly27.s!
+ */
+struct v27 {
+  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_viterbi27_sse(int len){
+  struct v27 *vp;
+  int state;
+
+  if(!Init){
+    /* Initialize branch tables */
+    for(state=0;state < 32;state++){
+      Branchtab27_sse[0].c[state] = parity((2*state) & V27POLYA) ? 255:0;
+      Branchtab27_sse[1].c[state] = parity((2*state) & V27POLYB) ? 255:0;
+    }
+    Init++;
+  }
+  vp = malloc(sizeof(struct v27));
+  vp->decisions = malloc((len+6)*sizeof(decision_t));
+  init_viterbi27(vp,0);
+  return vp;
+}
+
+/* Initialize Viterbi decoder for start of new frame */
+int init_viterbi27_sse(void *p,int starting_state){
+  struct v27 *vp = p;
+  int i;
+
+  for(i=0;i<64;i++)
+    vp->metrics1.c[i] = 63;
+
+  vp->old_metrics = &vp->metrics1;
+  vp->new_metrics = &vp->metrics2;
+  vp->dp = vp->decisions;
+  vp->old_metrics->c[starting_state & 63] = 0; /* Bias known start state */
+  return 0;
+}
+
+/* Viterbi chainback */
+int chainback_viterbi27_sse(
+      void *p,
+      unsigned char *data, /* Decoded output data */
+      unsigned int nbits, /* Number of data bits */
+      unsigned int endstate){ /* Terminal encoder state */
+  struct v27 *vp = p;
+  decision_t *d = vp->decisions;
+
+  /* Make room beyond the end of the encoder register so we can
+   * accumulate a full byte of decoded data
+   */
+  endstate %= 64;
+  endstate <<= 2;
+
+  /* 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 += 6; /* Look past tail */
+  while(nbits-- != 0){
+    int k;
+
+    k = (d[nbits].c[(endstate>>2)/8] >> ((endstate>>2)%8)) & 1;
+    data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
+  }
+  return 0;
+}
+
+/* Delete instance of a Viterbi decoder */
+void delete_viterbi27_sse(void *p){
+  struct v27 *vp = p;
+
+  if(vp != NULL){
+    free(vp->decisions);
+    free(vp);
+  }
+}