/* K=7 r=1/2 Viterbi decoder for MMX
 * Copyright Feb 2004, Phil Karn, KA9Q
 */
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <mmintrin.h>
#include "fec.h"

typedef union {
  char c[64];
  __m64 v[8];
} decision_t;
typedef union {
  unsigned char c[64];
  __m64 v[8];
} metric_t;

unsigned char Mettab27_1[256][32] __attribute__((aligned(16)));
unsigned char Mettab27_2[256][32] __attribute__((aligned(16)));
static int Init = 0;

/* State info for instance of Viterbi decoder
 * Don't change this without also changing references in mmxbfly27.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 */
};

/* Initialize Viterbi decoder for start of new frame */
int init_viterbi27_mmx(void *p, int starting_state)
{
  struct v27 *vp = (struct v27 *)p;
  int i;

  if (p == NULL) {
    return -1;
  }
  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;
}

void set_viterbi27_polynomial_mmx(int polys[2])
{
  int state;

  for (state = 0; state < 32; state++) {
    int symbol;
    for (symbol = 0; symbol < 256; symbol++) {
      int sym;

      sym = parity((2 * state) & abs(polys[0])) ^ (polys[0] < 0);
      Mettab27_1[symbol][state] = (sym ? (255 - symbol) : symbol) / 16;

      sym = parity((2 * state) & abs(polys[1])) ^ (polys[1] < 0);
      Mettab27_2[symbol][state] = (sym ? (255 - symbol) : symbol) / 16;
    }
  }
  Init++;
}


/* Create a new instance of a Viterbi decoder */
void *create_viterbi27_mmx(int len)
{
  struct v27 *vp;
  int polys[2] = { V27POLYA, V27POLYB };

  if (Init == 0) {
    set_viterbi27_polynomial_mmx(polys);
  }
  if ((vp = (struct v27 *)malloc(sizeof(struct v27))) == NULL) {
    return NULL;
  }

  if ((vp->decisions = (decision_t *)malloc((len + 6) * sizeof(
                         decision_t))) == NULL) {
    free(vp);
    return NULL;
  }
  init_viterbi27_mmx(vp, 0);
  return vp;
}

/* Viterbi chainback */
int chainback_viterbi27_mmx(
  void *p,
  unsigned char *data, /* Decoded output data */
  unsigned int nbits, /* Number of data bits */
  unsigned int endstate)  /* Terminal encoder state */
{

  struct v27 *vp = (struct v27 *)p;
  decision_t *d;

  if (p == NULL) {
    return -1;
  }
  d = (decision_t *)vp->decisions;
  endstate &= 63;
  d += 6; /* Look past tail */
  while (nbits-- != 0) {
    int k;

    k = d[nbits].c[endstate >> 2] & 1;
    data[nbits >> 3] = endstate = (endstate >> 1) | (k << 7);
  }
  return 0;
}

/* Delete instance of a Viterbi decoder */
void delete_viterbi27_mmx(void *p)
{
  struct v27 *vp = p;

  if (vp != NULL) {
    free(vp->decisions);
    free(vp);
  }
}