/* K=9 r=1/2 Viterbi decoder for SSE2
 * 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 <emmintrin.h>
#include "fec.h"

typedef union {
  unsigned char c[256];
  __m128i v[16];
} metric_t;
typedef union {
  unsigned long w[8];
  unsigned char c[32];
} decision_t;

union branchtab29 {
  unsigned char c[128];
} Branchtab29_sse2[2];
static int Init = 0;

/* State info for instance of Viterbi decoder
 * Don't change this without also changing references in sse2bfly29.s!
 */
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_sse2(void *p, int starting_state)
{
  struct v29 *vp = p;
  int i;

  for (i = 0; i < 256; 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 & 255] = 0; /* Bias known start state */
  return 0;
}

void set_viterbi29_polynomial_sse2(int polys[2])
{
  int state;

  for (state = 0; state < 128; state++) {
    Branchtab29_sse2[0].c[state] = (polys[0] < 0) ^ parity((2 * state) & abs(
                                     polys[0])) ? 255 : 0;
    Branchtab29_sse2[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_sse2(int len)
{
  void *p;
  struct v29 *vp;

  if (!Init) {
    int polys[2] = {V29POLYA, V29POLYB};

    set_viterbi29_polynomial(polys);
  }
  /* Ordinary malloc() only returns 8-byte alignment, we need 16 */
  if (posix_memalign(&p, sizeof(__m128i), sizeof(struct v29))) {
    return NULL;
  }
  vp = (struct v29 *)p;
  if ((p = malloc((len + 8) * sizeof(decision_t))) == NULL) {
    free(vp);
    return NULL;
  }
  vp->decisions = (decision_t *)p;
  init_viterbi29_sse2(vp, 0);
  return vp;
}


/* Viterbi chainback */
int chainback_viterbi29_sse2(
  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 = 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 / 8] >> (endstate % 8)) & 1;
    data[nbits >> 3] = endstate = (endstate >> 1) | (k << 7);
  }
  return 0;
}


/* Delete instance of a Viterbi decoder */
void delete_viterbi29_sse2(void *p)
{
  struct v29 *vp = p;

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