/*
 * vim:tw=76:ts=2:sw=2:cindent:expandtab
 */

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <unistd.h>
#include <stdint.h>
#include <inttypes.h>

#include "reciprocal_div64.h"
#include "intrange.h"
#include "salsarnd.h"

int main(int argc, char *argv[])
{
  int64_t i;
  uint64_t *shuf;
  uint64_t tmp;
  uint64_t rnd = 0;
  uint64_t lo, hi;
  uint64_t nr;
  uint64_t flagmask;
  struct reciprocal_value64 recip;
  char *p;
  int flagknuth;

  if (argc != 4) _exit(1);
  flagknuth = *argv[3] - '0';
  errno = 0;
  lo = strtoull(argv[1], &p, 10);
  if ((errno != 0) || (argv[1] == p)) _exit(2);
  hi = strtoull(argv[2], &p, 10);
  if ((errno != 0) || (argv[2] == p)) _exit(2);
  if (lo == hi) {
    printf("%" PRIu64 "\n", lo);
    fflush(stdout);
    return 0;
  }
  if (lo > hi) {
    _exit(2);
  }
  nr = hi - lo + 1;
  if (nr > (SIZE_MAX / sizeof(uint64_t))) _exit(3);
  shuf = malloc(nr * sizeof(uint64_t));
  if (!shuf) _exit(4);
  for (i = 0; lo <= hi; i++, lo++) {
    shuf[i] = lo;
  }

  if (flagknuth) {
    i = nr;
    while (i > 1) {
      rnd = randrange_u64(i, randrange_val64(i));
      i--;
      tmp = shuf[rnd];
      shuf[rnd] = shuf[i];
      shuf[i] = tmp;
    }
  } else if ((nr & (nr-1)) == 0) {
    flagmask = nr-1;
    for (i = nr - 1; i >= 0; i--) {
      rnd = get_random64() & flagmask;
      tmp = shuf[i];
      shuf[i] = shuf[rnd];
      shuf[rnd] = tmp;
    }
  } else {
    recip = reciprocal_value64(nr);
    for (i = nr - 1; i >= 0; i--) {
      rnd = reciprocal_remainder64(get_random64(), nr, recip);
      tmp = shuf[i];
      shuf[i] = shuf[rnd];
      shuf[rnd] = tmp;
    }
  }

  for (i = 0; i < nr; i++) printf("%" PRIu64 "\n", shuf[i]);

  fflush(stdout);
  return 0;
}