#include <stdio.h>
#include <stdlib.h>

#include <sys/time.h>

#include <libunwind.h>

#define ITERATIONS	10000

#define panic(args...)							  \
	do { fprintf (stderr, args); exit (-1); } while (0)

static int maxlevel = 100;

static inline double
gettime (void)
{
  struct timeval tv;

  gettimeofday(&tv, NULL);
  return tv.tv_sec + 1e-6*tv.tv_usec;
}

static int
measure_unwind (int maxlevel, double *init, double *step)
{
  double stop, mid, start;
  unw_cursor_t cursor;
  unw_context_t uc;
  int ret, level = 0;

  start = gettime ();

  unw_getcontext (&uc);
  if (unw_init_local (&cursor, &uc) < 0)
    panic ("unw_init_local() failed\n");

  mid = gettime ();

  do
    {
      ret = unw_step (&cursor);
      if (ret < 0)
	panic ("unw_step() failed\n");
      ++level;
    }
  while (ret > 0);

  stop = gettime ();

  if (level <= maxlevel)
    panic ("Unwound only %d levels, expected at least %d levels",
	   level, maxlevel);

  *init = mid - start;
  *step = (stop - mid) / (double) level;
  return 0;
}

static int
f1 (int level, int maxlevel, double *init, double *step)
{
  if (level == maxlevel)
    return measure_unwind (maxlevel, init, step);
  else
    /* defeat last-call/sibcall optimization */
    return f1 (level + 1, maxlevel, init, step) + level;
}

static void
doit (const char *label)
{
  double init, step, min_init, first_init, min_step, first_step, sum_init, sum_step;
  int i;

  sum_init = sum_step = first_init = first_step = 0.0;
  min_init = min_step = 1e99;
  for (i = 0; i < ITERATIONS; ++i)
    {
      f1 (0, maxlevel, &init, &step);

      sum_init += init;
      sum_step += step;

      if (init < min_init)
	min_init = init;
      if (step < min_step)
	min_step = step;

      if (i == 0)
	{
	  first_init = init;
	  first_step = step;
	}
    }
  printf ("%s:\n"
	  "  unw_{getcontext+init_local}: first=%9.3f min=%9.3f avg=%9.3f nsec\n"
	  "  unw_step                   : first=%9.3f min=%9.3f avg=%9.3f nsec\n",
	  label,
	  1e9*first_init, 1e9*min_init, 1e9*sum_init/ITERATIONS,
	  1e9*first_step, 1e9*min_step, 1e9*sum_step/ITERATIONS);
}

int
main (int argc, char **argv)
{
  if (argc > 1)
    maxlevel = atol (argv[1]);

  unw_set_caching_policy (unw_local_addr_space, UNW_CACHE_NONE);
  doit ("Caching: none");

  unw_set_caching_policy (unw_local_addr_space, UNW_CACHE_GLOBAL);
  doit ("Caching: global");

  unw_set_caching_policy (unw_local_addr_space, UNW_CACHE_PER_THREAD);
  doit ("Caching: per-thread");

  return 0;
}