Function my_qsort

mysys/mf_qsort.c:97–216

                  const void *cmp_argument)
#else
qsort_t my_qsort(void *base_ptr, size_t count, size_t size, qsort_cmp cmp)
#endif
{
  char *low, *high, *pivot;
  stack_node stack[STACK_SIZE], *stack_ptr;
  my_bool ptr_cmp;
  /* Handle the simple case first */
  /* This will also make the rest of the code simpler */
  if (count <= 1)
    SORT_RETURN;

  low  = (char*) base_ptr;
  high = low+ size * (count - 1);
  stack_ptr = stack + 1;
#ifdef HAVE_purify
  /* The first element in the stack will be accessed for the last POP */
  stack[0].low=stack[0].high=0;
#endif
  pivot = (char *) my_alloca((int) size);
  ptr_cmp= size == sizeof(char*) && !((low - (char*) 0)& (sizeof(char*)-1));

  /* The following loop sorts elements between high and low */
  do
  {
    char *low_ptr, *high_ptr, *mid;

    count=((size_t) (high - low) / size)+1;
    /* If count is small, then an insert sort is faster than qsort */
    if (count < THRESHOLD_FOR_INSERT_SORT)
    {
      for (low_ptr = low + size; low_ptr <= high; low_ptr += size)
      {
	char *ptr;
	for (ptr = low_ptr; ptr > low && CMP(ptr - size, ptr) > 0;
	     ptr -= size)
	  SWAP(ptr, ptr - size, size, ptr_cmp);
      }
      POP(low, high);
      continue;
    }

    /* Try to find a good middle element */
    mid= low + size * (count >> 1);
    if (count > 40)				/* Must be bigger than 24 */
    {
      size_t step = size* (count / 8);
      MEDIAN(low, low + step, low+step*2);
      MEDIAN(mid - step, mid, mid+step);
      MEDIAN(high - 2 * step, high-step, high);
      /* Put best median in 'mid' */
      MEDIAN(low+step, mid, high-step);
      low_ptr  = low;
      high_ptr = high;
    }
    else
    {
      MEDIAN(low, mid, high);
      /* The low and high argument are already in sorted against 'pivot' */