Function mergelines

src/sort.c:3397–3428

   are in reverse order.  NLINES must be at least 2.  */

static void
mergelines (struct line *restrict t, size_t nlines,
            struct line const *restrict lo)
{
  size_t nlo = nlines / 2;
  size_t nhi = nlines - nlo;
  struct line *hi = t - nlo;

  while (true)
    if (compare (lo - 1, hi - 1) <= 0)
      {
        *--t = *--lo;
        if (! --nlo)
          {
            /* HI must equal T now, and there is no need to copy from
               HI to T. */
            return;
          }
      }
    else
      {
        *--t = *--hi;
        if (! --nhi)
          {
            do
              *--t = *--lo;
            while (--nlo);

            return;
          }
      }
}

/* Sort the array LINES with NLINES members, using TEMP for temporary space.
   Do this all within one thread.  NLINES must be at least 2.