import "io"

export { find_free_pages }

let find_free_pages() be
{ let begin = ((! 0x101) >> 11) + 1;
    // begin = first (whole) free page number.
  let end = (! 0x100) >> 11;
    // end = first non-existent page number.
  let num_free = end - begin - 1;
  let pages_needed = (end >> 11) + 1;
    // how many pages needed to store the entire list of free pages
  let free_list = begin << 11;
    // free_list = ptr to list of free pages
  let first_free_page = begin + pages_needed;
  let i, pn, num_entries = pages_needed << 11;
  out("free page list stored at %x to %x\n", free_list, free_list + num_free - 1);
  // next put addresses of free pages in free page list
  i := 0;
  while i < num_free do
  { free_list ! i := (first_free_page + i) << 11;
    i +:= 1 }
  pn := 1;
  while pn < begin do
  { free_list ! i := pn << 11;
    i +:= 1;
    pn +:= 1 }
  while i < num_entries do
  { free_list ! i := 0;
    i +:= 1 }
  resultis free_list }

let start() be
{ let free_page_list = find_free_pages();
  let i = 0;
  out("find_free_pages returned %x\n", free_page_list);
  out("These will be all the free pages: ");
  while free_page_list ! i <> 0 do
  { out(" %d/%x", (free_page_list ! i) >> 11, free_page_list ! i);
    i +:= 1 }
  outch('\n') }