dl_sorted_insert

#define DL_SORTED_INSERT(head,add,cmp)                       \
  do {                                                       \
    LDECLTYPE(head) _pos;                                    \
    _pos = (head);                                           \
    DL_FIND_POS(_pos,add,cmp);                               \
    DL_INSERT(head,_pos,add);                                \
  } while (0)

#define DL_INSERT(head,pos,add)                              \
  DL_INSERT2(head, pos,add,prev,next)                        \

#define DL_INSERT2(head,pos,add,prev,next)                   \
  do {                                                       \
    if ((pos) == NULL) {                                     \
      DL_PREPEND(head,add);                                  \
    } else {                                                 \
      DL_INSERT_AFTER(pos,add);                              \
      if ((add)->next == NULL) {                             \
        (head)->prev = (add);                                \
      }                                                      \
    }                                                        \
  } while (0)

#define DL_INSERT_AFTER(prior,add)                           \
  DL_INSERT_AFTER2(prior,add,prev,next)                      \

#define DL_INSERT_AFTER2(prior,add,prev,next)                \
  do {                                                       \
    (add)->next = (prior)->next;                             \
    (prior)->next = (add);                                   \
    (add)->prev = (prior);                                   \
    if ((add)->next) {                                       \
      (add)->next->prev = (add);                             \
    }                                                        \
  } while (0)

#define DL_FIND_POS(head,node,cmp)                           \
  DL_FIND_POS2(head,node,cmp,prev,next)                      \

#define DL_FIND_POS2(head,node,cmp,prev,next)                \
  do {                                                       \
    if (cmp((head), (node)) > 0) {                           \
      (head) = NULL;                                         \
    } else {                                                 \
      for (; (head)->next != NULL; head = (head)->next ) {   \
        if (cmp((head)->next, (node)) > 0) {                 \
          break;                                             \
        }                                                    \
      }                                                      \
    }                                                        \
  } while (0)