ns2中宏定义实现的链表LIST

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ns2中链表的定义在/ns-allinone-2.35/ns2.35/lib/bsd-list.h中。

学习的协议为AOMDV，链表的具体使用在aomdv.h中。

-----------------------------------------------------------链表的定义-----------------------------------------------------------

List的定义：

#define LIST_HEAD(name, type)\struct name {\type *lh_first;/* first element */\}

#define LIST_ENTRY(type)\struct {\type *le_next;/* next element */\type **le_prev;/* address of previous next element */\}

使用结构体定义链表，参数name规定了链表明，type定义了元素的类型。LIST_ENTRY中的成员le_prev，它不是平时双向链表中的前向指针(指向前一个元素)，而是前向前一个元素的le_next成员的指针。le_prev指向的是指针的地址，而不是元素的地址。

aomdv.h中的class AOMDV_Route定义了构造函数：

AOMDV_Route(nsaddr_t nexthop, nsaddr_t lasthop=0) {nh_addr = nexthop;lh_addr = lasthop;  }

之后使用LIST_ENTRY和LIST_HEAD构造了链表元素route_link，链表头为aomdv_routes：

LIST_ENTRY(AOMDV_Route) route_link;LIST_HEAD(aomdv_routes, AOMDV_Route);

---------------------------------------------------------链表的插入/删除----------------------------------------------------------

List Function:

#defineLIST_INIT(head) {\(head)->lh_first = NULL;\}#define LIST_INSERT_AFTER(listelm, elm, field) {\if (((elm)->field.le_next = (listelm)->field.le_next) != NULL)\(listelm)->field.le_next->field.le_prev =\    &(elm)->field.le_next;\(listelm)->field.le_next = (elm);\(elm)->field.le_prev = &(listelm)->field.le_next;\}#define LIST_INSERT_BEFORE(listelm, elm, field) {\(elm)->field.le_prev = (listelm)->field.le_prev;\(elm)->field.le_next = (listelm);\*(listelm)->field.le_prev = (elm);\(listelm)->field.le_prev = &(elm)->field.le_next;\}#define LIST_INSERT_HEAD(head, elm, field) {\if (((elm)->field.le_next = (head)->lh_first) != NULL)\(head)->lh_first->field.le_prev = &(elm)->field.le_next;\(head)->lh_first = (elm);\(elm)->field.le_prev = &(head)->lh_first;\}#define LIST_REMOVE(elm, field) {\if ((elm)->field.le_next != NULL)\(elm)->field.le_next->field.le_prev = \    (elm)->field.le_prev;\*(elm)->field.le_prev = (elm)->field.le_next;\}

aomdv.h中的class AOMDVBroadcastID定义了aomdv_routes类型的后向链表reverse_path_list和前向链表forward_path_list：

aomdv_routes reverse_path_list; // List of reverse paths used for forwarding replies
aomdv_routes forward_path_list; // List of forward paths advertised already

在类AOMDVBroadcastID的构造函数中初始化链表：

        AOMDVBroadcastID(nsaddr_t i, u_int32_t b) { src = i; id = b;  // AOMDV codecount=0;  LIST_INIT(&reverse_path_list);LIST_INIT(&forward_path_list);        }

在类AOMDVBroadcastID的成员函数reverse_path_insert()中将元素插入链表中。（前向链表类似）

        inline AOMDV_Route* reverse_path_insert(nsaddr_t nexthop, nsaddr_t lasthop=0) {  AOMDV_Route* route = new AOMDV_Route(nexthop, lasthop);  assert(route);  LIST_INSERT_HEAD(&reverse_path_list, route, route_link);  return route;        }

链表的遍历：

        inline AOMDV_Route* reverse_path_lookup(nsaddr_t nexthop, nsaddr_t lasthop=0) {  AOMDV_Route *route = reverse_path_list.lh_first;  // Search the list for a match of id  for( ; route; route = route->route_link.le_next) {if ( (route->nh_addr == nexthop) && (route->lh_addr == lasthop) )return route;     }return NULL;}

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