rstplib源码分析---快速生成树之优先级向量

1 源码

   rstplib.1.1.02/vector.c，vector.h

2 功能

   提供生成树优先级向量的基本操作。

3 代码简析

typedef struct bridge_id

{

  unsigned short    prio; //网桥优先级

  unsigned char     addr[6]; //网桥地址

} BRIDGE_ID;

Int STP_VECT_compare_bridge_id (BRIDGE_ID* b1, BRIDGE_ID* b2)

{

  if (b1->prio < b2->prio)

    return -1;

  if (b1->prio > b2->prio)

  return 1;

  return memcmp (b1->addr, b2->addr, 6);

}

typedef unsigned short  PORT_ID;

typedef struct prio_vector_t {

  BRIDGE_ID root_bridge; // 根网桥ID

  unsigned long root_path_cost; // 发送网桥的根路径代价

  BRIDGE_ID design_bridge;// 发送网桥ID(该消息是从哪个网桥发来的)

  PORT_ID   design_port; // 发送端口ID(该消息是从发送网桥的哪个端口发来的)

  PORT_ID   bridge_port; // 接收端口ID(该消息是从本网桥哪个端口接收的)

} PRIO_VECTOR_T;

void STP_VECT_create (OUT PRIO_VECTOR_T* t,

                 IN BRIDGE_ID* root_br,

                 IN unsigned long root_path_cost,

                 IN BRIDGE_ID* design_bridge,

                 IN PORT_ID design_port,

                 IN PORT_ID bridge_port)

{

…

}

Int STP_VECT_compare_vector (PRIO_VECTOR_T* v1, PRIO_VECTOR_T* v2)

{

  int bridcmp;

  bridcmp = STP_VECT_compare_bridge_id (&v1->root_bridge, &v2->root_bridge);

  if (bridcmp < 0) return bridcmp; // bridcmp < 0

  if (! bridcmp) { // bridcmp == 0

    bridcmp = v1->root_path_cost - v2->root_path_cost;

    if (bridcmp < 0) return bridcmp;

      if (! bridcmp) {// bridcmp == 0

      bridcmp = STP_VECT_compare_bridge_id (&v1->design_bridge, &v2->design_bridge);

      if (bridcmp < 0) return bridcmp;

      if (! bridcmp) {// bridcmp == 0

        bridcmp = v1->design_port - v2->design_port;

        if (bridcmp < 0) return bridcmp;

        if (! bridcmp) // bridcmp == 0

          return v1->bridge_port - v2->bridge_port;

      }

    }

  }

  return bridcmp; // bridcmp > 0

}

void STP_VECT_get_vector (IN BPDU_BODY_T* b, OUT PRIO_VECTOR_T* v)

{

  stp_vect_get_bridge_id (b->root_id, &v->root_bridge);

  v->root_path_cost = ntohl (*((long*) b->root_path_cost));

  stp_vect_get_bridge_id (b->bridge_id, &v->design_bridge);

  v->design_port = stp_vect_get_short (b->port_id);

}

void STP_VECT_set_vector (IN PRIO_VECTOR_T* v, OUT BPDU_BODY_T* b)

{

…

}