在contiki中使用rime时如何管理指针？ [英] How do I manage pointers when using rime in contiki?

问题描述

在我的场景中我有2个节点：发送者和接收者。



节点1向接收者发送数据包，请求是一些指向某些字符串的char指针数组：

Hi, In my scenario I have 2 node: sender and receiver.

node 1 sends packets to receiver and request is an array of char pointers to some strings:

packetbuf_copyfrom(request[i], strlen(request[i]));

在接收器中我想将收到的数据包添加到列表中：



但是当我想打印收到的数据包列表时，它只打印最后一个数据包收到，即。所有列表元素都指向最后一个字符串。



如何管理指针来解决这个问题？



我尝试过：

And in receiver I want to add received packets to a list :

but when I want to print the list of received packets it prints only the last packet received, ie. all of list elements points to the last string.

How do I manage pointers to solve this issue?

What I have tried:

#include "contiki.h"

#include "dev/leds.h"

#include <stdio.h>
#define MAX_RECORD 20
struct record{
	struct record *next;
	char* message;

};
MEMB(record_memb, struct record,MAX_RECORD);
LIST(record_list);
/*---------------------------------------------------------------------------*/
PROCESS(example_unicast_process, "Example unicast");
AUTOSTART_PROCESSES(&example_unicast_process);
/*---------------------------------------------------------------------------*/
static void
recv_uc(struct unicast_conn *c, const linkaddr_t *from)
{
  printf("unicast message received from %d.%d : %s\n",
	 from->u8[0], from->u8[1],(char *)packetbuf_dataptr());
char* temp = (char *)packetbuf_dataptr();
struct record *n; 

n = memb_alloc(&record_memb);
 
n-> message = temp; 

list_add(record_list,n);
for(n = list_head(record_list); n != NULL; n = n->next) {

  printf(" = %s \n", n->message);
}//end for
  

}
static const struct unicast_callbacks unicast_callbacks = {recv_uc};
static struct unicast_conn uc;
/*---------------------------------------------------------------------------*/
PROCESS_THREAD(example_unicast_process, ev, data)
{
  PROCESS_EXITHANDLER(unicast_close(&uc);)
    
  PROCESS_BEGIN();

  unicast_open(&uc, 146, &unicast_callbacks);
  static int i = 1;
  while(1) {
    static struct etimer et;
    linkaddr_t addr;
    
    etimer_set(&et, CLOCK_SECOND);
    
    PROCESS_WAIT_EVENT_UNTIL(etimer_expired(&et));
 char * arr= "hello";
if(i == 2 ){
    i = 1; packetbuf_copyfrom("hello", 5);
} else {  packetbuf_copyfrom("good bye baby", 14); i = 2; }
 
    addr.u8[0] = 1;
    addr.u8[1] = 0;
    if(!linkaddr_cmp(&addr, &linkaddr_node_addr)) {
      unicast_send(&uc, &addr);
    }

  }

  PROCESS_END();
}
/*------------

推荐答案

引用：

但是当我想要打印收到的数据包列表，它只打印最后收到的数据包，即。所有列表元素都指向最后一个字符串。

but when I want to print the list of received packets it prints only the last packet received, ie. all of list elements points to the last string.

这是因为记录结构的消息成员是一个 char * 指针，对于所有添加的项目，它被设置为 packetbuf_dataptr（）。此数据包缓冲区当然包含最后收到的消息。



您必须为字符串分配内存并复制它们：

That is because the message member of your record structure is a char* pointer which is set to packetbuf_dataptr() for all added items. This packet buffer contains off course always the last received message.

You have to allocate memory for the strings and copy them:

n = memb_alloc(&record_memb);
n->message = malloc(1 + strlen(temp));
strcpy(n->message, temp);
list_add(record_list,n);

请注意，从列表中删除项目时以及删除列表本身之前，您已删除已分配的内存。

Note that you have delete the allocated memory when removing items from the list and before deleting the list itself.

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