如何在uin8_t类型的结构成员中复制mac-address字符串

Question

使用snprintf函数获得的意外MAC地址值

为什么我会得到“意外的mac-address值。我有很大的字符串（未签名的char数据[DATA_LEN]）要解析并将mac地址复制到结构成员。我得到的字符串完全不同。请对此提供帮助，谢谢” 。

输入数据字符串：

unsigned char data[512] = "its-STRING: 18 22 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 AC 12 00 20 00 00 00 C8 8C DF 9D 57 12 20 00 00 00 29 \n";

程序输出

Parsed Mac from string =  8C DF 9D 57 12 20
copied MacAddress == 32:30:3a:33:38:00

从上述字符串中，我必须提取mac地址“ 8C DF 9D 57 12 20”，然后我必须将此mac地址复制到以下结构中

typedef struct my_stuct_s{
   uint8_t mac_addr[18];
  }my_stuct_t;

下面是我的编码方式。

#define PARSE_OFFSET 89
#define END_OFFESET 19
#define DATA_LEN 512
#define ADDR_LEN 6


typedef struct my_stuct_s{
   uint8_t mac_addr[ADDR_LEN];
   uint8_t item;
}my_stuct_t;


int main()
{
  unsigned char data[DATA_LEN] = "its-STRING: 18 22 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 AC 12 00 20 00 00 00 C8 8C DF 9D 57 12 20 00 00 00 29 \n";
  unsigned char strv6[ADDR_LEN];

  unsigned char *data1 = NULL;

  my_stuct_t shm_memory;

  memset(strv6, 0,sizeof(strv6));
  memset(&shm_memory, 0,sizeof(my_stuct_t));

  if ((strcmp(data, "") ) != 0)
  {
    data1 = &data[0];
    data1 = data1 + PARSE_OFFSET;
    snprintf(strv6, END_OFFESET,"%s\n", data1);

    printf("Parsed Mac from string = %s\n", strv6);
    snprintf((char *)&shm_memory.mac_addr, ADDR_LEN,
            "%02x:%02x:%02x:%02x:%02x:%02x\n",
            strv6[0], strv6[1],
            strv6[2], strv6[3],
            strv6[4], strv6[5]);
 printf("copied MacAddress == %02x:%02x:%02x:%02x:%02x:%02x\n ",
          shm_memory.mac_addr[0],
          shm_memory.mac_addr[1],
          shm_memory.mac_addr[2],
          shm_memory.mac_addr[3],
          shm_memory.mac_addr[4],
          shm_memory.mac_addr[5]);
  }
  else
    printf("\n empty string");


  return 0;
}

Answer 1

1. 您的解析偏移量从89开始，要复制的字符数为18。

   #define PARSE_OFFSET 89
   #define END_OFFESET 19

   应该是
   #define PARSE_OFFSET 90
   #define END_OFFESET 18
   

2. 存储地址的char数组的长度应为19。

   unsigned char strv6[19];

3. 您需要使用sscanf而不是sprintf，如下所示。

   sscanf(strv6, "%02x %02x %02X %02x %02x %02x\n",
     &shm_memory.mac_addr[0],
     &shm_memory.mac_addr[1],
     &shm_memory.mac_addr[2],
     &shm_memory.mac_addr[3],
     &shm_memory.mac_addr[4],
     &shm_memory.mac_addr[5]);