Get ipv6address prefix content (TO BE FIXED LATER)

void get_ipv6addr_prefix_content(char *ipv6addr,char *prefix)
{
    struct in6_addr ipv6;
    char ipv6_str_r[INET6_ADDRSTRLEN]={0};
    char *p1,*p2;
    int prefix_num;
    char ipaddr_tmp[sizeof(struct in6_addr)];//tmp addr
    int i=0;

    //find '/' and process prefix num
    if(NULL == (p1 = strchr(ipv6addr,'/')))
    {
        printf("IPv6 Address without Prefix!\n");
        exit(1);
    }
    else
    {
        printf("IPv6 Address with Prefix!\n");
        p2 = p1+1;
        prefix_num = atoi(p2);

        char *tmp = ipv6addr;
        static int k = 0;
        while(tmp != p1)
        {
            ipaddr_tmp[k] = *tmp;
            tmp++;
            k++;
        }
        ipaddr_tmp[k-1] = '\0';
    }

    u_int8_t prefix_data[prefix_num/8];

    printf("ipv6address:%s\n", ipv6addr);
    //string to binary
    if (inet_pton(AF_INET6,ipaddr_tmp,&ipv6) <= 0)
    {
        printf("inet_pton failed.");
        exit(1);
    }
    //printf ipv6addr data
    for(;i<16;i++)
    {
        printf("ipv6.s6_addr[%d]:%x\n",i,ipv6.s6_addr[i]);
    }
    printf("=======================================");

    /* process prefix */
    if((prefix_num%2) == 0)//prefix num is even num
    {
        printf("\nThe prefix data\n");

        for(i = 0;i < ((prefix_num)/8);i ++)
        {
            prefix_data[i] = ipv6.s6_addr[i];
            printf("%x\n",prefix_data[i]);
        }

        //tail content set to 0x0
        int j = prefix_num/8;
        while(j<16)
        {
                prefix_data[j] = 0x0;
                j++;
        }
    }
    else //prefix num is odd num
    {
        //to be fixed.
        exit(1);
    }
    printf("=======================================\n");

    //hex to string
    if ( !inet_ntop(AF_INET6, prefix_data,ipv6_str_r,sizeof(ipv6_str_r)) )
    {
        printf("inet_ntop failed.");
        exit(1);
    }
    printf("Get Prefix##_%s\n", ipv6_str_r);

    strcpy(prefix,ipv6_str_r);

}