将uint8_t []转换为IP地址字符串

Question

我目前正在学习C.我的生态系统包括Espressif ESP-32微控制器和Eclipse CDT IDE.

我试图将一个转换uint8_t[]为人类可读的IPv4 address string.到目前为止,我想出了以下代码:

void app_main() {
    uint8_t[] ip = {192, 168, 0, 99};
    dump_ip(ip);
}

void dump_ip(const uint8_t *in) {
    // ip addresses consist of three dots + terminator '\0'
    int size = 4;
    // count amount of chars needed for specific ip address
    for(int i=0; i<4; i++) {
        if(in[i]==0) {
            size ++;
        } else {
            size += ((int)log10(in[i]))+1;
        }
    }
    // allocate memory on heap for an ip address of length 'size'
    char *ip_str = (char*)malloc(size*sizeof(char));
    // copy ip address parts to char array
    int pos = 0;
    for(int i=0; i<4; i++) {
        if(in[i]==0) {
            ip_str[pos] = '0';
            pos++;
        } else {
            char b[4];
            itoa(in[i], b, 10);
            for(int j=0; j<3; j++) {
                if(b[j]!='0') {
                    ip_str[pos] = b[j];
                    pos++;
                }
            }
        }
        // add dot between ip address parts
        if(i<3) {
            ip_str[pos] = '.';
            pos++;
        }
    }
    // add terminator at end of string
    ip_str[pos] = '\0';
    // print to uart interface
    uart_send(ip_str);
    // release allocated heap memory
    free(ip_str);
}

在使用不同的IP阵列进行测试时,我得到以下结果:

uint8_t[] ip = {192, 168, 0, 99};   =>   "192.168.0.99"   => OK
uint8_t[] ip = {192, 168, 1, 99};   =>   "192.168.1"      => FAILED
uint8_t[] ip = {192, 168, 10, 99};  =>   "192.168.1"      => FAILED
uint8_t[] ip = {10, 10, 10, 10};    =>   "1"              => FAILED
// etc. etc. etc. 

我究竟做错了什么？有没有更优雅的方法来实现这一目标？

Answer 1

就是snprintf这样.

void app_main() {
    uint8_t ip[] = {192, 168, 0, 99};
    char buf[3 * 4 + 3 * 1 + 1];
    snprintf(buf, sizeof(buf), "%d.%d.%d.%d", ip[0], ip[1], ip[2], ip[3]);
    uart_send(buf);
}

uint8_t[] ip是无效的C,[]后面是变量名.

1. 的sprintf和snprintf将打印格式的字符串到内存指向的第一个参数.
2. 将snprintf第二个arg作为额外的最大大小参数.
3. 传入变量参数列表时,uint8_t变量会自动转换为int- 因此您可以使用%dprintf修饰符打印它们.
4. 然后你有人类redable,null终止字符串.