Returning an array from function

I am writing a function which takes in the integer value and the pointer to a character. the function converts the integer value into binary and stores it in the char pointer. the char pointer is 16 bytes long.

Snippet of code:

void int2bin(u_int16_t addr_IP, char *Binary)
{
    int count;
    printf("IP1add = %d \n", Binary);
    for (count = 0; count < 16; count++) {
        if(addr_IP>0)
            *(Binary + 15-count) = addr_IP & 开发者_运维知识库0x1 ? '1':'0';
        else
            *(Binary + 15-count) = '0';

          addr_IP>>=1;
    }   
}

int main(int argc, char *argv[])
{
    u_int16_t senderIP_16[], u_int16_t receiverIP_16[];
    char  sender_IP_hi[16], sender_IP_low[16];
    int2bin(senderIP_16[0], &sender_IP_hi);
    int2bin(senderIP_16[1], &sender_IP_low);
}

In the first call to the function, it returns correct values. But in the second pass, the value of first pass is appended to the second pass, i.e length of sender_IP_low becomes 32.

How can I resolve this?

Thanks

---

It looks like you're printing sender_IP_low as a string, and since it is not null-terminated, the print routine continues to print the adjacent buffer, sender_IP_hi. And you're probably just lucky that the print routine finds a zero and stops before a segmentation fault.

One quick fix is:

void int2bin(u_int16_t addr_IP, char *Binary) {
    ...

    Binary[16] = 0; // terminate the string before returning
}

...

char  sender_IP_hi[17], sender_IP_low[17]; // +1 for null terminator

Although, there are a few other things that could be fixed in your implementation, I just wanted to focus on an answer to your original question.

---

If you are printing the arrays with printf():

void int2bin(u_int16_t addr_IP, char *Binary)
{
    int count;
    printf("IP1add = %d \n", Binary);
    for (count = 0; count < 16; count++) {
        if(addr_IP>0)
            *(Binary + 15-count) = addr_IP & 0x1 ? '1':'0';
        else
            *(Binary + 15-count) = '0';

          addr_IP>>=1;
    }   
    // Put the NULL char in the last position
    Binary[16] = '\0';
}

int main(int argc, char *argv[])
{
    u_int16_t senderIP_16[], u_int16_t receiverIP_16[];
    // One more char for storing the terminator character
    char  sender_IP_hi[17], sender_IP_low[17];
    int2bin(senderIP_16[0], &sender_IP_hi);
    int2bin(senderIP_16[1], &sender_IP_low);
}