Question

I have to copy data into sets of 16 bytes. How do i do it with an easy way?
I’ve come up with the below algorithm but how do i know if the null terminator has been added? thanks! 🙂

std::string input
//get message to send to client
std::cout << "Enter message to send (type /q to quit) : ";  
getline(std::cin, input);
input += '\n';

const char *data = input.c_str();

len = strlen(data)+1;
int max_len =17;

//split msg into 16 bytes
for(int i = 0; i < len ; i+=max_len)
{
    char tempStr[max_len];
    //get next 16 bytes of msg and store
    for(int j = 0; j < max_len ; j++)
    {           
        tempStr[j] = data[j+i];
    }//end of for loop

     //Do some stuff to tempStr
}

Answer 1

In your code, the string terminator is not added. You also skip one character between the copies (since you have max_len as 17 while you only copy 16characters).

I would propose a solution using the standard library instead:

std::string::const_iterator pos = input.begin();

while (pos < input.end())
{
    // Create a temporary string containing 17 "null" characters
    char tmp[17] = {'\0' };

    // Make sure we co no copy beyond the end
    std::string::const_iterator end =
        (pos + 16 < input.end() ? pos + 16 : input.end());

    // Do the actual copying
    std::copy(pos, end, tmp);

    // Advance position
    pos += 16;

    // Use the string in 'tmp', it is properly terminated
}