Question

So I’m attempting to create a Befunge interperter and reading a text file into an array.
I’m using this code:

char map[100][100]; //not 85 x 20
//load the source
ifstream f;
f.open("file.txt", ios::in);
string s;
int i = 0;
while(f.good() && i < 100)
{
    getline(f, s);
    map[i] = s.c_str();
    i++;
}

This doesn’t work, does anyone know a way to do it without manually looping through the string?

Answer 1

Use strncpy() and specify the number of bytes:

strncpy(map[i], s.c_str(), 100);
map[i][99] = '\0'; /* this could trim s.c_str(), but at least you don't get an overflow */

instead of:

map[i] = s.c_str();

By specifying the number of bytes copied as, at most, 100, you ensure that you don’t overflow map[i]. The strncpy() function will pad map[i] with terminators, if strlen(s.c_str()) < 100. In the case where strlen(s.c_str()) >= 100, the string will be truncated in order to provide map[i] with the requisite null terminator.