Can I get a non-const C string back from a C++ string?

Question

Const-correctness in C++ is still giving me headaches. In working with some old C code, I find myself needing to assign turn a C++ string object into a C string and assign i

Answer 1

Is it really that difficult to do yourself?

#include 
#include 

char *convert(std::string str)
{
    size_t len = str.length();
    char *buf = new char[len + 1];
    memcpy(buf, str.data(), len);
    buf[len] = '\0';
    return buf;
}

char *convert(std::string str, char *buf, size_t len)
{
    memcpy(buf, str.data(), len - 1);
    buf[len - 1] = '\0';
    return buf;
}

// A crazy template solution to avoid passing in the array length
// but loses the ability to pass in a dynamically allocated buffer
template 
char *convert(std::string str, char (&buf)[len])
{
    memcpy(buf, str.data(), len - 1);
    buf[len - 1] = '\0';
    return buf;
}

Usage:

std::string str = "Hello";
// Use buffer we've allocated
char buf[10];
convert(str, buf);
// Use buffer allocated for us
char *buf = convert(str);
delete [] buf;
// Use dynamic buffer of known length
buf = new char[10];
convert(str, buf, 10);
delete [] buf;