writing directly to std::string internal buffers

Question

I was looking for a way to stuff some data into a string across a DLL boundary. Because we use different compilers, all our dll interfaces are simple char*.

Is ther

Answer 1

You can use char buffer allocated in unique_ptr instead vector:

// allocate buffer
auto buf = std::make_unique(len);
// read data
FunctionInDLL(buf.get(), len);
// initialize string
std::string res { buf.get() };

You cannot write directly into string buffer using mentioned ways such as &str[0] and str.data():

#include 
#include 
#include 

int main()
{
    std::string str;
    std::stringstream ss;
    ss << "test string";
    ss.write(&str[0], 4);       // doesn't working
    ss.write(str.data(), 4);    // doesn't working
    std::cout << str << '\n';
}

Live example.