How to put stringstream contents into char instead string type?

Question

Every one know stringstream.str() need a string variable type to store the content of stringstream.str() into it .

I want to store the content of stringstream.str() into char variable or char array or pointer.

Is it possible to do that?

Please, write a simple example with your answer.

Answer 1

If you want to get the data into a char buffer, why not put it there immediately anyway? Here is a stream class which takes an array, determines its size, fills it with null characters (primarily to make sure the resulting string is null terminated), and then sets up an std::ostream to write to this buffer directly.

#include <iostream>
#include <algorithm>

struct membuf: public std::streambuf {
    template <size_t Size> membuf(char (&array)[Size]) {
        this->setp(array, array + Size - 1);
        std::fill_n(array, Size, 0);
    }
};

struct omemstream: virtual membuf, std::ostream {
    template <size_t Size> omemstream(char (&array)[Size]):
        membuf(array),
        std::ostream(this)
    {
    }
};

int main() {
    char   array[20];
    omemstream out(array);

    out << "hello, world";
    std::cout << "the buffer contains '" << array << "'\n";
}

Obviously, this stream buffer and stream would probably live in a suitable namespace and would be implemented in some header (there isn't much point in putting anything of it into a C++ file because all the function are templates needing to instantiated). You could also use the [deprecated] class std::ostrstream to do something similar but it is so easy to create a custom stream that it may not worth bothering.