std::streambuff derived class for mem optimisations

carray_streambuf.hpp

class carray_streambuf : public std::streambuf {
public:
    carray_streambuf(char *data, unsigned int len) {
        setp(data, data+len);
        setg(data, data, data + len);
    }

    // amount of stored (written!) data in bytes
    size_t saved_bytes() const { return pptr() - pbase(); }
};