Question

I am trying to create a c++ ostream for educational reasons. My test will be creating an ostream that acts like a ofstream would except instead of writing to a file it would write to a deque or vector container.

Answer 1

As it is for education, as you say, i will show you how i would do such a thingy. Otherwise, stringstream is really the way to go.

Sounds like you want to create a streambuf implementation that then writes to a vector / deque. Something like this (copying from another answer of me that targeted a /dev/null stream):

template<typename Ch, typename Traits = std::char_traits<Ch>,          typename Sequence = std::vector<Ch> > struct basic_seqbuf : std::basic_streambuf<Ch, Traits> {      typedef std::basic_streambuf<Ch, Traits> base_type;      typedef typename base_type::int_type int_type;      typedef typename base_type::traits_type traits_type;       virtual int_type overflow(int_type ch) {          if(traits_type::eq_int_type(ch, traits_type::eof()))              return traits_type::eof();          c.push_back(traits_type::to_char_type(ch));          return ch;      }      Sequence const& get_sequence() const {         return c;     } protected:     Sequence c; };  // convenient typedefs typedef basic_seqbuf<char> seqbuf; typedef basic_seqbuf<wchar_t> wseqbuf; 

You can use it like this:

seqbuf s; std::ostream os(&s); os << 'hello, i'm ' << 22 << ' years old' << std::endl; std::vector<char> v = s.get_sequence(); 

If you want to have a deque as sequence, you can do so:

typedef basic_seqbuf< char, char_traits<char>, std::deque<char> > dseq_buf; 

Or something similar… Well i haven’t tested it. But maybe that’s also a good thing – so if it contains still bugs, you can try fixing them.