The header <sstream> defines four class templates and eight types that associate stream buffers with objects of class basic_string, as described in [string.classes].
namespace std { template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> > class basic_stringbuf; typedef basic_stringbuf<char> stringbuf; typedef basic_stringbuf<wchar_t> wstringbuf; template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> > class basic_istringstream; typedef basic_istringstream<char> istringstream; typedef basic_istringstream<wchar_t> wistringstream; template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> > class basic_ostringstream; typedef basic_ostringstream<char> ostringstream; typedef basic_ostringstream<wchar_t> wostringstream; template <class charT, class traits = char_traits<charT>, class Allocator = allocator<charT> > class basic_stringstream; typedef basic_stringstream<char> stringstream; typedef basic_stringstream<wchar_t> wstringstream; }