9.1C++的基本流类体票 istream fstrstream Iostream Istream wIthassign fstream ifstream strstream stdiostream ostream streak ostream withassign ostrstream streambuf iostream init filebuf -strstreambuf stdiobuf9.1 C++的基本流类体系 ios istream ifstrstream istream_withassign ifstream streambuf filebuf strstreambuf stdiobuf iostream_init iostream fstream strstream stdiostream ostream ofstream ostream_withassign ostrstream