ostrstream();
Effects: Constructs an object of class ostrstream, initializing the base class with ostream(&sb) and initializing sb with strstreambuf().
ostrstream(char* s, int n, ios_base::openmode mode = ios_base::out);
Effects: Constructs an object of class ostrstream, initializing the base class with ostream(&sb), and initializing sb with one of two constructors:
If (mode & app) == 0, then s shall designate the first element of an array of n elements.
The constructor is strstreambuf(s, n, s).
If (mode & app) != 0, then s shall designate the first element of an array of n elements that contains an ntbs whose first element is designated by s. The constructor is strstreambuf(s, n, s + std::strlen(s)).333