12.2 Formatted I/O

Here's a code segment that shows how you can use the iostream classes for formatted output into a portal.

// set up the RWPortal object, portal

  RWPortalOStream ostrm(portal);                               //1
  ostrm << "hello world" << endl;                              //2

`//1`	Set up an ostream object, which uses the *RWPortal* object `portal` for its sink of bytes. The *RWPortalOStream* makes its own copy of the portal, so you can specify a temporary object in the constructor if you like. This approach is efficient thanks to the interface-implementation design of the portal class.
`//2`	Output objects using the stream. Since the *RWPortalOStream* class is derived from *ostream, any objects that can be inserted into an ostream* can be inserted into an *RWPortalOStream*.

Building a stream for input is no more difficult than building one for output:

// set up the RWPortal object, portal

  RWPortalIStream istrm(portal);                               //1
  RWCString s;
  istrm >> s;                                                  //2

`//1`	Set up an istream object that uses the *RWPortal* object portal for its source of bytes. The *RWPortalIStream* also makes its own copy of the portal, allowing you to specify a temporary object to the constructor.
`//2`	Input objects using the stream. Since the *RWPortalIStream* class is derived from *istream, any objects that can be extracted from an istream* can be extracted from an *RWPortalIStream*.