Tools.h++ Manual

3-4 104011 Tandem Computers Incorporated
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3.3 Common member functions
Whatever category a class might fall into, they all have very similar
programming interfaces. This section highlights the common functionality.
Persistence
The following functions are used to store an object of type ClassName to and
from an RWFile and to and from the Tools.h++ virtual streams facility and
then to restore it later:
RWFile& operator<<(RWFile& file, const
ClassName&);
RWFile& operator>>(RWFile& file, ClassName&);
RWvostream& operator<<(RWvostream& vstream,const
ClassName&);
RWvistream& operator>>(RWvistream& vstream, ClassName&);
Class RWFile encapsulates ANSI-C file I/O and is discussed in detail in
Chapter 9, “Using Class RWFile” as well as in Chapter , “Class Reference.”
Objects saved using RWFile are saved using a binary format, resulting in
efficient storage and retrieval to files.
Classes RWvistream and RWvostream are abstract base classes used by the
Tools.h++ virtual streams facility. The final output format is determined by the
specializing class. For example, RWpistream and RWpostream are two classes
that derive from RWvistream and RWvostream , respectively, that store and
retrieve objects using a “portable ASCII format”. The results can be transferred
between different operating systems. These classes are discussed in more
detail in Chapter 8, “Virtual Streams,” as well as in Chapter 21, “Class
Reference.”
It is up to the user to decide whether to store to RWFile ’s or virtual streams.
The former offers the advantage of speed, but limits portability of the results to
the host machine. The latter is not as fast, but there are specializing classes
( RWpistream and RWpostream ) that allow the results to be moved to any
machine.