This document provides reference information for the PWLib C++ class library. It is not intended as a tutorial document.
Last updated 17 May, 2004
Copyright (C) 1999-2003 Equivalence Pty Ltd, All right reserved
Portions Copyright (C) 2004 Post Increment, All Rights Reserved
PWLib is a moderately large C++ class library that originated many years ago as a method to produce applications that run on both Microsoft Windows and Unix X-Windows systems. It also was to have a Macintosh port as well, but this never eventuated.
Since then, the availability of multi-platform GUI toolkits such as KDE and wxWindows, and the development of the OpenH323 project as primary user of the library, has emphasised the focus on networking, I/O portability, multi-threading and portability. Mostly, the library is used to create high performance and highly portable network-centric applications.
In addition to these high level functions, basic "container" classes such as arrays, linear lists, sorted lists (RB Tree) and dictionaries (hash tables) are available. These were created before the emergence of STL as a standard, so unfortunately these constructs are incompatible with iterators and generic algorithms. Development continues in this area, and future versions of PWLIB will see increased use of, and compatibility with, STL
The library is used extensively by many companies for both commercial and Open Source products. The motivation in making PWLib available as Open Source was primarily to support the OpenH323 project, but it is definitely useful as a stand-alone library.
The classes within PWLib are seperated into two types: Base Classes and Console Components The Base Classes contain all of the essential support for constructs such as containers, threads and sockets that are dependent on platform specific features. All PWLib programs will require the Base Classes
The Console Components implement functionality that is usually platform independent, and may not be required for all programs. On some platforms (notably Windows) the Base Classes and Console Components may be divided into discrete library archives. Other platforms (notably Unix platforms) combine all of the code into a single library and rely on the linker to omit code that is not required.
Note that previous versions of PWLib also contained GUI classes and GUI components, but support for these classes has been discontinued.
Tutorial introductions for PWLib are available elsewhere (see http://toncar.cz/openh323/tut), but some information on how to create a simple program is always useful.
Here is the canonical "Hello world!" program written using the PWLib infrastructure.
// hello.cxx
#include <ptlib.h>
class Hello : public PProcess
{
PCLASSINFO(Hello, PProcess)
public:
void Main();
};
PCREATE_PROCESS(Hello)
void Hello::Main()
{
cout << "Hello world!\n";
}
// End of hello.cxx
The PCREATE_PROCESS macro actually defines the main()# function and creates an instance of Hello. This assures that everything is initialised in the correct order. C++ does initialisation of global statics badly (and destruction is even worse), so try to put everything into your PProcess descedent rather than globals.
Classes that perform general I/O using the PChannel abstraction
Implementation of a network sockets abstraction (roughly based on Berkeley sockets)
Classes that handle processes, multi-threading and synchronsiation.
Implementation of the HTTP protocol
Implementation of various Internet-related protocols. Some of these are implemented within PWLib - some require external libraries for support
1.6.1