6 Pointers, Constraints, and Typemaps
Introduction
For most applications, SWIG's treatment of basic datatypes and pointers is enough to build an interface. However, in certain cases, it is desirable to change SWIG's treatment of particular datatypes. For example, we may want a char ** to act like a list of strings instead of a pointer. In another instance, we may want to tell SWIG that double *result is the output value of a function. Similarly, we might want to map a datatype of float[4] into a 4 element tuple. This chapter describes advanced methods for managing pointers, arrays, and complex datatypes. It also describes how you can customize SWIG to handle new kinds of objects and datatypes.
The SWIG Pointer Library
If your interface involves C pointers, chances are you will need to work with these pointers in some way or another. The SWIG pointer library provides a collection of useful methods for manipulating pointers. To ork withluding the ActiveWare Perl for Win32 port). SWIG makes extensive use of long filenames, so it is unlikely that the SWIG compiler will operate correctly under Windows 3.1 or DOS (the wrapper code generated by SWIG may compile however).
SWIG on the Power Macintosh
A Macintosh port of SWIG is also available, but is highly experimental at this time. It only works on PowerPC based Macintosh systems running System 7 or later. Modules can be compiled with the Metrowerks Code Warrior compiler, but support for other compilers is unknown. Due to the lack of command line options on the Mac, SWIG has been packaged in a Tcl/Tk interface that allows various settings and command line options to be specified with a graphical user interface. Underneath the hood, SWIG is identical to the Unix/Windows version. It recognizes the same set of options and generates identical code. Any SWIG command line option listed in this manual can be given to the Mac version under "Advanced Options" shown in the figure. At this writing, SWIG is only known to support Mac versions of Tcl/Tk. Work on Macintosh versions of Python and Perl is underway.
Click here to see a Macintosh screen shot.
Cross platform woes
While SWIG and various freely available scripting languages are supported on different platforms, developing cross platform applications with these tools is still immature and filled with pitfalls. In fact, it's probably only recommended for true masochists. Despite this, it's interesting to think about using freely available tools to provide common interfaces to C/C++ code. I believe that SWIG may help, but it is by no means a cross-platform solution by itself.
How to survive this manual
This manual was written to support the Unix version of SWIG. However, all of the main concepts and usage of SWIG also apply to the Windows and Macintosh versions. You should be forewarned that most of the examples are Unix-centric and may not compile correctly on other machines. However, most of the examples provided with the SWIG distribution have now been tested under both Unix and Windows-NT. When applicable, I will try to point out incompatibilities, but make no promises...
SWIG 1.1 - Last Modified : Mon Aug 4 10:46:50 1997
