Since I'm going to be dealing with quite a lot of C++ code, it's interesting to know how one could use this functionality from a different programming language all in the cozy environment of one's own living room -the Eclipse IDE.
To get started, all we need is three ingredients: eclipse, SWIG and the SWIG plugin for eclipse called sKWash. For those unfamiliar with SWIG, according to their website, it is
"a software development tool that connects programs written in C and C++ with a variety of high-level programming languages."
Essentially you take some C or C++ code,
/* File : example.c */
#include
double My_variable = 3.0;
int fact(int n) {
if (n <= 1) return 1;
else return n*fact(n-1);
}
int my_mod(int x, int y) {
return (x%y);
}
char *get_time()
{
time_t ltime;
time(<ime);
return ctime(<ime);
}
write an interface file
/* example.i */
%module example
%{
/* Put header files here or function declarations like below */
extern double My_variable;
extern int fact(int n);
extern int my_mod(int x, int y);
extern char *get_time();
%}
extern double My_variable;
extern int fact(int n);
extern int my_mod(int x, int y);
extern char *get_time();
build the module, i.e. for python:
unix % swig -python example.i
unix % gcc -c example.c example_wrap.c \
-I/usr/local/include/python2.1
unix % ld -shared example.o example_wrap.o -o _example.so
We can now use the Python module as follows :
>>> import example
>>> example.fact(5)
120
>>> example.my_mod(7,3)
1
>>> example.get_time()
'Sun Feb 11 23:01:07 1996'
>>>
This however involves the command line. The advantage of sKWash is that it provides a GUI to SWIG through eclipse. An example of its usage is shown here; which can of course be extended to more complicated code such as the conversion of whole libraries e.g. with Quantlib a C++ library for quantitative finance. The library can then be used from the desired programming language.
In brief, you create two C++ projects in eclipse, one to store your main code, the other as a container for the C++ wrapper generation. Then create a Java or "target language" project you require in eclipse, this acts as the container for wrapper code for the target language. In the final stage create a sKWash project and specify the C++ wrapper generation project and the target language project. Eclipse will then generate the interface files, then build the project. The wrapper code should now be displayed in your wrapper projects.
