1. Introduction
SWIG (Simplified Wrapper and Interface Generator)
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SWIG is a software development tool that connects programs written in
C and C++ with a variety of high-level programming languages. SWIG is
used with different types of target languages including common
scripting languages such as Javascript, Perl, PHP, Python, Tcl and
Ruby.
SWIG is most commonly used to create high-level interpreted or
compiled programming environments, user interfaces, and as a tool for
testing and prototyping C/C++ software. SWIG is typically used to
parse C/C++ interfaces and generate the 'glue code' required for the
above target languages to call into the C/C++ code. SWIG can also
export its parse tree in the form of XML and Lisp s-expressions.
SWIG is free software and the code that SWIG generates is compatible
with both commercial and non-commercial projects.
It works by taking the declarations found in C/C++ header files and
using them to generate the wrapper code that scripting languages need
to access the underlying C/C++ code.
2. Getting Start
let’s say you have them in a file example.c
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/* File : example.c */
#include <time.h>
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);
}
- Interface file
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/* 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();
- Building a Tcl module
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swig -tcl example.i
gcc -fpic -c example.c example_wrap.c \
-I/usr/local/include
gcc -shared example.o example_wrap.o -o example.so
The swig command produces a file example_wrap.c that should be compiled and linked with the rest of the program.
Everything in the %{ ... %} block is simply copied verbatim to the resulting wrapper file created by SWIG, 类似声明，包括头文件和声明。
On most machines, C++ extension modules should be linked using the C++ compiler. For example:
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% swig -c++ -tcl example.i
% g++ -fPIC -c example.cxx
% g++ -fPIC -c example_wrap.cxx -I/usr/local/include
% g++ -shared example.o example_wrap.o -o example.so
How do I create shared libraries for Linux?
- For C:
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$ cc -fpic -c $(SRCS) $ ld -shared $(OBJS) -o module.so
- For C++:
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$ c++ -fpic -c $(SRCS) $ c++ -shared $(OBJS) -o module.so
If you are using GCC 4.x under Ubuntu and using python 2.6 try the following
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$ swig -python module.i
$ gcc -fpic -I/usr/include/python2.6 -c module_wrap.c
$ gcc -shared module_wrap.o -o module.so
- Noun interpretation
.i– SWIG interface file(a special .i or .swg suffix).wrap.cpp– wrapper function, write a special “wrapper” function that serves as the glue between the interpreter and the underlying C function
By default, an input file with the name file.i is transformed into a file file_wrap.c or file_wrap.cxx (depending on whether or not the -c++ option has been used).
Note:
(1) shared object file的名字要和SWIG中 %module 中指定的名字相符合，object file名字中可以加lib开头，不影响。如：libtclxgphy.so
key point: 文件名要和#define SWIG_init Tclbcmxgphy_Init对应。
(2) 如果module名字中带有number，需要注意采用如下方式：
load ./md5.so md5
(3) –I: 将所需头文件的地址指定，如果不指定，需要在.cpp文件中给出绝对地址