hello-swig

Beginner guide to Swig. SWIG is a software development tool that simplifies the task of interfacing different languages to C and C++ programs. In a nutshell, SWIG is a compiler that takes C/C++ declarations and creates the wrappers needed to access those declarations from other languages including Perl, Python, Tcl, Ruby, Guile, and Java. SWIG normally requires no modifications to existing code and can often be used to build a usable interface in only a few minutes.

Steps

1. Simple c/cpp program

Create a "c" or "cpp" program file

• ex: example.c
• Add few methods

2. SWIG interface file

Create a SWIG interface ".i" file

• ex: example.i
• Add function prototypes and variable declarations

3. SWIG command

Use swig command to generate java file

swig -java example.i

• This will generate 3 files
  1. example_wrap.c
  2. example.java
  3. exampleJNI.java

4. Create a shared lib

• compile example.c and example_wrap.c using

gcc -fPIC -I/usr/lib/jvm/java-1.8.0-openjdk-amd64/include/ -I/usr/lib/jvm/java-1.8.0-openjdk-amd64/include/linux -shared -o libexample.so example.c example_wrap.c

• This will output the shared lib libexample.so

5. Access the shared lib inside java program (client)

• Create a Java client to code access the C program
• ex: TestClient.java
• compile the java file by

javac TestClient.java

• run the program by

java -Djava.library.path=. TestClient

References

1. http://www.swig.org/Doc3.0/Introduction.html#Introduction_nn4
2. http://web.mit.edu/svn/src/swig-1.3.25/Examples/java/simple/index.html
3. https://anyline.com/news/java-c-swig-type-maps/ [advanced]