1. Native Extensions
Served 3 Ways
Tejas Dinkar
Nilenso Software

2. about.me
•
Hi, I’m Tejas
•
Nilenso: Partner
•
twitter: tdinkar
•
github: gja

3. about.talk
•
Expect to see lots of code
•
Will have about 5 minutes for questions
•
Please laugh at my jokes!
•
Will cover C Extensions, FFI and SWIG

4. Native Extensions
•
Integrate with new libraries
•
Improve Performance of critical code
•
Write code that works across languages
•
Feel super 1337

5. Let’s talk about Python
•
Pythonista’s in the house?
•
Yes, I’m trolling you!
http://montgomeryq.blogspot.in/2011/05/random-illustration-tuesday-python-ruby.html

7. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

8. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

9. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

10. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

11. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

12. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

13. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

14. #include "Python.h"
#include "ruby.h"
!
static PyObject *python_ruby_eval(PyObject *self, PyObject *string)
{
VALUE val = rb_eval_string(PyString_AsString(string));
switch(TYPE(val)) {
case T_FIXNUM: return PyInt_FromLong(FIX2INT(val));
case T_STRING: return PyString_FromString(StringValuePtr(val));
default: return Py_None; // Can handle these cases later
}
}
!
static PyMethodDef module_functions[] = {
{ "eval", python_ruby_eval, METH_O, "Evaluate Ruby Code" },
{ NULL }
};
!
void initruby(void)
{
ruby_init();
Py_InitModule3("ruby", module_functions, "A ruby module for python.");
}

15. Require Files?
static PyObject *python_ruby_require(PyObject *self, PyObject *file)
{
rb_require(PyString_AsString(file));
return Py_True;
}

16. Congrats!

17. Common Fears
MEMORY ALLOCATION!?

18. Memory Management
•
Data_Wrap_Struct(klass, mark_cb, free_cb, *data)
•
Data_Get_Struct( VALUE, data_type, data* )

19. Common Fears

20. Portability
http://geekandpoke.typepad.com/geekandpoke/2008/05/the-history-of.html

21. string.c
void Init_String(void) {!
rb_cString = rb_define_class("String", rb_cObject);!
// ...!
rb_define_method(rb_cString, "eql?", rb_str_eql, 1);!
rb_define_method(rb_cString, "==", rb_str_equal, 1);!
// ...!
rb_define_method(rb_cString, "insert", rb_str_insert, 2);!
rb_define_method(rb_cString, "length", rb_str_length, 0);!
// ...!
}!
!
static VALUE rb_str_eql(VALUE self, VALUE str2)!
{!
if (self == str2) return Qtrue;!
if (!RB_TYPE_P(str2, T_STRING)) return Qfalse;!
return str_eql(self, str2);!
}!

22. string.c
void Init_String(void) {!
rb_cString = rb_define_class("String", rb_cObject);!
// ...!
rb_define_method(rb_cString, "eql?", rb_str_eql, 1);!
rb_define_method(rb_cString, "==", rb_str_equal, 1);!
// ...!
rb_define_method(rb_cString, "insert", rb_str_insert, 2);!
rb_define_method(rb_cString, "length", rb_str_length, 0);!
// ...!
}!
!
static VALUE rb_str_eql(VALUE str2, VALUE str2)!
{!
if (self == str2) return Qtrue;!
if (!RB_TYPE_P(str2, T_STRING)) return Qfalse;!
return str_eql(self, str2);!
}!

23. string.c
void Init_String(void) {!
rb_cString = rb_define_class("String", rb_cObject);!
// ...!
rb_define_method(rb_cString, "eql?", rb_str_eql, 1);!
rb_define_method(rb_cString, "==", rb_str_equal, 1);!
// ...!
rb_define_method(rb_cString, "insert", rb_str_insert, 2);!
rb_define_method(rb_cString, "length", rb_str_length, 0);!
// ...!
}!
!
static VALUE rb_str_eql(VALUE str2, VALUE str2)!
{!
if (self == str2) return Qtrue;!
if (!RB_TYPE_P(str2, T_STRING)) return Qfalse;!
return str_eql(self, str2);!
}!

24. C Extensions
Native Code
Ruby Aware!
Native Code
Ruby Code

25. Foreign Function Interface
Native Code
Native Aware!
Ruby Code
Ruby Code

26. Foreign Function Interface
•
A Ruby DSL
•
Works across all Ruby Implementations
•
Converts to and from C primitives for you

27. example
require 'ffi'!
!
module MyLib!
extend FFI::Library!
ffi_lib 'c'!
attach_function :puts, [:string], :int!
end!
!
MyLib.puts 'Hello, World using libc!'

28. another example
require 'ffi'!
!
module MyMathLib!
extend FFI::Library!
ffi_lib 'm'!
attach_function :pow, [:double, :double],!
:double!
end!
!
MyMathLib.pow(4, 5) # => 1024.0

29. Lots of built in types
Numbers!! ! ! ! ! Character!! ! ! ! ! Other!
:int! ! ! ! ! ! ! :char!! ! ! ! ! ! ! :pointer!
:short! ! ! ! ! ! :string!
:long!
:double!
:float!

30. Foreign Function Interface
•
Probably your best solution
•
It’s really easy
•
Do your modelling in Ruby
•
Still have to worry about GC
•
Sadly, no C++ without wrapping

31. Memory in FFI
def run_query_which_will_crash!
db_connection = MyFFIModule.database_connection("localhost")!
MyFFIModule.database_query(db_connection, "select * from users")!
end!

32. Memory in FFI
This will get GCed
def run_query_which_will_crash!
db_connection = MyFFIModule.database_connection("localhost")!
MyFFIModule.database_query(db_connection, "select * from users")!
end!

33. SWIG
•
Simplified Wrapper and Interface Generator
•
Annotate your C/C++ header files
•
It generates native extensions for languages
•
About 20 languages currently supported

34. SWIG
Ruby Code
Magic
Native Code
Python Code

35. The Magic
•
Takes an interface file
•
Auto generates code to make it work
•
For ruby, it’s a `regular’ C extension
•
For python, it’s a a .c and .py file
•
For Java it’s a JNI interface
•
Still need to do your own GC

36. The Rectangle
class Rectangle!
{!
int length;!
int breadth;!
!
public:!
Rectangle(int length, int breadth);!
int area();!
};

37. The Rectangle
#ifdef SWIG
%module shape
%{
SWIG Stuff Here
class Rectangle!
{!
int length;!
int breadth;!
!
public:!
Rectangle(int length, int breadth);!
int area();!
};
%}

38. require 'shapes'!
!
rectangle = shapes.Rectangle.new(10, 12)!
rectangle.area == 120!

39. Other Options
•
DL (Dynamic Load)
•
Fiddle(r)

40. TL;DR
•
Native Extensions are fun and easy to build
•
The three big tools
•
You want to pick FFI if you don’t maintain the lib
•
SWIG may be better if you are a maintainer

41. Thank You
super integration
wow
so extension
so native
ruby = win
wow
such easy
Many Questions?
no python
such performance