UnifiedFFI - A common language for the outside world Video: https://youtu.be/418eEvCiepU Fri, August 26, 11:45am – 12:30pm First Name: Esteban Last Name: Lorenzano Email: estebanlm@gmail.com Title: UnifiedFFI - A common language for the outside world Type: Talk Abstract: UnifiedFFI is a new foreign function interface who aims to reunite the best of all previous implementations into a single common API. Developed for the new SpurVM, it keeps the simplicity of NativeBoost function calls syntax but with the backbone of the more easy to maintain FFIPlugin. Bio: Esteban Lorenzano, 44 years. Programmer since ever, Full-time Smalltalker since 2007 and Pharo enthusiast since almost its every beginning, after owning his own company and spend some years teaching at different universities in Argentina, he currently leads de development of Pharo itself, at the RMoD team of INRIA (France)

1. UnifiedFFI
A common language to talk with the outside world
Now
with dem
o!

2. Esteban Lorenzano
(The stabilisation fairy)

4. What is UnifiedFFI
• A front-end to express Foreign Function Interface (FFI)
calls in Pharo.
• Uses ThreadedFFIPlugin, but should be able to plug
others in the future.
• It shares same philosophy as NativeBoost
‣ keep as much as possible in the image
‣ no need to modify VM to add functionality
‣ But it is not ASM: Just plain Smalltalk.

5. But, what happened with
NativeBoost?
• It was not working on Spur
• It was hard to maintain (and we need a different
implementation for each architecture)
• Since we were using NB exclusively for FFI, we
decided to replace it with a different one, using
the VM plugin

6. UnifiedFFI goals
• Keep NativeBoost syntax
‣ Because is cool :)
‣ Provide backward compatibility for most uses
• Enhance documentation and self-documentation
• Be the unified base for future FFI backends
implementations

7. How does a call looks like?
char *getenv(const char *)
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
(People who know NativeBoost will find this very familiar….)

8. How does a call looks like?
char *getenv(const char *)
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
A regular Pharo method with one argument

9. How does a call looks like?
char *getenv(const char *)
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
A literal array to represent C function

10. How does a call looks like?
char *getenv(const char *)
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
Types annotation used to generate marshalling code

11. How does a call looks like?
char *getenv(const char *)
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
The value to be passed when calling out

12. How does a call looks like?
char *getenv(const char *)
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
The library to lookup C function

13. FFILibrary
• A very simple abstraction to define module
names that can be different each platform.
• Can be used also as a place to store C function
definitions (like a real library :) ).

14. FFILibrary: LibC
FFILibrary subclass: #LibC
LibC>>unixModuleName
^ ‘libc.so.6'
LibC>>macModuleName
^ ‘libc.dylib'
LibC>>win32ModuleName
^ ‘msvcrt.dll'
LibC>>memCopy: src to: dest size: n
^ self ffiCall: #(void *memcpy(void *dest, const void *src, size_t n))

15. Insights to UnifiedFFI
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC

16. Insights to UnifiedFFI
getEnv: variable
^ self
ffiCall: #( String getenv( String variable ))
module: LibC
1.Generate bytecodes for marshalling
2.Re-send the method execution
char *getenv(const char *)

17. How does a call looks like?
(bytecode version)
char *getenv(const char *)
21 <20> pushConstant: <cdecl: char* 'getenv' (char*) module: 'libc.dylib'>
22 <10> pushTemp: 0
23 <8A 81> pop 1 into (Array new: 1)
25 <E1> send: invokeWithArguments:
26 <7C> returnTop

18. Types
• Support for standard C types: int, float, etc.
• Support for type aliases (map a name to one of the defined types)
• Complex types:
• FFIExternalObject: External addresses (objects)
• FFIOpaqueObject: Opaque C types/structures
• FFIExternalStructure
• FFIExternalArray, FFITypeArray
• FFIExternalEnumeration
• FFIExternalValueHolder: Buffers (to pass referenced data, e.g. “double *”)
• FFIConstantHandle: Windows HANDLE (constant addresses)

19. FFIExternalObject (1)
AthensSurface subclass: #AthensCairoSurface
uses: TCairoLibrary
instanceVariableNames: 'handle context builder id ftFontRenderer session'
classVariableNames: ''
poolDictionaries: 'AthensCairoDefs'
package: ‘Athens-Cairo'
cairo_surface_t *
cairo_image_surface_create (cairo_format_t format,
int width,
int height);

20. FFIExternalObject (2)
AthensCairoSurface class>>primImage: aFormat width: aWidth height: aHeight
^self ffiCall: #(AthensCairoSurface cairo_image_surface_create (
int aFormat,
int aWidth,
int aHeight) )
cairo_surface_t *
cairo_image_surface_create (cairo_format_t format, int width, int height);

21. FFIExternalObject (3)
AthensCairoSurface>>getDataPtr
"get a pointer to surface bitmap data"
^self ffiCall: #( void* cairo_image_surface_get_data ( self ) )
unsigned char *
cairo_image_surface_get_data (cairo_surface_t *surface);

22. FFICallback
callback := FFICallback
signature: #(int (const void *arg1, const void *arg2))
block: [ :arg1 :arg2 |
((arg1 doubleAt: 1) - (arg2 doubleAt: 1)) sign ].
int (*compar)(const void*,const void*)

23. FFICallback
callback := FFICallback
signature: #(int (const void *arg1, const void *arg2))
block: [ :arg1 :arg2 |
((arg1 doubleAt: 1) - (arg2 doubleAt: 1)) sign ].
int (*compar)(const void*,const void*)
A literal array to represent C anonymous function

24. FFICallback: qsort
Cqsort>>primQsort: array with: count with: size with: compare
self
ffiCall: #(void qsort (FFIExternalArray array, size_t count, size_t size, FFICallback compare))
module: LibC
Cqsort>>example
| array callback |
array := FFIExternalArray newType: 'double' size: 100.
1 to: 100 do: [ :i | array at: i put: (100 atRandom asFloat) ].
callback := FFICallback
signature: #(int (const void *arg1, const void *arg2))
block: [ :arg1 :arg2 |
((arg1 doubleAt: 1) - (arg2 doubleAt: 1)) sign ].
self
primQsort: array
with: 100
with: (FFIExternalType sizeOf: ‘double’)
with: callback.

25. Status
• Feature complete (but I keep adding stuff when
requested)
• Documentation ongoing
• Still can accept a lot of optimisations (but that
will be for versions 1.x)

26. Summary
• Replace for NativeBoost keeping its philosophy
• Simple Callout/Callback system
• Very easy to extend (no need of ASM
knowledge)
• Is ready to use in Pharo 5.0

27. Thanks!
Smalltalk quitSession.