Steve,

In a nutshell: FFI is dangerous ;-)
In another nutshell: FFI allows you to call functions written in other
languages (mostly C), so one can call (for instance) OS functions directly
from Squeak. Have a look at the examples, they all use functions that are
not in Squeak but live somewhere in the outside world. This of course
implies that you have to play by the rules of the outside (C) world - or in
other words, if you make a mistake you'll not drop into the debugger but
Squeak will just crash. That's what the first explanation means.

The FFI stuff is in a way related to pluggable primitives since it's using
several of the mechanisms pluggable primitives use. But there are major
differences:
* The FFI is for interfacing existing libraries only. If you don't have an
existing library that does what you want you'll have to write it - and
that's basically what the pluggable primitives are intended for.
* While it is possible to write a set of pluggable primitives that interface
existing libraries (such as the AppleScript plugin) you don't have to do it
any longer. The FFI does all the necessary conversions for you. The
AppleScript stuff could be written using the FFI without the need to have a
separate plugin for it.
* The FFI is slow compared to pluggable primitives. Since there are many
generic conversions necessary the overhead of calling C functions directly
is very high. That doesn't matter as long as you're calling functions that
actually do quite a bit of work but if you're concerned about the speed
(e.g., when you call these functions a zillion times per second) you are
much better off using pluggable primitives.
* The FFI is very platform dependent. Pluggable primitives give you a way of
defining abstract interfaces (e.g., primitives) to the provided
functionality. When using the FFI you talk to the underlying system
directly.

  Andreas

> -----Original Message-----
> From: Steve Thompson [mailto:sthompso at connertech.com]
> Sent: Monday, February 07, 2000 7:52 AM
> To: Raab, Andreas
> Subject: What Is FFI
> 
> 
> Andreas! -,
> 
> > > There is also a complete Foreign Function
> > > Interface package not described here, but with a number of useful
> > > examples in the updates.
> 
> Could you tell me, in a nutshell, what FFI is all about?  Is 
> this connected
> in some way with PluggablePrimitives?
> 
> Thanks and best regards!,
> 
> Steve Thompson
> sthompso at connertech.com
> Steve_Thompson at prodigy.net
>