ffi-help: #:use-ffi-module

[Matt Wette <matt.wette@gmail.com>]

Hi All,

I am working on a ffi-helper: a program that will read in a C dot-h file and generate a Guile dot-scm file 
which defines a module to provide hooks into the associated C library.  Goal is to release something 
around Apr 2018.

With the helper interfaces are with ffi-modules.  A module is a set of C includes and C libraries.  The Scheme
interface code encapsulated in a Guile module.  If a C type is defined in the set of C includes, you will see it
in the associated Guile module.  If a C type is defined outside the set of includes, and is not included in a 
use-ffi-module declaration, then the type is expanded.  So, the ffi-module declaration has expressions to 
indicate which files should be include in the set defining the module.

Here is a ffi-module declaration for the gobject:

  mwette$ cat gobject.ffi 
  ;; gobject.ffi				-*- Scheme -*-

  (define-ffi-module (gobject)
    #:use-ffi-module (glib)
    #:pkg-config "gobject-2.0"
    #:include '("glib-object.h")
    #:inc-filter (lambda (file-spec path-spec)
  		 (string-contains path-spec "gobject/" 0))
    )

  ;; --- last line ---

To convert a dot-ffi module to dot-scm you use guild:
  mwette$ guild compile-ffi gobject.ffi

Currently not handled: varargs, long double, some function types, ...
I have some ideas for handling varargs.

But otherwise I'm getting things to compile:

  mwette$ wc {cairo,gdbm,gio,glib,gobject,libgit2,sqlite3}.ffi
      25      65     657 cairo.ffi
      14      45     371 gdbm.ffi
      10      27     218 gio.ffi
      19      47     509 glib.ffi
      11      27     265 gobject.ffi
      14      35     403 libgit2.ffi
      12      34     339 sqlite3.ffi

  mwette$ wc {cairo,gdbm,gio,glib,gobject,libgit2,sqlite3}.scm
    6629   16556  221347 cairo.scm
     747    2067   23093 gdbm.scm
   42884  109771 1554684 gio.scm
   28275   74979  887380 glib.scm
   10417   26654  349534 gobject.scm
   15702   45142  524011 libgit2.scm
    4980   14389  168532 sqlite3.scm

  mwette$ ls -l {cairo,gdbm,gio,glib,gobject,libgit2,sqlite3}.scm.go
  -rw-r--r--  1 mwette  staff   657197 Sep  7 20:15 cairo.scm.go
  -rw-r--r--  1 mwette  staff   105509 Sep  7 20:15 gdbm.scm.go
  -rw-r--r--  1 mwette  staff  7313669 Sep  7 20:07 gio.scm.go
  -rw-r--r--  1 mwette  staff  3168869 Sep  7 19:03 glib.scm.go
  -rw-r--r--  1 mwette  staff  1672685 Sep  7 18:43 gobject.scm.go
  -rw-r--r--  1 mwette  staff  2018653 Sep  7 20:17 libgit2.scm.go
  -rw-r--r--  1 mwette  staff   766205 Sep  7 20:17 sqlite3.scm.go

Matt