Fun (system foreign) / D-Bus / oFono hacking

Fun (system foreign) / D-Bus / oFono hacking

[Neil Jerram]

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Just in case anyone else is interested in these areas...  I had a really
fun time today using the dynamic FFI to hack up Guile code to access
oFono's D-Bus API.  It's really great to be able to do this, even if it
might be more efficient in the long run to write a proper C binding.

I've attached the extremely-thrown-together code below.  Obviously it
ought to evolve (at least) into a more generic D-Bus module, and an
oFono-specific module that uses that, but right now I'm just playing...

      Neil



[-- Attachment #2: dbus.scm --]
[-- Type: text/plain, Size: 4495 bytes --]



(use-modules (system foreign)
	     (rnrs bytevectors))


(define gobject (dynamic-link "libgobject-2.0"))
(define glib (dynamic-link "libglib-2.0"))
(define gio (dynamic-link "libgio-2.0"))

(write gobject)
(newline)
(write glib)
(newline)
(write gio)
(newline)

(dynamic-call "g_type_init" gobject)

(define FALSE 0)
(define TRUE 1)

(define g_main_loop_new
  (pointer->procedure '*
		      (dynamic-func "g_main_loop_new" glib)
		      (list '* int)))

(define loop (g_main_loop_new %null-pointer FALSE))

(write loop)
(newline)

(define g_dbus_proxy_new_for_bus_sync
  (pointer->procedure '*
		      (dynamic-func "g_dbus_proxy_new_for_bus_sync" gio)
		      (list int		; bus type
			    int		; flags
			    '*		; interface info
			    '*		; bus name
			    '* 		; object path
			    '*		; interface name
			    '*		; cancellable
			    '*		; error
			    )))


;; bus type
(define G_BUS_TYPE_SYSTEM 1)
(define G_BUS_TYPE_SESSION 2)

;; flags
(define G_DBUS_PROXY_FLAGS_NONE 0)

(define manager-proxy
  (g_dbus_proxy_new_for_bus_sync G_BUS_TYPE_SYSTEM
				 G_DBUS_PROXY_FLAGS_NONE
				 %null-pointer
				 (string->pointer "org.ofono")
				 (string->pointer "/")
				 (string->pointer "org.ofono.Manager")
				 %null-pointer
				 %null-pointer))

(write manager-proxy)
(newline)

(define g_dbus_proxy_call_sync
  (pointer->procedure '*
		      (dynamic-func "g_dbus_proxy_call_sync" gio)
		      (list '*		; proxy
			    '*		; method_name
			    '*		; parameters
			    int		; flags
			    int		; timeout_msec
			    '*		; cancellable
			    '*		; error
			    )))

(define return-parms (g_dbus_proxy_call_sync manager-proxy
					     (string->pointer "GetModems")
					     %null-pointer
					     0
					     1000
					     %null-pointer
					     %null-pointer))

(define g_variant_get_child_value
  (pointer->procedure '*
		      (dynamic-func "g_variant_get_child_value" glib)
		      (list '*		; variant
			    int		; index
			    )))

(define g_variant_print
  (pointer->procedure '*
		      (dynamic-func "g_variant_print" glib)
		      (list '*		; variant
			    int		; type annotate
			    )))

(define g_variant_get_type
  (pointer->procedure '*
		      (dynamic-func "g_variant_get_type" glib)
		      (list '*		; variant
			    )))

(define g_variant_get_string
  (pointer->procedure '*
		      (dynamic-func "g_variant_get_string" glib)
		      (list '*		; variant
			    '*		; length
			    )))

(define (print-variant variant)
  (if (null-pointer? variant)
      (display "(null variant pointer)")
      (begin
	(display (pointer->string (g_variant_get_type variant)))
	(display ": ")
	(display (pointer->string (g_variant_print variant FALSE)))))
  (newline))

(print-variant return-parms)

(define modems (g_variant_get_child_value return-parms 0))
(print-variant modems)

(define first-modem (g_variant_get_child_value modems 0))
(print-variant first-modem)

(define modem-name (g_variant_get_child_value first-modem 0))
(print-variant modem-name)

(define modem-name-string
  (pointer->string (g_variant_get_string modem-name %null-pointer)))
(format #t "First modem's name is ~a\n" modem-name-string)

(define modem-proxy
  (g_dbus_proxy_new_for_bus_sync G_BUS_TYPE_SYSTEM
				 G_DBUS_PROXY_FLAGS_NONE
				 %null-pointer
				 (string->pointer "org.ofono")
				 (string->pointer modem-name-string)
				 (string->pointer "org.ofono.Modem")
				 %null-pointer
				 %null-pointer))

(write modem-proxy)
(newline)

(define g_variant_new_string
  (pointer->procedure '*
		      (dynamic-func "g_variant_new_string" glib)
		      (list '*		; string
			    )))

(define g_variant_new_boolean
  (pointer->procedure '*
		      (dynamic-func "g_variant_new_boolean" glib)
		      (list int		; boolean
			    )))

(define g_variant_new_tuple
  (pointer->procedure '*
		      (dynamic-func "g_variant_new_tuple" glib)
		      (list '*		; GVariant **
			    int		; num children
			    )))

(define powered (g_variant_new_string (string->pointer "Powered")))
(print-variant powered)
(define true (g_variant_new_boolean TRUE))
(print-variant true)

(define bv (uint-list->bytevector (map pointer-address
				       (list powered true))
				  (native-endianness)
				  (sizeof '*)))
(write bv)
(newline)

(define parms (g_variant_new_tuple (bytevector->pointer bv) 2))
(print-variant parms)

(define return-parms
  (g_dbus_proxy_call_sync modem-proxy
			  (string->pointer "SetProperty")
			  parms
			  0
			  1000
			  %null-pointer
			  %null-pointer))

(print-variant return-parms)

Re: Fun (system foreign) / D-Bus / oFono hacking

[Ludovic Courtès]

Hi Neil!

It looks like fun, and it’s great that the FFI allows for quick &
fruitful experiments like this.

Thanks,
Ludo’.