Using callbacks from inside the C api

[lighth7015]

Hi,

I am attempting to implement a deferred calling mechanism for an application I'm going to be writing-

Essentially, the flow goes like this-

1. C code initializes and runs scheme connection script
2. The connection script registers a list of callbacks with an intern'd C function
3. The intern'd C function records the list of callbacks and stores them in a hash map for use later on.
4. A while later, the application decides it wants to dispatch an event to the the connection script, so it invokes g_dispatch_event, which looks up the correct event and retrieves a pointer to its sexp.

However, upon invoking the sexp with the correct ctx, nothing happens. I know I'm doing something wrong, but I'm unsure what.

This is the snippet of code in question-

void g_dispatch_event(g_client_context client, kh_list_key_t state)
{	
	sexp_gc_var2(code, cref);
	khash_t(dispatcher)* dispatcher =client->dispatcher;
	
	sexp callback = kh_value(dispatcher, 
		kh_get(dispatcher, dispatcher, state));
	
	g_write_log("Address for event handler \"%s\" is %lp.", 
		state, callback );
	
	sexp_eval(client->ctx, callback, NULL);
}

Thanks in advance for the assistance!

[ashinn]

What is callback? If it's a Scheme procedure you want to use sexp_apply:

sexp_apply(client->ctx, callback, SEXP_NULL);

[lighth7015]

Yes, it is a scheme procedure; however sexp_apply doesn't even appear to be doing anything. Perhaps I'm passing in the callbacks incorrectly?

This is my scheme code:

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 																;;
;; Connection error messages											;;
;; 																;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (service-connect-failure)
	(dialog 90 0))

(define (service-connection-fail)
	(dialog 91 0))

(define (network-account-failure)
	(dialog 92 0))

(define (general-connect-failure)
	(dialog 92 0))

(define (service-connect-upgrade)
	(dialog 93 1 "Upgrade message"))

(define (service-connection-lost)
	(dialog 1 1 "Connection lost."))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 																;;
;; Connection error messages											;;
;; 																;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (service-connect-success)
	(dialog 30 2 "Connecting to the Network."))

(define (service-connection-init)
	(dialog 30 2 "Negotiating the Connection."))

(define (network-account-welcome)
	(dialog 30 2 "Connected to the Network."))

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 																;;
;; Handle connection												;;
;; 																;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
(define (service-connect-init)
	(dialog 12 0)
	(begin-connect 120
		(list ;; List of status resposnes the connection manager 
			 ;; can invoke.
			 
			 ;; Unable to resolve iv.intervue.net
			 "Can't Find Host"		service-connect-failure
			 
			 ;; For some odd reason, there aren't any SRV records
			 "Can't Auto-Discover"		service-connect-failure
			 
			 ;; The host isn't accepting TCP/IP connections.
			 "Connection Refused"		service-connect-failure
			 
			 ;; "No Route to Host"; give up connection attempt.
			 "Server Unreachable"		service-connection-fail
			 
			 ;; "No Route to Host"; give up connection attempt.
			 "Initializing Connection"	service-connection-init
			 
			 ;; Server hung up unexpectedly (or doesn't support our
			 ;; client configuration.)
			 "Service Unavailable"		service-connection-fail
			 
			 ;; TCP connection succeeded, so update the stat dialog
			 "Connection Ok"		service-connect-success
			 
			 ;; Negotiating security and protocol with the network
			 "Negotiate Connection"		service-connection-init
			 
			 ;; Okay, we're in like flynn!
			 "Account Auth Success"		network-account-welcome
			 
			 ;; The Global Catalog service didn't accept our 
			 ;; username/password combination.
			 "Account Auth Failure"		network-account-failure)
		
		general-connect-failure
	))

[ashinn]

sexp_apply returns the result of its computation, including any errors. You need to inspect this result and print them out if an exception is returned.