RE: Question on Multithreading from C API

[Brent Fulgham <brent.fulgham@xpsystems.com>]

> One other approach is to wrap some scheme code around each request:
> 
>    (let ([v #f])
>      ... code to retrieve value ...
>      (thread
>        (lambda ()
>          (set! v ...)))
> 
> Would something like that work for you?
>

Maybe.  Since I'm in C at the point the request is being made, I'm
thinking in terms of something like this (pseudocode):

Scheme_Object* my_special_signal(int argc, Scheme_Object** argv)
{
	// Based on its first argument (which is the value returned by
	// scheme_thread), look up the appropriate condition
	// variable
	// Do the usual checking
	if (!	SCHEME_SOMETHINGP(argv[0]))
		scheme_raise_exn(blah blah);

	sRequest* req = lookup_struct(argv[0]);
	req->result = // result part of argv[1], which
			// should check exceptions, etc.
	
	pthread_condition(&done_var);	// Signal the waiter

	return scheme_void;
}

("my_special_signal" is registered as arity 2, etc.)

All code goes through this thunk:

char *e = 
      "(#%lambda (thunk) "
        "(#%with-handlers ([#%void (#%lambda (exn) (#%cons #f exn))]) "
          "(#%cons #t (thunk))))";

It seems like I should be able to modify this to call the global "signal"
method.  Unforunately, I'm not very familiar with Scheme's macro system
yet, so this may be wrong:

char* e =
	"(#%lambda (thunk) "
		"(#%my-special-signal (#%get-my-thread-id)
			"(#%with-handlers ([#%void (#%lambda (exn) (#%cons
#f exn))]) "
			"(#%cons #t (thunk)))))";
 
And "get-my-thread-id" is either already defined in MzScheme (I'll have to
check the manuals), or could be simply defined as a C function.

Does this look right?

-Brent