Subj : run-time installation into the Javascript context using DLLs
To   : netscape.public.mozilla.jseng
From : Jason
Date : Fri Mar 18 2005 02:55 pm

anything seem wrong with this approach?
I have a javascript shell running under Windows that I'd like to
compile once & be done with it, and add functionality incrementally by
putting it into a DLL. It seems to work quite well, actually (the
"loaddll" function is compiled into my shell; I made a small DLL called
"jspkg" which has a registration function MyRegFunc and a single test
function jtest01 which multiplies argv[0]*argv[1] and returns the
product, MyRegFunc calls
  JS_DefineFunction(cx, obj, "jtest01", jtest01, 0, JSPROP_READONLY)
and both are exported from the DLL):

js> loaddll("jspkg","MyRegFunc")
Loading library jspkg...
Found library; locating MyRegFunc()...
calling MyRegFunc()...
int jtest01(int x,y) returns x*y
DLL jspkg registered successfully!
js> jtest01(8,33)
264


static JSBool js_loaddll(JSContext *cx, JSObject *obj, uintN argc,
jsval *argv, jsval *rval)
{
    JSString *dllname_s, *regfuncname_s;
	char *dllname, *regfuncname = "JSRegisterDLL";
	HINSTANCE hdll;
	JSREGFUNC pregfunc = NULL;
	JSBool retval;

	// syntax: loaddll(dllname [,regfuncname]);
	// dllname = name of DLL
	// regfuncname = name of registration function
	//
	// Calls regfuncname(cx,obj) within library "dllname"

	if (argc < 1 || argc > 2)
		return JS_FALSE;
	dllname_s = JS_ValueToString(cx, argv[0]);
	if (!dllname_s)
		return JS_FALSE;
	dllname = JS_GetStringBytes(dllname_s);

	if (argc == 2)
	{
		regfuncname_s = JS_ValueToString(cx, argv[1]);
		if (!regfuncname_s)
			return JS_FALSE;
		regfuncname = JS_GetStringBytes(regfuncname_s);
	}

	printf("Loading library %s...\n",dllname);
	hdll = LoadLibrary(dllname);
	if (!hdll)
	{
		printf("Couldn't load library\n");
		return JS_FALSE;
	}

	printf("Found library; locating %s()...\n",regfuncname);
	pregfunc = (JSREGFUNC)GetProcAddress(hdll, regfuncname);
	if (!pregfunc)
	{
		printf("Couldn't locate registration function\n");
		return JS_FALSE;
	}
	printf("calling %s()...\n",regfuncname);
	retval = pregfunc(cx,obj);
	if (retval)
		printf("DLL %s registered successfully!\n",dllname);
	else
		printf("error registering DLL %s\n",dllname);
	return retval;
}

.