The R Project SVN R

static SEXP custom_handlers_env;

/* returns a httpd handler (closure) for a given path. As a special case

 * it can return a symbol that will be resolved in the "tools" namespace.

 * currently it allows custom handlers for paths of the form

 * /custom/<name>[/.*] where <name> must less than 64 characters long

 * and is matched against closures in tools:::.httpd.handlers.env */

static SEXP handler_for_path(const char *path) {

    if (path && !strncmp(path, "/custom/", 8)) { /* starts with /custom/ ? */

	const char *c = path + 8, *e = c;

	while (*c && *c != '/') c++; /* find out the name */

	if (c - e > 0 && c - e < 64) { /* if it's 1..63 chars long, proceed */

	    char fn[64];

	    memcpy(fn, e, c - e); /* create a local C string with the name for the install() call */

	    fn[c - e] = 0;

	    DBG(Rprintf("handler_for_path('%s'): looking up custom handler '%s'\n", path, fn));

	    /* we cache custom_handlers_env so in case it has not been loaded yet, fetch it */

	    if (!custom_handlers_env)

		custom_handlers_env = eval(install(".httpd.handlers.env"), R_FindNamespace(mkString("tools")));

	    /* we only proceed if .httpd.handlers.env really exists */

	    if (TYPEOF(custom_handlers_env) == ENVSXP) {

		SEXP cl = findVarInFrame3(custom_handlers_env, install(fn), TRUE);

		if (cl != R_UnboundValue && TYPEOF(cl) == CLOSXP) /* we need a closure */

		    return cl;

	    }

	}

    }

    DBG(Rprintf(" - falling back to default httpd\n"));

    return install("httpd");

}