[Libevent-users] libevent search order control

[Phil Budne]

Attached is a diff (independent of my rtsig patch) that allows you to
specify a search order for libevent methods by putting a comma
seperated list of method names in environment variable
"EVENT_METHODS", which I find more graceful than dealing with n
different EVENT_NOxxxx variables.


--- event.c.orig	2008-02-25 02:34:37.000000000 -0500
+++ event.c	2008-05-12 18:07:57.000000000 -0400
@@ -171,6 +171,7 @@
 {
 	int i;
 	struct event_base *base;
+	char *event_methods;
 
 	if ((base = calloc(1, sizeof(struct event_base))) == NULL)
 		event_err(1, "%s: calloc", __func__);
@@ -188,10 +189,39 @@
 	base->sig.ev_signal_pair[1] = -1;
 	
 	base->evbase = NULL;
-	for (i = 0; eventops[i] && !base->evbase; i++) {
-		base->evsel = eventops[i];
+	event_methods = getenv("EVENT_METHODS");
+	if (event_methods) {
+		char *mtemp = strdup(event_methods);
+		char *mp, *np;
+
+		for (mp = mtemp; mp && !base->evbase; mp = np) {
+			int found = 0;
+			const struct eventop **opp;
+
+			np = strchr(mp, ',');
+			if (np)
+				*np++ = '\0';
+			for (opp = eventops; *opp; opp++) {
+				const struct eventop *op = *opp;
+				if (op->name && strcmp(mp, op->name) == 0) {
+					base->evsel = op;
+					base->evbase = base->evsel->init(base);
+					found = 1;
+					break;
+				}
+			}
+#if 0 /* if EVENT_SHOW_METHOD env var set? */
+			if (!found)
+			    event_msgx("libevent %s not found", mp);
+#endif
 
-		base->evbase = base->evsel->init(base);
+		}
+	}
+	else {
+		for (i = 0; eventops[i] && !base->evbase; i++) {
+			base->evsel = eventops[i];
+			base->evbase = base->evsel->init(base);
+		}
 	}
 
 	if (base->evbase == NULL)