Allow the user to disable interval support at compilation time

Some users only need plain timeouts.  They shouldn't have to pay the
overhead for a field they will never set.  With this patch, they can
define TIMEOUT_DISABLE_INTERVALS and turn off the feature at compile
time.

timeout.c

@@ -44,6 +44,15 @@
 #endif
 
 
+#ifndef TIMEOUT_INT
+#define TIMEOUT_INT 0
+#define INTERVAL_GET(to) (abort(), 1)
+#define INTERVAL_SET(to, val) abort()
+#else
+#define INTERVAL_GET(to) ((to)->interval)
+#define INTERVAL_SET(to, val) ((to)->interval = (val))
+#endif
+
 /*
  * A N C I L L A R Y  R O U T I N E S
  *
@@ -337,20 +346,21 @@ static void timeouts_sched(struct timeouts *T, struct timeout *to, timeout_t exp
 
 
 static void timeouts_readd(struct timeouts *T, struct timeout *to) {
-	to->expires += to->interval;
+	const timeout_t interval = INTERVAL_GET(to);
+	to->expires += interval;
 
 	if (to->expires <= T->curtime) {
 		if (to->expires < T->curtime) {
 			timeout_t n = T->curtime - to->expires;
-			timeout_t q = n / to->interval;
-			timeout_t r = n % to->interval;
+			timeout_t q = n / interval;
+			timeout_t r = n % interval;
 
 			if (r)
-				to->expires += (to->interval * q) + (to->interval - r);
+				to->expires += (interval * q) + (interval - r);
 			else
-				to->expires += (to->interval * q);
+				to->expires += (interval * q);
 		} else {
-			to->expires += to->interval;
+			to->expires += interval;
 		}
 	}
 
@@ -360,7 +370,7 @@ static void timeouts_readd(struct timeouts *T, struct timeout *to) {
 
 TIMEOUT_PUBLIC void timeouts_add(struct timeouts *T, struct timeout *to, timeout_t timeout) {
 	if (to->flags & TIMEOUT_INT)
-		to->interval = MAX(1, timeout);
+		INTERVAL_SET(to, MAX(1, timeout));
 
 	if (to->flags & TIMEOUT_ABS)
 		timeouts_sched(T, to, timeout);
@@ -529,7 +539,7 @@ TIMEOUT_PUBLIC struct timeout *timeouts_get(struct timeouts *T) {
 		TAILQ_REMOVE(&T->expired, to, tqe);
 		to->pending = 0;
 
-		if ((to->flags & TIMEOUT_INT) && to->interval > 0) {
+		if ((to->flags & TIMEOUT_INT) && INTERVAL_GET(to) > 0) {
 			timeouts_readd(T, to);
 		} else {
 			to->timeouts = 0;

timeout.h

@@ -99,7 +99,9 @@ struct timeout_cb {
  *
  * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
 
+#ifndef TIMEOUT_DISABLE_INTERVALS
 #define TIMEOUT_INT 0x01 /* interval (repeating) timeout */
+#endif
 #define TIMEOUT_ABS 0x02 /* treat timeout values as absolute */
 
 #define TIMEOUT_INITIALIZER(flags) { (flags) }
@@ -112,8 +114,10 @@ struct timeout_cb {
 struct timeout {
 	int flags;
 
+#ifndef TIMEOUT_DISABLE_INTERVALS
 	timeout_t interval;
 	/* timeout interval if periodic */
+#endif
 
 	timeout_t expires;
 	/* absolute expiration time */