Simplify timespec handling; timeout.

1 files changed, 36 insertions, 6 deletions

diff --git a/norns_shell.c b/norns_shell.c
index 10f10b0..386596e 100644
--- a/norns_shell.c
+++ b/norns_shell.c
@@ -11,6 +11,23 @@
 
 #define MAX_LINE 1024
 
+#define S(n) (1000000000 * ((long) n))
+#define MS(n) (1000000 * ((long) n))
+
+#define SENTINEL_TIMEOUT (MS(1500))
+#define SENTINEL_DELAY (MS(200))
+
+int timespec_diff_gt(struct timespec *before, struct timespec *after, long ns)
+{
+	/* be careful not to overflow the long... */
+	long ss = ns / S(1) + 1;
+	long ss_diff = after->tv_sec - before->tv_sec;
+	if (ss_diff > ss)
+		return 1;
+	long ns_diff = ss_diff * S(1) + (after->tv_nsec - before->tv_nsec);
+	return ns_diff > ns;
+}
+
 int killed = 0;
 void handle_signal(int sig_num)
 {
@@ -85,8 +102,12 @@ int main (int argc, char **argv)
 	   -- as a sentinel -- repeatedly until we get the corresponding
 	   <ok>.
 	*/
-	/* TODO: time out after three seconds or something. */
 	int received = 0;
+	struct timespec began = {0};
+	if (clock_gettime(CLOCK_MONOTONIC, &began)) {
+		fprintf(stderr, "Can't use the clock? %m\n");
+		goto error;
+	}
 	struct timespec sent_sentinel = {0};
 
 	/* we'll also wait for one message after EOF... */
@@ -131,16 +152,25 @@ int main (int argc, char **argv)
 			/* If we can write, see if there's a full line. */
 			if (poll_s.revents & NN_POLLOUT) {
 				if (!received) {
-					/* only do this five times a second... */
 					struct timespec now = {0};
 					if (clock_gettime(CLOCK_MONOTONIC, &now)) {
 						fprintf(stderr, "Can't use the clock? %m\n");
 						goto error;
 					}
-					/* first bit syncs with the clock... */
-					if ((now.tv_sec - sent_sentinel.tv_sec <= 1)
-					    && (now.tv_nsec - sent_sentinel.tv_nsec
-						<= (1000000000 / 5)))
+					/* if we've been waiting on sentinel response and
+					   haven't gotten anything, time out. */
+					if (timespec_diff_gt(&began, &now, SENTINEL_TIMEOUT)) {
+						fprintf(stderr,
+							"# timed out.\n"
+							"# are you sure there's something "
+							"listening at %s?\n",
+							endpoint);
+						goto error;
+					}
+					/* only do this once every SENTINEL_DELAY... */
+					if (!timespec_diff_gt(&sent_sentinel,
+							      &now,
+							      SENTINEL_DELAY))
 						break;
 					memcpy(&sent_sentinel, &now, sizeof(struct timespec));