From: Ben Harris <bjh21@bjh21.me.uk>
Date: Sat, 3 Nov 2018 22:25:48 +0000 (+0000)
Subject: Add an option to specify the current displayed time at startup.
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=8b4058d4f93ed0908db81488623831a05f309342;p=clunk.git

Add an option to specify the current displayed time at startup.
---

diff --git a/clunk.c b/clunk.c
index f7e7271..6e6e191 100644
--- a/clunk.c
+++ b/clunk.c
@@ -2,6 +2,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <time.h>
+#include <unistd.h>
 
 static long const pulsewidth = 250000000; /* nanoseconds */
 
@@ -26,15 +27,16 @@ pulse()
 		displayed.tm_min -= 60;
 	}
 	displayed.tm_hour %= 12;
-	printf(" (%02d:%02d:%02d)\n",
+	printf(" (%d:%02d:%02d)\n",
 	       displayed.tm_hour, displayed.tm_min, displayed.tm_sec);
 	fflush(stdout);
 }
 
 static void
-init()
+init(int argc, char **argv)
 {
 	struct timespec ts;
+	int opt;
 
 	tzset();
 	if (clock_gettime(CLOCK_REALTIME, &ts) != 0)
@@ -42,30 +44,76 @@ init()
 	if (localtime_r(&ts.tv_sec, &displayed) == NULL)
 		err(1, "localtime_r");
 	displayed.tm_sec = (displayed.tm_sec >= 30) ? 30 : 0;
+	while ((opt = getopt(argc, argv, "s:")) != -1) {
+		switch (opt) {
+		case 's':
+			if (sscanf(optarg, "%d:%d:%d", &displayed.tm_hour,
+				   &displayed.tm_min, &displayed.tm_sec) != 3)
+				errx(1, "usage");
+			break;
+		}
+	}
+}
+
+enum need_adjust { STOP, TICK, ADVANCE };
+
+static enum need_adjust
+need_adjust(struct tm const *now)
+{
+	long diff;
+
+	diff = now->tm_sec - displayed.tm_sec +
+		60 * (now->tm_min - displayed.tm_min) +
+		3600 * (now->tm_hour - displayed.tm_hour);
+	if (diff < 0) diff += 3600 * 12;
+	diff %= 3600 * 12;
+	printf("diff = %ld\n", diff);
+	if (diff < 30 || diff >= (10 * 3600)) return STOP;
+	if (diff < 60) return TICK;
+	if (diff < (10 * 3600)) return ADVANCE;
+}
+
+static void
+ts_advance(struct timespec *tp, long nsec)
+{
+
+	tp->tv_nsec += nsec;
+	if (tp->tv_nsec >= 1000000000) tp->tv_sec++;
 }
-	
 
 static void
 run()
 {
 	struct timespec ts;
 	struct tm tm;
+	int tick;
 
 	while (true) {
 		if (clock_gettime(CLOCK_REALTIME, &ts) != 0)
 			err(1, "clock_gettime");
+		ts_advance(&ts, pulsewidth);
 		if (localtime_r(&ts.tv_sec, &tm) == NULL)
 			err(1, "localtime_r");
-		/* Round down to the last 30 s. */
+		tick = 30;
+		switch (need_adjust(&tm)) {
+		case ADVANCE:
+			tick = 2;
+			/* FALLTHROUGH */
+		case TICK:
+			pulse();
+			/* FALLTHROUGH */
+		case STOP:
+			/* nothing */ ;
+		}
+		/* Round down to the last tick. */
 		ts.tv_nsec = 0;
-		ts.tv_sec -= tm.tm_sec % 30;
+		ts.tv_sec -= tm.tm_sec % tick;
 		/* Choose when next tick will be. */
 		ts.tv_nsec = 1000000000 - pulsewidth;
-		ts.tv_sec += 29;
+		ts.tv_sec += tick - 1;
 		if (clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts, NULL)
 		    != 0)
 			err(1, "clock_nanosleep");
-		pulse();
 	}
 }
 
@@ -73,7 +121,7 @@ int
 main(int argc, char **argv)
 {
 
-	init();
+	init(argc, argv);
 	run();
 	return 0;
 }