From: Ben Harris <bjh21@bjh21.me.uk>
Date: Sun, 11 Nov 2018 15:54:18 +0000 (+0000)
Subject: Record the current time displayed on the dial to a file.
X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~bjharris/git?a=commitdiff_plain;h=21b459d1052a3e55f7677b008fc855256ed37a88;p=clunk.git

Record the current time displayed on the dial to a file.

This would allow for recovering from a power failure automatically, if
clunk bothered reading the file.
---

diff --git a/clunk.c b/clunk.c
index c9ad397..0ca065a 100644
--- a/clunk.c
+++ b/clunk.c
@@ -1,4 +1,5 @@
 #include <err.h>
+#include <fcntl.h>
 #include <stdbool.h>
 #include <stdio.h>
 #include <time.h>
@@ -26,6 +27,8 @@ static int const maxadvance = (10 * 3600) + (50 * 60);
 
 static struct tm displayed;
 
+static int statefd = -1;
+
 static void
 dummy_out(bool state)
 {
@@ -39,15 +42,12 @@ dummy_out(bool state)
 		fflush(stdout);
 	}
 }
-
 static void
-pulse()
+record_tick()
 {
-	struct timespec const ts = { 0, pulsewidth };
+	ssize_t ret;
+	char buf[10];
 
-	dummy_out(true);
-	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
-	dummy_out(false);
 	displayed.tm_sec += 30;
 	while (displayed.tm_sec >= 60) {
 		displayed.tm_min++;
@@ -58,9 +58,26 @@ pulse()
 		displayed.tm_min -= 60;
 	}
 	displayed.tm_hour %= 12;
-	printf(" (%d:%02d:%02d)\n",
-	       displayed.tm_hour, displayed.tm_min, displayed.tm_sec);
-	fflush(stdout);
+	sprintf(buf, "%2d:%02d:%02d\n",
+		displayed.tm_hour, displayed.tm_min, displayed.tm_sec);
+	if (statefd != -1) {
+		ret = pwrite(statefd, buf, 9, 0);
+		if (ret == -1)
+			err(1, "write to state file");
+		if (ret != 9)
+			errx(1, "short write to state file");
+	}
+}
+
+static void
+pulse()
+{
+	struct timespec const ts = { 0, pulsewidth };
+
+	dummy_out(true);
+	record_tick();
+	clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, NULL);
+	dummy_out(false);
 }
 
 static void
@@ -75,8 +92,14 @@ init(int argc, char **argv)
 	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) {
+	while ((opt = getopt(argc, argv, "f:s:")) != -1) {
 		switch (opt) {
+		case 'f':
+			statefd =
+				open(optarg, O_RDWR | O_CREAT | O_DSYNC, 0666);
+			if (statefd == -1)
+				err(1, "%s", optarg);
+			break;
 		case 's':
 			if (sscanf(optarg, "%d:%d:%d", &displayed.tm_hour,
 				   &displayed.tm_min, &displayed.tm_sec) != 3)