Genesis commit

1 files changed, 184 insertions, 0 deletions

diff --git a/main.c b/main.c
new file mode 100644
index 0000000..968a807
--- /dev/null
+++ b/main.c
@@ -0,0 +1,184 @@
+#include <assert.h>
+#include <err.h>
+#include <errno.h>
+#include <getopt.h>
+#include <libgen.h>
+#include <locale.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+
+#include <libintl.h>
+
+#define _(x) gettext(x)
+
+#define NSEC_PER_SEC UINT64_C(1'000'000'000)
+
+#if __APPLE__
+#define TIMER_ABSTIME (1)
+
+int clock_nanosleep(clockid_t, int, const struct timespec *, struct timespec *);
+#endif
+
+time_t syncs(time_t), syncm(time_t), synch(time_t);
+
+static void
+usage(const char *argv0, int code)
+{
+	fprintf(stderr, _("Usage: %s [-h] [-i interval] [format]\n"), argv0);
+	exit(code);
+}
+
+int
+main(int argc, char **argv)
+{
+	setlocale(LC_ALL, "");
+	bindtextdomain("messages", "./po");
+	textdomain("messages");
+
+	char interval = 's';
+	const char *argv0 = basename(argv[0]);
+	const char *dfmt = "%c", *optstr = "hi:";
+	static struct option longopts[] = {
+		{"help",     no_argument,       nullptr, 'h'},
+		{"interval", required_argument, nullptr, 'i'},
+		{nullptr,    0,                 nullptr,  0 },
+	};
+
+	for (;;) {
+		int opt = getopt_long(argc, argv, optstr, longopts, nullptr);
+		if (opt == -1)
+			break;
+
+		switch (opt) {
+		case 'h':
+			usage(argv0, EXIT_SUCCESS);
+		case 'i':
+			if (strlen(optarg) == 1) {
+				interval = *optarg;
+				if (interval == 's' || interval == 'm' || interval == 'h')
+					break;
+			}
+			errx(EXIT_FAILURE,
+				_("invalid interval ‘%s’\nRead the %s(1) manual page for valid intervals"),
+				optarg, argv0);
+		default:
+			usage(argv0, EXIT_FAILURE);
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (argc > 1)
+		usage(argv0, EXIT_FAILURE);
+	if (argc != 0)
+		dfmt = argv[0];
+
+	time_t (*sync)(time_t) =
+		  interval == 's' ? syncs
+		: interval == 'm' ? syncm
+		: interval == 'h' ? synch
+		: /* default */     syncs;
+
+	for (;;) {
+		struct timespec before, after;
+		if (clock_gettime(CLOCK_REALTIME, &before) == -1)
+			warn(_("failed to get the time"));
+
+		time_t now = time(NULL);
+		struct tm *tm = localtime(&now);
+
+		char buf[256];
+		size_t n = strftime(buf, sizeof(buf), dfmt, tm);
+		if (n == 0)
+		   	warnx(_("buffer too small"));
+		puts(buf);
+
+		if (clock_gettime(CLOCK_REALTIME, &after) == -1)
+			warn(_("failed to get the time"));
+
+		/* Duration of the clock formatting and printing */
+		struct timespec Δ = {
+			after.tv_sec  - before.tv_sec,
+			after.tv_nsec - before.tv_nsec,
+		};
+		if (Δ.tv_nsec < 0) {
+			Δ.tv_nsec += NSEC_PER_SEC;
+			Δ.tv_sec--;
+		}
+
+		struct timespec rqtp = {
+			.tv_sec  = sync(after.tv_sec),
+			.tv_nsec = 0,
+		};
+
+		int rv;
+		do
+			rv = clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &rqtp, nullptr);
+		while (rv == -1 && errno == EINTR);
+	}
+
+	/* We should never get here */
+	return EXIT_FAILURE;
+}
+
+time_t
+syncs(time_t n)
+{
+	return n + 1;
+}
+
+time_t
+syncm(time_t n)
+{
+	return n + 60 - n%60;
+}
+
+time_t
+synch(time_t n)
+{
+	return n + 3600 - n%3600;
+}
+
+#if __APPLE__
+
+int
+clock_nanosleep(clockid_t clock_id, int flags, const struct timespec *req,
+				struct timespec *rem)
+{
+	/* The rest not implemented */
+	assert(flags == TIMER_ABSTIME);
+
+	struct timespec now, Δ;
+
+	if (clock_gettime(clock_id, &now) != 0)
+		return errno;
+
+	Δ.tv_sec = req->tv_sec - now.tv_sec;
+	Δ.tv_nsec = req->tv_nsec - now.tv_nsec;
+
+	if (Δ.tv_sec < 0) {
+		Δ.tv_sec  = 0;
+		Δ.tv_nsec = 0;
+		goto out;
+	}
+
+	if (Δ.tv_nsec < 0) {
+		if (Δ.tv_sec == 0) {
+			Δ.tv_sec  = 0;
+			Δ.tv_nsec = 0;
+			goto out;
+		}
+
+		Δ.tv_sec--;
+		Δ.tv_nsec += NSEC_PER_SEC;
+	}
+
+out:
+	return nanosleep(&Δ, rem);
+}
+
+#endif