1 files changed, 118 insertions, 0 deletions
diff --git a/sleep-until.c b/sleep-until.c
new file mode 100644
index 0000000..88124ac
--- /dev/null
+++ b/sleep-until.c
@@ -0,0 +1,118 @@
+/* See LICENSE file for copyright and license details. */
+#include <sys/timerfd.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+
+int
+main(int argc, char *argv[])
+{
+	char *argv0;
+	char float_part[10];
+	struct itimerspec value;
+	struct itimerspec largest_value;
+	int i, fd = -1, clocks = 0;
+	uint64_t overrun;
+	int clockid = CLOCK_REALTIME;
+	const char *clockstr = "CLOCK_REALTIME";
+	char *p1, *p2, excess;
+	size_t len;
+
+	argv0 = *argv++, argc--;
+	if (*argv && **argv == '-') {
+		if (argv[0][1] == '-' && !argv[0][2]) {
+			argv++, argc--;
+		} else {
+			fprintf(stderr, "usage: %s [clock | timepoint] ...", argv0);
+			return 1;
+		}
+	}
+
+	if (!argc)
+		return 0;
+
+	memset(&value, 0, sizeof(value));
+	float_part[9] = '\0';
+	for (i = 0; i < argc; i++) {
+		p1 = argv[i];
+
+		if (strstr(p1, "CLOCK_") != p1)
+			goto parse_time;
+#define X(C)\
+		else if (!strcmp(p1, #C))\
+			clockid = C, clockstr = #C;
+#include "clocks.h"
+#undef X
+		else
+			clockid = -1, clockstr = "invalid";
+		clocks++;
+		continue;
+
+	parse_time:
+		if ((p2 = strchr(p1, '.')))
+			*p2++ = '\0';
+
+		value.it_value.tv_sec = (time_t)atoll(p1);
+
+		if (p2) {
+			len = strlen(p2);
+			memset(float_part, '0', 9 * sizeof(char));
+			excess = len > 9 ? p2[9] : '0';
+			len = len > 9 ? 9 : len;
+			memcpy(float_part + 9 - len, p2, len * sizeof(char));
+			value.it_value.tv_nsec = atol(float_part);
+			if ((excess >= '5') && (value.it_value.tv_nsec++ == 999999999L))
+				value.it_value.tv_nsec = 0, value.it_value.tv_sec++;
+		}
+
+		if (i == clocks)
+			largest_value = value;
+		else if (value.it_value.tv_sec > largest_value.it_value.tv_sec)
+			largest_value = value;
+		else if (value.it_value.tv_sec == largest_value.it_value.tv_sec)
+			if (value.it_value.tv_nsec > largest_value.it_value.tv_nsec)
+				largest_value = value;
+	}
+
+	if (clocks == argc)
+		return 0;
+
+	fd = timerfd_create(clockid, 0);
+	if (fd < 0)
+		goto fail;
+	if (timerfd_settime(fd, TFD_TIMER_ABSTIME, &largest_value, NULL))
+		goto fail;
+
+	if (clock_gettime(clockid, &(value.it_value)) == 0)
+		fprintf(stderr, "%s: sleeping until %lli.%09li (current time: %lli.%09li, clock: %s)\n",
+		        argv0, (long long int)(largest_value.it_value.tv_sec), largest_value.it_value.tv_nsec,
+		        (long long int)(value.it_value.tv_sec), value.it_value.tv_nsec, clockstr);
+  
+	for (;;) {
+		if (clock_gettime(clockid, &(value.it_value)))
+			goto fail;
+		if (value.it_value.tv_sec > largest_value.it_value.tv_sec)
+			break;
+		if (value.it_value.tv_sec == largest_value.it_value.tv_sec)
+			if (value.it_value.tv_nsec >= largest_value.it_value.tv_nsec)
+				break;
+		if (read(fd, &overrun, (size_t)8) < 8) {
+			if (errno == EINTR)
+				continue;
+			goto fail;
+		}
+	}
+
+	close(fd);
+	return 0;
+
+fail:
+	perror(argv0);
+	if (fd >= 0)
+		close(fd);
+	return 1;
+}