2 files changed, 120 insertions, 0 deletions

diff --git a/src/xtime.c b/src/xtime.c
index dd9b60f..49d7c36 100644
--- a/src/xtime.c
+++ b/src/xtime.c
@@ -3,9 +3,11 @@
 
 #include "xtime.h"
 
+#include "alloc.h"
 #include "bfs.h"
 #include "bfstd.h"
 #include "diag.h"
+#include "sanity.h"
 
 #include <errno.h>
 #include <limits.h>
@@ -351,3 +353,98 @@ invalid:
 error:
 	return -1;
 }
+
+#if defined(_POSIX_TIMERS) && BFS_HAS_TIMER_CREATE
+#  define BFS_POSIX_TIMERS _POSIX_TIMERS
+#else
+#  define BFS_POSIX_TIMERS (-1)
+#endif
+
+struct timer {
+#if BFS_POSIX_TIMERS >= 0
+	/** The POSIX timer. */
+	timer_t timer;
+#endif
+	/** Whether to use timer_create() or setitimer(). */
+	bool legacy;
+};
+
+struct timer *xtimer_start(const struct timespec *interval) {
+	struct timer *timer = ALLOC(struct timer);
+	if (!timer) {
+		return NULL;
+	}
+
+#if BFS_POSIX_TIMERS >= 0
+	if (sysoption(TIMERS)) {
+		clockid_t clock = CLOCK_REALTIME;
+
+#if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0
+		if (sysoption(MONOTONIC_CLOCK) > 0) {
+			clock = CLOCK_MONOTONIC;
+		}
+#endif
+
+		if (timer_create(clock, NULL, &timer->timer) != 0) {
+			goto fail;
+		}
+
+		// https://github.com/llvm/llvm-project/issues/111847
+		sanitize_init(&timer->timer);
+
+		struct itimerspec spec = {
+			.it_value = *interval,
+			.it_interval = *interval,
+		};
+		if (timer_settime(timer->timer, 0, &spec, NULL) != 0) {
+			timer_delete(timer->timer);
+			goto fail;
+		}
+
+		timer->legacy = false;
+		return timer;
+	}
+#endif
+
+#if BFS_POSIX_TIMERS <= 0
+	struct timeval tv = {
+		.tv_sec = interval->tv_sec,
+		.tv_usec = (interval->tv_nsec + 999) / 1000,
+	};
+	struct itimerval ival = {
+		.it_value = tv,
+		.it_interval = tv,
+	};
+	if (setitimer(ITIMER_REAL, &ival, NULL) != 0) {
+		goto fail;
+	}
+
+	timer->legacy = true;
+	return timer;
+#endif
+
+fail:
+	free(timer);
+	return NULL;
+}
+
+void xtimer_stop(struct timer *timer) {
+	if (!timer) {
+		return;
+	}
+
+	if (timer->legacy) {
+#if BFS_POSIX_TIMERS <= 0
+		struct itimerval ival = {0};
+		int ret = setitimer(ITIMER_REAL, &ival, NULL);
+		bfs_everify(ret == 0, "setitimer()");
+#endif
+	} else {
+#if BFS_POSIX_TIMERS >= 0
+		int ret = timer_delete(timer->timer);
+		bfs_everify(ret == 0, "timer_delete()");
+#endif
+	}
+
+	free(timer);
+}
diff --git a/src/xtime.h b/src/xtime.h
index 11f2bf9..2927a2e 100644
--- a/src/xtime.h
+++ b/src/xtime.h
@@ -46,4 +46,27 @@ int xtimegm(struct tm *tm, time_t *timep);
  */
 int xgetdate(const char *str, struct timespec *result);
 
+/**
+ * A timer.
+ */
+struct timer;
+
+/**
+ * Start a timer.
+ *
+ * @interval
+ *         The regular interval at which to send SIGALRM.
+ * @return
+ *         The new timer on success, otherwise NULL.
+ */
+struct timer *xtimer_start(const struct timespec *interval);
+
+/**
+ * Stop a timer.
+ *
+ * @timer
+ *         The timer to stop.
+ */
+void xtimer_stop(struct timer *timer);
+
 #endif // BFS_XTIME_H