1 files changed, 65 insertions, 0 deletions
diff --git a/lib/timer.c b/lib/timer.c
new file mode 100644
index 0000000..210c726
--- /dev/null
+++ b/lib/timer.c
@@ -0,0 +1,65 @@
+/*
+ * Please, don't add this file to libcommon because timers requires
+ * -lrt on systems with old libc (and probably also -lpthread for static
+ *  build).
+ */
+#include <time.h>
+#include <signal.h>
+#include <sys/time.h>
+
+#include "c.h"
+#include "timer.h"
+
+/*
+ * Note the timeout is used for the first signal, then the signal is send
+ * repeatedly in interval ~1% of the original timeout to avoid race in signal
+ * handling -- for example you want to use timer to define timeout for a
+ * syscall:
+ *
+ *	 setup_timer()
+ *	 syscall()
+ *	 cancel_timer()
+ *
+ * if the timeout is too short than it's possible that the signal is delivered
+ * before application enter the syscall function. For this reason timer send
+ * the signal repeatedly.
+ *
+ * The applications need to ensure that they can tolerate multiple signal
+ * deliveries.
+ */
+int setup_timer(timer_t * t_id, struct itimerval *timeout,
+		void (*timeout_handler)(int, siginfo_t *, void *))
+{
+	time_t sec = timeout->it_value.tv_sec;
+	long usec = timeout->it_value.tv_usec;
+	struct sigaction sig_a;
+	static struct sigevent sig_e = {
+		.sigev_notify = SIGEV_SIGNAL,
+		.sigev_signo = SIGALRM
+	};
+	struct itimerspec val = {
+		.it_value.tv_sec = sec,
+		.it_value.tv_nsec = usec * 1000,
+		.it_interval.tv_sec = sec / 100,
+		.it_interval.tv_nsec = (sec ? sec % 100 : 1) * 10*1000*1000
+	};
+
+	if (sigemptyset(&sig_a.sa_mask))
+		return 1;
+
+	sig_a.sa_flags = SA_SIGINFO;
+	sig_a.sa_sigaction = timeout_handler;
+
+	if (sigaction(SIGALRM, &sig_a, NULL))
+		return 1;
+	if (timer_create(CLOCK_MONOTONIC, &sig_e, t_id))
+		return 1;
+	if (timer_settime(*t_id, 0, &val, NULL))
+		return 1;
+	return 0;
+}
+
+void cancel_timer(timer_t *t_id)
+{
+	timer_delete(*t_id);
+}