lib: time: add new monotime() helpers

This adds monotime() to retrieve monotonic clock time, as well as
monotime_since() and monotime_until() for relative monotonic time.

Signed-off-by: David Lamparter <equinox@opensourcerouting.org>

2 files changed, 72 insertions, 1 deletions

diff --git a/lib/Makefile.am b/lib/Makefile.am
index f2c076c475..5dd38ee45a 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -46,7 +46,8 @@ pkginclude_HEADERS = \
 	ptm_lib.h csv.h bfd.h vrf.h ns.h systemd.h bitfield.h \
 	fifo.h memory_vty.h mpls.h imsg.h openbsd-queue.h openbsd-tree.h \
 	skiplist.h qobj.h wheel.h \
-	event_counter.h
+	event_counter.h \
+	monotime.h
 
 noinst_HEADERS = \
 	plist_int.h
diff --git a/lib/monotime.h b/lib/monotime.h
new file mode 100644
index 0000000000..10d3bb604d
--- /dev/null
+++ b/lib/monotime.h
@@ -0,0 +1,70 @@
+/*
+ * Copyright (c) 2017  David Lamparter, for NetDEF, Inc.
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#ifndef _FRR_MONOTIME_H
+#define _FRR_MONOTIME_H
+
+#include <stdint.h>
+#include <time.h>
+#include <sys/time.h>
+
+#ifndef TIMESPEC_TO_TIMEVAL
+/* should be in sys/time.h on BSD & Linux libcs */
+#define TIMESPEC_TO_TIMEVAL(tv, ts) do {	\
+	(tv)->tv_sec = (ts)->tv_sec;		\
+	(tv)->tv_usec = (ts)->tv_nsec / 1000;	\
+	} while (0)
+#endif
+
+static inline time_t monotime(struct timeval *tvo)
+{
+	struct timespec ts;
+
+	clock_gettime(CLOCK_MONOTONIC, &ts);
+	if (tvo) {
+		TIMESPEC_TO_TIMEVAL(tvo, &ts);
+	}
+	return ts.tv_sec;
+}
+
+/* the following two return microseconds, not time_t!
+ *
+ * also, they're negative forms of each other, but having both makes the
+ * code more readable
+ */
+static inline int64_t monotime_since(const struct timeval *ref,
+				     struct timeval *out)
+{
+	struct timeval tv;
+	monotime(&tv);
+	timersub(&tv, ref, &tv);
+	if (out)
+		*out = tv;
+	return (int64_t)tv.tv_sec * 1000000LL + tv.tv_usec;
+}
+
+static inline int64_t monotime_until(const struct timeval *ref,
+				     struct timeval *out)
+{
+	struct timeval tv;
+	monotime(&tv);
+	timersub(ref, &tv, &tv);
+	if (out)
+		*out = tv;
+	return (int64_t)tv.tv_sec * 1000000LL + tv.tv_usec;
+}
+
+#endif /* _FRR_MONOTIME_H */