1 files changed, 38 insertions, 0 deletions
diff --git a/src/lib/wallclock/approx_time.c b/src/lib/wallclock/approx_time.c
new file mode 100644
index 0000000000..2528954f13
--- /dev/null
+++ b/src/lib/wallclock/approx_time.c
@@ -0,0 +1,38 @@
+/* Copyright (c) 2003, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "orconfig.h"
+#include "lib/wallclock/approx_time.h"
+
+/* =====
+ * Cached time
+ * ===== */
+
+#ifndef TIME_IS_FAST
+/** Cached estimate of the current time.  Updated around once per second;
+ * may be a few seconds off if we are really busy.  This is a hack to avoid
+ * calling time(NULL) (which not everybody has optimized) on critical paths.
+ */
+static time_t cached_approx_time = 0;
+
+/** Return a cached estimate of the current time from when
+ * update_approx_time() was last called.  This is a hack to avoid calling
+ * time(NULL) on critical paths: please do not even think of calling it
+ * anywhere else. */
+time_t
+approx_time(void)
+{
+  return cached_approx_time;
+}
+
+/** Update the cached estimate of the current time.  This function SHOULD be
+ * called once per second, and MUST be called before the first call to
+ * get_approx_time. */
+void
+update_approx_time(time_t now)
+{
+  cached_approx_time = now;
+}
+#endif /* !defined(TIME_IS_FAST) */