1 files changed, 54 insertions, 0 deletions
diff --git a/src/lib/log/ratelim.c b/src/lib/log/ratelim.c
new file mode 100644
index 0000000000..2d276055b7
--- /dev/null
+++ b/src/lib/log/ratelim.c
@@ -0,0 +1,54 @@
+/* Copyright (c) 2003-2004, Roger Dingledine
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#include "lib/log/ratelim.h"
+#include "lib/malloc/util_malloc.h"
+
+/** If the rate-limiter <b>lim</b> is ready at <b>now</b>, return the number
+ * of calls to rate_limit_is_ready (including this one!) since the last time
+ * rate_limit_is_ready returned nonzero.  Otherwise return 0.
+ * If the call number hits <b>RATELIM_TOOMANY</b> limit, drop a warning
+ * about this event and stop counting. */
+static int
+rate_limit_is_ready(ratelim_t *lim, time_t now)
+{
+  if (lim->rate + lim->last_allowed <= now) {
+    int res = lim->n_calls_since_last_time + 1;
+    lim->last_allowed = now;
+    lim->n_calls_since_last_time = 0;
+    return res;
+  } else {
+    if (lim->n_calls_since_last_time <= RATELIM_TOOMANY) {
+      ++lim->n_calls_since_last_time;
+    }
+
+    return 0;
+  }
+}
+
+/** If the rate-limiter <b>lim</b> is ready at <b>now</b>, return a newly
+ * allocated string indicating how many messages were suppressed, suitable to
+ * append to a log message.  Otherwise return NULL. */
+char *
+rate_limit_log(ratelim_t *lim, time_t now)
+{
+  int n;
+  if ((n = rate_limit_is_ready(lim, now))) {
+    if (n == 1) {
+      return tor_strdup("");
+    } else {
+      char *cp=NULL;
+      const char *opt_over = (n >= RATELIM_TOOMANY) ? "over " : "";
+      /* XXXX this is not exactly correct: the messages could have occurred
+       * any time between the old value of lim->allowed and now. */
+      tor_asprintf(&cp,
+                   " [%s%d similar message(s) suppressed in last %d seconds]",
+                   opt_over, n-1, lim->rate);
+      return cp;
+    }
+  } else {
+    return NULL;
+  }
+}