1 files changed, 48 insertions, 0 deletions
diff --git a/src/lib/log/ratelim.h b/src/lib/log/ratelim.h
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+++ b/src/lib/log/ratelim.h
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+/* 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 */
+
+#ifndef TOR_RATELIM_H
+#define TOR_RATELIM_H
+
+#include <time.h>
+
+/* Rate-limiter */
+
+/** A ratelim_t remembers how often an event is occurring, and how often
+ * it's allowed to occur.  Typical usage is something like:
+ *
+   <pre>
+    if (possibly_very_frequent_event()) {
+      const int INTERVAL = 300;
+      static ratelim_t warning_limit = RATELIM_INIT(INTERVAL);
+      char *m;
+      if ((m = rate_limit_log(&warning_limit, approx_time()))) {
+        log_warn(LD_GENERAL, "The event occurred!%s", m);
+        tor_free(m);
+      }
+    }
+   </pre>
+
+   As a convenience wrapper for logging, you can replace the above with:
+   <pre>
+   if (possibly_very_frequent_event()) {
+     static ratelim_t warning_limit = RATELIM_INIT(300);
+     log_fn_ratelim(&warning_limit, LOG_WARN, LD_GENERAL,
+                    "The event occurred!");
+   }
+   </pre>
+ */
+typedef struct ratelim_t {
+  int rate;
+  time_t last_allowed;
+  int n_calls_since_last_time;
+} ratelim_t;
+
+#define RATELIM_INIT(r) { (r), 0, 0 }
+#define RATELIM_TOOMANY (16*1000*1000)
+
+char *rate_limit_log(ratelim_t *lim, time_t now);
+
+#endif