import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

media/mtransport/simpletokenbucket.cpp

@@ -0,0 +1,62 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* Original author: bcampen@mozilla.com */
+
+#include "simpletokenbucket.h"
+
+#include <stdint.h>
+
+#include "prinrval.h"
+
+namespace mozilla {
+
+SimpleTokenBucket::SimpleTokenBucket(size_t bucket_size,
+                                     size_t tokens_per_second) :
+  max_tokens_(bucket_size),
+  num_tokens_(bucket_size),
+  tokens_per_second_(tokens_per_second),
+  last_time_tokens_added_(PR_IntervalNow()) {
+}
+
+size_t SimpleTokenBucket::getTokens(size_t num_requested_tokens) {
+  // Only fill if there isn't enough to satisfy the request.
+  // If we get tokens so seldomly that we are able to roll the timer all
+  // the way around its range, then we lose that entire range of time
+  // for token accumulation. Probably not the end of the world.
+  if (num_requested_tokens > num_tokens_) {
+    PRIntervalTime now = PR_IntervalNow();
+
+    // If we roll over the max, since everything in this calculation is the same
+    // unsigned type, this will still yield the elapsed time (unless we've
+    // wrapped more than once).
+    PRIntervalTime elapsed_ticks = now - last_time_tokens_added_;
+
+    uint32_t elapsed_milli_sec = PR_IntervalToMilliseconds(elapsed_ticks);
+    size_t tokens_to_add = (elapsed_milli_sec * tokens_per_second_)/1000;
+
+    // Only update our timestamp if we added some tokens
+    // TODO:(bcampen@mozilla.com) Should we attempt to "save" leftover time?
+    if (tokens_to_add) {
+      num_tokens_ += tokens_to_add;
+      if (num_tokens_ > max_tokens_) {
+        num_tokens_ = max_tokens_;
+      }
+
+      last_time_tokens_added_ = now;
+    }
+
+    if (num_requested_tokens > num_tokens_) {
+      return num_tokens_;
+    }
+  }
+
+  num_tokens_ -= num_requested_tokens;
+  return num_requested_tokens;
+}
+
+} // namespace mozilla
+