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-rw-r--r--media/mtransport/simpletokenbucket.cpp62
1 files changed, 62 insertions, 0 deletions
diff --git a/media/mtransport/simpletokenbucket.cpp b/media/mtransport/simpletokenbucket.cpp
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+/* -*- 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
+