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