Line data    Source code

       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=2 et sw=2 tw=80: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
       5             :  * You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : /* Original author: bcampen@mozilla.com */
       8             : 
       9             : #include "simpletokenbucket.h"
      10             : 
      11             : #include <stdint.h>
      12             : 
      13             : #include "prinrval.h"
      14             : 
      15             : namespace mozilla {
      16             : 
      17           0 : SimpleTokenBucket::SimpleTokenBucket(size_t bucket_size,
      18           0 :                                      size_t tokens_per_second) :
      19             :   max_tokens_(bucket_size),
      20             :   num_tokens_(bucket_size),
      21             :   tokens_per_second_(tokens_per_second),
      22           0 :   last_time_tokens_added_(PR_IntervalNow()) {
      23           0 : }
      24             : 
      25           0 : size_t SimpleTokenBucket::getTokens(size_t num_requested_tokens) {
      26             :   // Only fill if there isn't enough to satisfy the request.
      27             :   // If we get tokens so seldomly that we are able to roll the timer all
      28             :   // the way around its range, then we lose that entire range of time
      29             :   // for token accumulation. Probably not the end of the world.
      30           0 :   if (num_requested_tokens > num_tokens_) {
      31           0 :     PRIntervalTime now = PR_IntervalNow();
      32             : 
      33             :     // If we roll over the max, since everything in this calculation is the same
      34             :     // unsigned type, this will still yield the elapsed time (unless we've
      35             :     // wrapped more than once).
      36           0 :     PRIntervalTime elapsed_ticks = now - last_time_tokens_added_;
      37             : 
      38           0 :     uint32_t elapsed_milli_sec = PR_IntervalToMilliseconds(elapsed_ticks);
      39           0 :     size_t tokens_to_add = (elapsed_milli_sec * tokens_per_second_)/1000;
      40             : 
      41             :     // Only update our timestamp if we added some tokens
      42             :     // TODO:(bcampen@mozilla.com) Should we attempt to "save" leftover time?
      43           0 :     if (tokens_to_add) {
      44           0 :       num_tokens_ += tokens_to_add;
      45           0 :       if (num_tokens_ > max_tokens_) {
      46           0 :         num_tokens_ = max_tokens_;
      47             :       }
      48             : 
      49           0 :       last_time_tokens_added_ = now;
      50             :     }
      51             : 
      52           0 :     if (num_requested_tokens > num_tokens_) {
      53           0 :       return num_tokens_;
      54             :     }
      55             :   }
      56             : 
      57           0 :   num_tokens_ -= num_requested_tokens;
      58           0 :   return num_requested_tokens;
      59             : }
      60             : 
      61             : } // namespace mozilla
      62             :