simpletokenbucket.cpp (2075B)
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 SimpleTokenBucket::SimpleTokenBucket(size_t bucket_size, 18 size_t tokens_per_second) 19 : max_tokens_(bucket_size), 20 num_tokens_(bucket_size), 21 tokens_per_second_(tokens_per_second), 22 last_time_tokens_added_(PR_IntervalNow()) {} 23 24 size_t SimpleTokenBucket::getTokens(size_t num_requested_tokens) { 25 // Only fill if there isn't enough to satisfy the request. 26 // If we get tokens so seldomly that we are able to roll the timer all 27 // the way around its range, then we lose that entire range of time 28 // for token accumulation. Probably not the end of the world. 29 if (num_requested_tokens > num_tokens_) { 30 PRIntervalTime now = PR_IntervalNow(); 31 32 // If we roll over the max, since everything in this calculation is the same 33 // unsigned type, this will still yield the elapsed time (unless we've 34 // wrapped more than once). 35 PRIntervalTime elapsed_ticks = now - last_time_tokens_added_; 36 37 uint32_t elapsed_milli_sec = PR_IntervalToMilliseconds(elapsed_ticks); 38 size_t tokens_to_add = (elapsed_milli_sec * tokens_per_second_) / 1000; 39 40 // Only update our timestamp if we added some tokens 41 // TODO:(bcampen@mozilla.com) Should we attempt to "save" leftover time? 42 if (tokens_to_add) { 43 num_tokens_ += tokens_to_add; 44 if (num_tokens_ > max_tokens_) { 45 num_tokens_ = max_tokens_; 46 } 47 48 last_time_tokens_added_ = now; 49 } 50 51 if (num_requested_tokens > num_tokens_) { 52 return num_tokens_; 53 } 54 } 55 56 num_tokens_ -= num_requested_tokens; 57 return num_requested_tokens; 58 } 59 60 } // namespace mozilla