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      1 /*
      2  * libjingle
      3  * Copyright 2012, Google Inc.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions are met:
      7  *
      8  *  1. Redistributions of source code must retain the above copyright notice,
      9  *     this list of conditions and the following disclaimer.
     10  *  2. Redistributions in binary form must reproduce the above copyright notice,
     11  *     this list of conditions and the following disclaimer in the documentation
     12  *     and/or other materials provided with the distribution.
     13  *  3. The name of the author may not be used to endorse or promote products
     14  *     derived from this software without specific prior written permission.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
     17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
     19  * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     20  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     21  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
     22  * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
     23  * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
     24  * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     25  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     26  */
     27 
     28 #ifndef TALK_BASE_RATELIMITER_H_
     29 #define TALK_BASE_RATELIMITER_H_
     30 
     31 #include <stdlib.h>
     32 #include "talk/base/basictypes.h"
     33 
     34 namespace talk_base {
     35 
     36 // Limits the rate of use to a certain maximum quantity per period of
     37 // time.  Use, for example, for simple bandwidth throttling.
     38 //
     39 // It's implemented like a diet plan: You have so many calories per
     40 // day.  If you hit the limit, you can't eat any more until the next
     41 // day.
     42 class RateLimiter {
     43  public:
     44   // For example, 100kb per second.
     45   RateLimiter(size_t max, double period)
     46       : max_per_period_(max),
     47         period_length_(period),
     48         used_in_period_(0),
     49         period_start_(0.0),
     50         period_end_(period) {
     51   }
     52   virtual ~RateLimiter() {}
     53 
     54   // Returns true if if the desired quantity is available in the
     55   // current period (< (max - used)).  Once the given time passes the
     56   // end of the period, used is set to zero and more use is available.
     57   bool CanUse(size_t desired, double time);
     58   // Increment the quantity used this period.  If past the end of a
     59   // period, a new period is started.
     60   void Use(size_t used, double time);
     61 
     62   size_t used_in_period() const {
     63     return used_in_period_;
     64   }
     65 
     66   size_t max_per_period() const {
     67     return max_per_period_;
     68   }
     69 
     70  private:
     71   size_t max_per_period_;
     72   double period_length_;
     73   size_t used_in_period_;
     74   double period_start_;
     75   double period_end_;
     76 };
     77 
     78 }  // namespace talk_base
     79 
     80 #endif  // TALK_BASE_RATELIMITER_H_
     81