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      1 /*
      2  * libjingle
      3  * Copyright 2004--2006, 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 _RATELIMITMANAGER_H_
     29 #define _RATELIMITMANAGER_H_
     30 
     31 #include "talk/base/time.h"
     32 #include "talk/base/taskrunner.h"
     33 #include <map>
     34 
     35 namespace buzz {
     36 
     37 /////////////////////////////////////////////////////////////////////
     38 //
     39 // RATELIMITMANAGER
     40 //
     41 /////////////////////////////////////////////////////////////////////
     42 //
     43 // RateLimitManager imposes client-side rate limiting for xmpp tasks and
     44 // other events.  It ensures that no more than i events with a given name
     45 // can occur within k seconds.
     46 //
     47 // A buffer tracks the previous max_count events.  Before an event is allowed
     48 // to occur, it can check its rate limit with a call to VerifyRateLimit.
     49 // VerifyRateLimit will look up the i-th to last event and if more than
     50 // k seconds have passed since then, it will return true and update the
     51 // appropriate rate limits.  Else, it will return false.
     52 //
     53 /////////////////////////////////////////////////////////////////////
     54 
     55 class RateLimitManager {
     56  public:
     57 
     58   RateLimitManager() { };
     59   ~RateLimitManager() {
     60     for (RateLimitMap::iterator it = rate_limits_.begin();
     61          it != rate_limits_.end(); ++it) {
     62       delete it->second;
     63     }
     64   };
     65 
     66   // Checks if the event is under the defined rate limit and updates the
     67   // rate limit if so.  Returns true if it's under the rate limit.
     68   bool VerifyRateLimit(const std::string event_name, int max_count,
     69                        int per_x_seconds);
     70 
     71   // Checks if the event is under the defined rate limit and updates the
     72   // rate limit if so *or* if always_update = true.
     73   bool VerifyRateLimit(const std::string event_name, int max_count,
     74                        int per_x_seconds, bool always_update);
     75 
     76  private:
     77   class RateLimit {
     78    public:
     79     RateLimit(int max, int per_x_secs) : counter_(0), max_count_(max),
     80                                          per_x_seconds_(per_x_secs) {
     81       event_times_ = new uint32[max_count_];
     82       for (int i = 0; i < max_count_; i++) {
     83         event_times_[i] = 0;
     84       }
     85     }
     86 
     87     ~RateLimit() {
     88       if (event_times_) {
     89         delete[] event_times_;
     90       }
     91     }
     92 
     93     // True iff the current time >= to the next song allowed time
     94     bool IsWithinRateLimit() {
     95       return (talk_base::TimeSince(NextTimeAllowedForCounter()) >= 0);
     96     }
     97 
     98     // Updates time and counter for rate limit
     99     void UpdateRateLimit() {
    100       event_times_[counter_] = talk_base::Time();
    101       counter_ = (counter_ + 1) % max_count_;
    102     }
    103 
    104    private:
    105 
    106     // The time at which the i-th (where i = max_count) event occured
    107     uint32 PreviousTimeAtCounter() {
    108       return event_times_[counter_];
    109     }
    110 
    111     // The time that the next event is allowed to occur
    112     uint32 NextTimeAllowedForCounter() {
    113       return PreviousTimeAtCounter() + per_x_seconds_ * talk_base::kSecToMsec;
    114     }
    115 
    116     int counter_; // count modulo max_count of the current event
    117     int max_count_; // max number of events that can occur within per_x_seconds
    118     int per_x_seconds_; // interval size for rate limit
    119     uint32* event_times_; // buffer of previous max_count event
    120   };
    121 
    122   typedef std::map<const std::string, RateLimit*> RateLimitMap;
    123 
    124   // Maps from event name to its rate limit
    125   RateLimitMap rate_limits_;
    126 
    127   // Returns rate limit for event with specified name
    128   RateLimit* GetRateLimit(const std::string event_name);
    129 
    130   // True iff the current time >= to the next song allowed time
    131   bool IsWithinRateLimit(const std::string event_name);
    132 
    133   // Updates time and counter for rate limit
    134   void UpdateRateLimit(const std::string event_name, int max_count,
    135                        int per_x_seconds);
    136 
    137 };
    138 
    139 }
    140 
    141 #endif //_RATELIMITMANAGER_H_
    142