base/callback.hh

   1 /*
   2  * Copyright (c) 2003 The Regents of The University of Michigan
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions are
   7  * met: redistributions of source code must retain the above copyright
   8  * notice, this list of conditions and the following disclaimer;
   9  * redistributions in binary form must reproduce the above copyright
  10  * notice, this list of conditions and the following disclaimer in the
  11  * documentation and/or other materials provided with the distribution;
  12  * neither the name of the copyright holders nor the names of its
  13  * contributors may be used to endorse or promote products derived from
  14  * this software without specific prior written permission.
  15  *
  16  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  17  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  18  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  19  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  20  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  21  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  22  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  26  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27  */
  28
  29 #ifndef __CALLBACK_HH__
  30 #define __CALLBACK_HH__
  31
  32 #include <list>
  33
  34 /**
  35  * Generic callback class.  This base class provides a virutal process
  36  * function that gets called when the callback queue is processed.
  37  */
  38 class Callback
  39 {
  40   public:
  41     /**
  42      * virtualize the destructor to make sure that the correct one
  43      * gets called.
  44      */
  45     virtual ~Callback() {}
  46
  47     /**
  48      * virtual process function that is invoked when the callback
  49      * queue is executed.
  50      */
  51     virtual void process() = 0;
  52 };
  53
  54 class CallbackQueue
  55 {
  56   protected:
  57     /**
  58      * Simple typedef for the data structure that stores all of the
  59      * callbacks.
  60      */
  61     typedef std::list<Callback *> queue;
  62
  63     /**
  64      * List of all callbacks.  To be called in fifo order.
  65      */
  66     queue callbacks;
  67
  68   public:
  69     /**
  70      * Add a callback to the end of the queue
  71      * @param callback the callback to be added to the queue
  72      */
  73     void add(Callback *callback)
  74     {
  75         callbacks.push_back(callback);
  76     }
  77
  78     /**
  79      * Find out if there are any callbacks in the queue
  80      */
  81     bool empty() const { return callbacks.empty(); }
  82
  83     /**
  84      * process all callbacks
  85      */
  86     void process()
  87     {
  88         queue::iterator i = callbacks.begin();
  89         queue::iterator end = callbacks.end();
  90
  91         while (i != end) {
  92             (*i)->process();
  93             ++i;
  94         }
  95     }
  96
  97     /**
  98      * clear the callback queue
  99      */
 100     void clear()
 101     {
 102         callbacks.clear();
 103     }
 104 };
 105
 106 #endif // __CALLBACK_HH__