MultiMBox.hxx

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/*
  Copyright (c) 2012, Matthew H. Reilly (kb1vc)
  All rights reserved.

  Redistribution and use in source and binary forms, with or without
  modification, are permitted provided that the following conditions are
  met:

  Redistributions of source code must retain the above copyright
  notice, this list of conditions and the following disclaimer.
  Redistributions in binary form must reproduce the above copyright
  notice, this list of conditions and the following disclaimer in
  the documentation and/or other materials provided with the
  distribution.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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  LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#ifndef MULTI_MBOX_HDR
#define MULTI_MBOX_HDR

#include <queue>
#include <vector>
#include <map>
#include <boost/thread.hpp>
#include <boost/thread/thread.hpp>
#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>

namespace SoDa {
  
  // base class for all messaging schemes. 
  class MBoxMessage {
  public:
    MBoxMessage()
    {
      reader_count = 0;
    }

    void setReaderCount(unsigned int rc)
    {
      boost::mutex::scoped_lock lock(rc_mutex);
      reader_count = rc; 
    }

    bool readyToDie() { return reader_count == 1; }
    bool decReaderCount() { return reader_count--; }

    bool free(std::queue<MBoxMessage *> & free_list) {
      boost::mutex::scoped_lock lock(rc_mutex);
      if(reader_count == 1) {
    reader_count = 0; 
    free_list.push(this); 
      }
      else {
    reader_count--;
      }
      return true;
    }

    // these are to detect "free" actions on the wrong mailbox. 
    void setMBoxTag(void * tag) { mbox_tag = tag; }
    bool checkMBoxTag(void * tag) { return mbox_tag == tag; }
    
  private:
    unsigned int reader_count;
    boost::mutex rc_mutex;
    void * mbox_tag; 
  };

  template <typename T> class MultiMBox {
  public:
    MultiMBox(bool _keep_freelist = true) {
      subscriber_count = 0;
      keep_freelist = _keep_freelist; 
    }

    int subscribe() {
      int subscriber_id = subscriber_count;
      subscriber_count++;
      subscribers[subscriber_id] = new Subscriber; 
      return subscriber_id; 
    }

    int getSubscriberCount() { return subscriber_count; }
    
    void put(T * m) {
      unsigned int i;
      m->setReaderCount(subscriber_count);
      m->setMBoxTag(this); 
      for(i = 0; i < subscriber_count; i++) {
    Subscriber * s = subscribers[i];
    boost::mutex::scoped_lock lock(s->postmutex); 
    s->posted_list.push(m);
    s->post_count++; 
    s->postcond.notify_all(); 
      }
    }

    T * get(unsigned int subscriber_id) {
      return getCommon(subscriber_id, false); 
    }

    T * getWait(unsigned int subscriber_id) {
      return getCommon(subscriber_id, true); 
    }

    void free(T * m) {
      if(m != NULL) {
    if(keep_freelist && m->checkMBoxTag(this)) {
      if(m->readyToDie()) {
        boost::mutex::scoped_lock lock(free_lock); 
        m->free(free_list);
      }
      else m->decReaderCount(); 
    }
    else {
      if(m->readyToDie()) delete m;
      else m->decReaderCount(); 
    }
      }
    }

    T * alloc()
    {
      T * ret = NULL;
      boost::mutex::scoped_lock lock(free_lock); 
      if(!free_list.empty() && keep_freelist) {
    ret = (T*) free_list.front();
    free_list.pop();
      }

      return ret; 
    }

    void addToPool(T * v) {
      if(keep_freelist) {
    boost::mutex::scoped_lock lock(free_lock); 
    free_list.push(v);
      }
    }

    unsigned int inFlightCount() {
      // go through the subscribers and find the
      // longest inflight list.
      int max_len = 0;
      int itercount = 0; 
      typename std::map<int, typename MultiMBox< T >::Subscriber * >::iterator sl; 
      for(sl = subscribers.begin();
      sl != subscribers.end();
      ++sl) {
    Subscriber * s = sl->second;
    {
      boost::mutex::scoped_lock lock(s->postmutex);
      int le = s->posted_list.size();
      itercount++; 
      // std::cerr << "multimbox list len = " << le
      //        << " iter count = " << itercount
      //        << " posted count = " << s->post_count << std::endl;
      if(le > max_len) max_len = le; 
    }
      }

      return max_len; 
    }

    bool flush(unsigned int subscriber_id) {
      T * dummy; 
      while((dummy = getCommon(subscriber_id, false)) != NULL) { 
    free(dummy);
      }
      return true; 
    }
      
    
  private:
    T * getCommon(unsigned int subscriber_id, bool wait)
    {
      if(subscriber_id >= subscriber_count) {
    // someone is asking for a message from
    // an unallocated subscriber id... throw
    // an exception.
    // or just return empty. 
    return NULL; 
      }
    
      Subscriber * s = subscribers[subscriber_id];
      boost::mutex::scoped_lock lock(s->postmutex); 
      if(s->posted_list.empty()) {
    if(!wait) {
      return NULL; 
    }
    else {
      while(s->posted_list.empty()) {
        s->postcond.wait(s->postmutex);
      }
    }
      }

      // if we get here, then we have a message.
      T * ret = NULL;
      ret = s->posted_list.front();
      s->posted_list.pop();
      s->post_count--; 
      return ret; 
    }

    unsigned int subscriber_count;
    bool keep_freelist; 

    class Subscriber {
    public:
      Subscriber() { post_count = 0; } 
      std::queue<T *> posted_list;
      int post_count; 
      boost::mutex postmutex;
      boost::condition postcond; 
    };
    std::map<int, Subscriber *> subscribers;     

    std::queue<MBoxMessage *> free_list;
    boost::mutex free_lock; 
 
  }; 
}

#endif