/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set et sw=2 ts=2: */
/***************************************************************************
 *            connectionpool.h
 *
 *  Wed Dec 16 12:20:44 CET 2009
 *  Copyright 2009 Bent Bisballe Nyeng
 *  deva@aasimon.org
 ****************************************************************************/

/*
 *  This file is part of Pracro.
 *
 *  Pracro is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  Pracro is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with Pracro; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.
 */
#ifndef __PRACRO_CONNECTIONPOOL_H__
#define __PRACRO_CONNECTIONPOOL_H__

#include <list>

#include "mutex.h"
#include "semaphore.h"

template <class T>
class ConnectionPool {
public:
  void add(T t);
  void remove(T t);

  bool testFree(T t);
  int numFree();

  T borrow();
  void giveBack(T t);

private:
  bool contains(std::list<T> &list, T t);

  Semaphore semaphore;
  Mutex mutex;
  std::list<T> active;
  std::list<T> passive;
};

template <class T>
class AutoBorrower {
public:
  AutoBorrower(ConnectionPool<T> &pool);
  ~AutoBorrower();

  T get();

private:
  ConnectionPool<T> &pool;
  T t;
};


//
// Implementation is below
//

template <class T>
void ConnectionPool<T>::add(T t)
{
  mutex.lock();
  passive.push_back(t);
  semaphore.post();
  mutex.unlock();
}

template <class T>
bool ConnectionPool<T>::contains(std::list<T> &list, T t)
{
  typename std::list<T>::iterator i = list.begin();
  while(i != list.end()) {
    if(*i == t) return true;
    i++;
  }

  return false;
}

template <class T>
void ConnectionPool<T>::remove(T t)
{
  mutex.lock();
  if(contains(passive, t)) {
    semaphore.post();
    passive.remove(t);
  }
  mutex.unlock();
}

template <class T>
bool ConnectionPool<T>::testFree(T t)
{
  bool testfree = false;

  mutex.lock();
  testfree = contains(passive, t);
  mutex.unlock();

  return testfree;
}

template <class T>
int ConnectionPool<T>::numFree()
{
  int num;
  mutex.lock();
  num = passive.size();
  mutex.unlock();
  return num;
}

template <class T>
T ConnectionPool<T>::borrow()
{
  T t = NULL;

  semaphore.wait();

  mutex.lock();

  t = passive.front();
  passive.remove(t);
  active.push_back(t);

  mutex.unlock();

  return t;
}

template <class T>
void ConnectionPool<T>::giveBack(T t)
{
  mutex.lock();

  if(contains(active, t)) {
    active.remove(t);
    passive.push_back(t);
    semaphore.post();
  }

  mutex.unlock();
}


template <class T>
AutoBorrower<T>::AutoBorrower(ConnectionPool<T> &p)
  : pool(p)
{
  t = pool.borrow();
}

template <class T>
AutoBorrower<T>::~AutoBorrower()
{
  pool.giveBack(t);
}

template <class T>
T AutoBorrower<T>::get()
{
  return t;
}

#endif/*__PRACRO_CONNECTIONPOOL_H__*/