/data/refman/pasoursint/CMSSW_5_3_1/src/EventFilter/StorageManager/interface/ConcurrentQueue.h

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// $Id: ConcurrentQueue.h,v 1.13 2011/04/07 09:28:22 mommsen Exp $


#ifndef EventFilter_StorageManager_ConcurrentQueue_h
#define EventFilter_StorageManager_ConcurrentQueue_h

#include <algorithm>
#include <cstddef>
#include <exception>
#include <limits>
#include <list>

#include <iostream> // debugging

#include <boost/date_time/posix_time/posix_time_types.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/thread/condition.hpp>
#include <boost/thread/mutex.hpp>

namespace stor
{
  namespace detail
  {
    typedef size_t MemoryType;

    /*
      This template is using SFINAE to figure out if the class used to
      instantiate the ConcurrentQueue template has a method memoryUsed
      returning the number of bytes occupied by the class itself.
    */
    template <typename T>
    class hasMemoryUsed
    {
      typedef char TrueType;
      struct FalseType{ TrueType _[2]; };
      
      template <MemoryType (T::*)() const>
      struct TestConst;
      
      template <typename C>
      static TrueType test( TestConst<&C::memoryUsed>* );
      template <typename C>
      static FalseType test(...);
      
    public:
      static const bool value = (sizeof(test<T>(0)) == sizeof(TrueType));
    };
    
    template <typename T>
    MemoryType 
    memoryUsage(const std::pair<T,size_t>& t)
    {
      MemoryType usage(0UL);
      try
      {
        usage = t.first.memoryUsed();
      }
      catch(...)
      {}
      return usage;
    }
    
    template <typename T>
    typename boost::enable_if<hasMemoryUsed<T>, MemoryType>::type
    memoryUsage(const T& t)
    {
      MemoryType usage(0UL);
      try
      {
        usage = t.memoryUsed();
      }
      catch(...)
      {}
      return usage;
    }
  
    template <typename T>
    typename boost::disable_if<hasMemoryUsed<T>, MemoryType>::type
    memoryUsage(const T& t)
    { return sizeof(T); }

  }// end namespace detail

  
  template <class T>
  struct FailIfFull
  {
    typedef void ReturnType;

    typedef T ValueType;
    typedef std::list<T> SequenceType;
    typedef typename SequenceType::size_type SizeType;

    static struct QueueIsFull : public std::exception
    {
      virtual const char* what() const throw()
      {
        return "Cannot add item to a full queue";
      }
    } queueIsFull;

    static void doInsert
    (
      T const& item,
      SequenceType& elements,
      SizeType& size,
      detail::MemoryType const& itemSize,
      detail::MemoryType& used,
      boost::condition& nonempty
    )
    {
      elements.push_back(item);
      ++size;
      used += itemSize;
      nonempty.notify_one();
    }
               
    static ReturnType doEnq
    (
      T const& item,
      SequenceType& elements,
      SizeType& size,
      SizeType& capacity,
      detail::MemoryType& used,
      detail::MemoryType& memory,
      size_t& elementsDropped,
      boost::condition& nonempty
    )
    {
      detail::MemoryType itemSize = detail::memoryUsage(item);
      if (size >= capacity || used+itemSize > memory)
      {
        ++elementsDropped;
        throw queueIsFull;
      }
      else
      {
        doInsert(item, elements, size, itemSize, used, nonempty);
      }
    }         
  };


  template <class T>
  struct KeepNewest
  {
    typedef std::pair<T,size_t> ValueType;
    typedef std::list<T> SequenceType;
    typedef typename SequenceType::size_type SizeType;
    typedef SizeType ReturnType;

    static void doInsert
    (
      T const& item,
      SequenceType& elements,
      SizeType& size,
      detail::MemoryType const& itemSize,
      detail::MemoryType& used,
      boost::condition& nonempty
    )
    {
      elements.push_back(item);
      ++size;
      used += itemSize;
      nonempty.notify_one();
    }

    static ReturnType doEnq
    (
      T const& item,
      SequenceType& elements,
      SizeType& size,
      SizeType& capacity,
      detail::MemoryType& used,
      detail::MemoryType& memory,
      size_t& elementsDropped,
      boost::condition& nonempty
    )
    {
      SizeType elementsRemoved(0);
      detail::MemoryType itemSize = detail::memoryUsage(item);
      while ( (size==capacity || used+itemSize > memory) && !elements.empty() )
      {
        SequenceType holder;
        // Move the item out of elements in a manner that will not throw.
        holder.splice(holder.begin(), elements, elements.begin());
        // Record the change in the length of elements.
        --size;
        used -= detail::memoryUsage( holder.front() );
        ++elementsRemoved;
      }
      if (size < capacity && used+itemSize <= memory)
        // we succeeded to make enough room for the new element
      {
        doInsert(item, elements, size, itemSize, used, nonempty);
      }
      else
      {
        // we cannot add the new element
        ++elementsRemoved;
      }
      elementsDropped += elementsRemoved;
      return elementsRemoved;
    }
  };


  template <class T>
  struct RejectNewest
  {
    typedef std::pair<T,size_t> ValueType;
    typedef std::list<T> SequenceType;
    typedef typename SequenceType::size_type SizeType;
    typedef SizeType ReturnType;

    static void doInsert
    (
      T const& item,
      SequenceType& elements,
      SizeType& size,
      detail::MemoryType const& itemSize,
      detail::MemoryType& used,
      boost::condition& nonempty
    )
    {
      elements.push_back(item);
      ++size;
      used += itemSize;
      nonempty.notify_one();
    }

    static ReturnType doEnq
    (
      T const& item,
      SequenceType& elements,
      SizeType& size,
      SizeType& capacity,
      detail::MemoryType& used,
      detail::MemoryType& memory,
      size_t& elementsDropped,
      boost::condition& nonempty
    )
    {
      detail::MemoryType itemSize = detail::memoryUsage(item);
      if (size < capacity && used+itemSize <= memory)
      {
        doInsert(item, elements, size, itemSize, used, nonempty);
        return 0;
      }
      ++elementsDropped;
      return 1;
    }
  };

  template <class T, class EnqPolicy=FailIfFull<T> >
  class ConcurrentQueue
  {
  public:
    typedef typename EnqPolicy::ValueType ValueType;
    typedef typename EnqPolicy::SequenceType SequenceType;
    typedef typename SequenceType::size_type SizeType;

    explicit ConcurrentQueue
    (
      SizeType maxSize = std::numeric_limits<SizeType>::max(),
      detail::MemoryType maxMemory = std::numeric_limits<detail::MemoryType>::max()
    );

    ~ConcurrentQueue();

    typename EnqPolicy::ReturnType enqNowait(T const& item);

    void enqWait(T const& p);

    bool enqTimedWait(T const& p, boost::posix_time::time_duration const&);

    bool deqNowait(ValueType&);

    void deqWait(ValueType&);

    bool deqTimedWait(ValueType&, boost::posix_time::time_duration const&);

    bool empty() const;

    bool full() const;

    SizeType size() const;

    SizeType capacity() const;

    bool setCapacity(SizeType n);

    detail::MemoryType used() const;

    detail::MemoryType memory() const;

    bool setMemory(detail::MemoryType n);

    SizeType clear();

    void addExternallyDroppedEvents(SizeType);
    

  private:
    typedef boost::mutex::scoped_lock LockType;

    mutable boost::mutex protectElements_;
    mutable boost::condition queueNotEmpty_;
    mutable boost::condition queueNotFull_;

    SequenceType elements_;
    SizeType capacity_;
    SizeType size_;
    /*
      N.B.: we rely on SizeType *not* being some synthesized large
      type, so that reading the value is an atomic action, as is
      incrementing or decrementing the value. We do *not* assume that
      there is any atomic getAndIncrement or getAndDecrement
      operation.
    */
    detail::MemoryType memory_;
    detail::MemoryType used_;
    size_t elementsDropped_;

    /*
      These private member functions assume that whatever locks
      necessary for safe operation have already been obtained.
     */

    /*
      Insert the given item into the list, if it is not already full,
      and increment size. Return true if the item is inserted, and
      false if not.
    */
    bool insertIfPossible(T const& item);

    /*
      Remove the object at the head of the queue, if there is one, and
      assign item the value of this object.The assignment may throw an
      exception; even if it does, the head will have been removed from
      the queue, and the size appropriately adjusted. It is assumed
      the queue is nonempty. Return true if the queue was nonempty,
      and false if the queue was empty.
     */
    bool removeHeadIfPossible(ValueType& item);

    /*
      Remove the object at the head of the queue, and assign item the
      value of this object. The assignment may throw an exception;
      even if it does, the head will have been removed from the queue,
      and the size appropriately adjusted. It is assumed the queue is
      nonempty.
     */
    void removeHead(ValueType& item);

    void assignItem(T& item, const T& element);
    void assignItem(std::pair<T,size_t>& item, const T& element);

    /*
      Return false if the queue can accept new entries.
     */
    bool isFull() const;

    /*
      These functions are declared private and not implemented to
      prevent their use.
     */
    ConcurrentQueue(ConcurrentQueue<T,EnqPolicy> const&);
    ConcurrentQueue& operator=(ConcurrentQueue<T,EnqPolicy> const&);
  };

  //------------------------------------------------------------------
  // Implementation follows
  //------------------------------------------------------------------

  template <class T, class EnqPolicy>
  ConcurrentQueue<T,EnqPolicy>::ConcurrentQueue
  (
    SizeType maxSize,
    detail::MemoryType maxMemory
  ) :
    protectElements_(),
    elements_(),
    capacity_(maxSize),
    size_(0),
    memory_(maxMemory),
    used_(0),
    elementsDropped_(0)
  {}

  template <class T, class EnqPolicy>
  ConcurrentQueue<T,EnqPolicy>::~ConcurrentQueue()
  {
    LockType lock(protectElements_);
    elements_.clear();
    size_ = 0;
    used_ = 0;
    elementsDropped_ = 0;
  }

  template <class T, class EnqPolicy>
  typename EnqPolicy::ReturnType
  ConcurrentQueue<T,EnqPolicy>::enqNowait(T const& item)
  {
    LockType lock(protectElements_);
    return EnqPolicy::doEnq
      (item, elements_, size_, capacity_, used_, memory_,
        elementsDropped_, queueNotEmpty_);
  }

  template <class T, class EnqPolicy>
  void
  ConcurrentQueue<T,EnqPolicy>::enqWait(T const& item)
  {
    LockType lock(protectElements_);
    while ( isFull() ) queueNotFull_.wait(lock);
    EnqPolicy::doInsert(item, elements_, size_,
      detail::memoryUsage(item), used_, queueNotEmpty_);
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::enqTimedWait
  (
    T const& item, 
    boost::posix_time::time_duration const& waitTime
  )
  {
    LockType lock(protectElements_);
    if ( isFull() )
    {
      queueNotFull_.timed_wait(lock, waitTime);
    }
    return insertIfPossible(item);
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::deqNowait(ValueType& item)
  {
    LockType lock(protectElements_);
    return removeHeadIfPossible(item);
  }

  template <class T, class EnqPolicy>
  void
  ConcurrentQueue<T,EnqPolicy>::deqWait(ValueType& item)
  {
    LockType lock(protectElements_);
    while (size_ == 0) queueNotEmpty_.wait(lock);
    removeHead(item);
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::deqTimedWait
  (
    ValueType& item,
    boost::posix_time::time_duration const& waitTime
  )
  {
    LockType lock(protectElements_);
    if (size_ == 0)
    {
      queueNotEmpty_.timed_wait(lock, waitTime);
    }
    return removeHeadIfPossible(item);
  }

  template <class T, class EnqPolicy>
  bool 
  ConcurrentQueue<T,EnqPolicy>::empty() const
  {
    // No lock is necessary: the read is atomic.
    return size_ == 0;
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::full() const
  {
    LockType lock(protectElements_);
    return isFull();
  }

  template <class T, class EnqPolicy>
  typename ConcurrentQueue<T,EnqPolicy>::SizeType 
  ConcurrentQueue<T,EnqPolicy>::size() const
  {
    // No lock is necessary: the read is atomic.
    return size_;
  }

  template <class T, class EnqPolicy>
  typename ConcurrentQueue<T,EnqPolicy>::SizeType
  ConcurrentQueue<T,EnqPolicy>::capacity() const
  {
    // No lock is necessary: the read is atomic.
    return capacity_;
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::setCapacity(SizeType newcapacity)
  {
    LockType lock(protectElements_);
    bool isEmpty = (size_ == 0);
    if (isEmpty) capacity_ = newcapacity;
    return isEmpty;
  }

  template <class T, class EnqPolicy>
  detail::MemoryType 
  ConcurrentQueue<T,EnqPolicy>::used() const
  {
    // No lock is necessary: the read is atomic.
    return used_;
  }

  template <class T, class EnqPolicy>
  detail::MemoryType
  ConcurrentQueue<T,EnqPolicy>::memory() const
  {
    // No lock is necessary: the read is atomic.
    return memory_;
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::setMemory(detail::MemoryType newmemory)
  {
    LockType lock(protectElements_);
    bool isEmpty = (size_ == 0);
    if (isEmpty) memory_ = newmemory;
    return isEmpty;
  }

  template <class T, class EnqPolicy>
  typename ConcurrentQueue<T,EnqPolicy>::SizeType
  ConcurrentQueue<T,EnqPolicy>::clear()
  {
    LockType lock(protectElements_);
    SizeType clearedEvents = size_;
    elementsDropped_ += size_;
    elements_.clear();
    size_ = 0;
    used_ = 0;
    return clearedEvents;
  }
  
  template <class T, class EnqPolicy>
  void 
  ConcurrentQueue<T,EnqPolicy>::addExternallyDroppedEvents(SizeType n)
  {
    LockType lock(protectElements_);
    elementsDropped_ += n;
  }

  //-----------------------------------------------------------
  // Private member functions
  //-----------------------------------------------------------

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::insertIfPossible(T const& item)
  {
    if ( isFull() )
    {
      ++elementsDropped_;
      return false;
    }
    else
    {
      EnqPolicy::doInsert(item, elements_, size_,
      detail::memoryUsage(item), used_, queueNotEmpty_);
      return true;
    }
  }

  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::removeHeadIfPossible(ValueType& item)
  {
    if (size_ == 0) return false;

    removeHead(item);
    return true;
  }

  template <class T, class EnqPolicy>
  void
  ConcurrentQueue<T,EnqPolicy>::removeHead(ValueType& item)
  {
    SequenceType holder;
    // Move the item out of elements_ in a manner that will not throw.
    holder.splice(holder.begin(), elements_, elements_.begin());
    // Record the change in the length of elements_.
    --size_;
    queueNotFull_.notify_one();

    assignItem(item, holder.front());
    used_ -= detail::memoryUsage( item );
  }
  
  template <class T, class EnqPolicy>
  void
  ConcurrentQueue<T,EnqPolicy>::assignItem(T& item, const T& element)
  {
    item = element;
  }
  
  template <class T, class EnqPolicy>
  void
  ConcurrentQueue<T,EnqPolicy>::assignItem(std::pair<T,size_t>& item, const T& element)
  {
    item.first = element;
    item.second = elementsDropped_;
    elementsDropped_ = 0;
  }
  
  template <class T, class EnqPolicy>
  bool
  ConcurrentQueue<T,EnqPolicy>::isFull() const
  {
    if (size_ >= capacity_ || used_ >= memory_) return true;
    return false;
  }

} // namespace stor

#endif // EventFilter_StorageManager_ConcurrentQueue_h