hashSet.h

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// -*- Mode: C++; tab-width: 2; -*-
// vi: set ts=2:
//

#ifndef BALL_DATATYPE_HASHSET_H
#define BALL_DATATYPE_HASHSET_H

#ifndef BALL_COMMON_H
# include <BALL/common.h>
#endif

#ifndef BALL_COMMON_HASH_H
# include <BALL/COMMON/hash.h>
#endif

#ifndef BALL_CONCEPT_FORWARDITERATOR_H
# include <BALL/CONCEPT/forwardIterator.h>
#endif

#ifndef BALL_CONCEPT_VISITOR_H
# include <BALL/CONCEPT/visitor.h>
#endif

#ifndef BALL_DATATYPE_FOREACH_H
# include <BALL/DATATYPE/forEach.h>
#endif

#ifndef BALL_CONCEPT_PREDICATE_H
# include <BALL/CONCEPT/predicate.h>
#endif

#ifndef BALL_CONCEPT_PROCESSOR_H
# include <BALL/CONCEPT/processor.h>
#endif

#include <algorithm>


namespace BALL
{
  template <class Key>
  class HashSet
  {
    public:

    typedef Key ValueType;
      
    typedef Key KeyType;

    typedef Key* PointerType;

    // --- EXTERNAL ITERATORS
    struct Node
    {
      Node*       next;
      ValueType   value;

      Node(const KeyType& my_key, const Node* my_next)
        : next(const_cast<Node*>(my_next)),
          value(const_cast<ValueType&>(my_key))
      {
      }
    };

    typedef Node* IteratorPosition;
  
    class IteratorTraits
    {

      friend class HashSet<Key>;
      public:

      IteratorTraits()
        : bound_(0),
          position_(0),
          bucket_(0)
      {
      }
      
      IteratorTraits(const HashSet& hash_set)
        : bound_(const_cast<HashSet*>(&hash_set)),
          position_(0),
          bucket_(0)
      {
      }
      
      IteratorTraits(const IteratorTraits& traits)
        : bound_(traits.bound_),
          position_(traits.position_),
          bucket_(traits.bucket_)
      {
      }
      
      IteratorTraits& operator = (const IteratorTraits& traits)
      {
        bound_ = traits.bound_;
        position_ = traits.position_;
        bucket_ = traits.bucket_;
    
        return *this;
      }

      HashSet* getContainer()
      {
        return bound_;
      }
      
      const HashSet* getContainer() const
      {
        return bound_;
      }
      
      bool isSingular() const
      {
        return (bound_ == 0);
      }
      
      IteratorPosition& getPosition()
      {
        return position_;
      }

      const IteratorPosition& getPosition() const
      {
        return position_;
      }

      bool operator == (const IteratorTraits& traits) const
      {
        return (position_ == traits.position_);
      }

      bool operator != (const IteratorTraits& traits) const
      {
        return (position_ != traits.position_);
      }
      
      bool isValid() const
      {
        return ((bound_ != 0) && (position_ != 0)
                      && (bucket_ < (Position)bound_->bucket_.size()));
      }

      void invalidate()
      {
        bound_ = 0;
        position_ = 0;
        bucket_ = INVALID_POSITION;
      }
      
      void toBegin()
      {
        for (bucket_ = 0;  bucket_ < (Position)bound_->bucket_.size();  ++bucket_)
        {
          position_ = bound_->bucket_[bucket_];

          if (position_ != 0)
          {
            return;
          }
        }
      }

      bool isBegin() const
      {
        for (Position bucket = 0; bucket < (Position)bound_->bucket_.size();  ++bucket)
        {
          if (bound_->bucket_[bucket_] != 0)
          {
            if (position_ == bound_->bucket_[bucket_])
            {
              return true;
            } 
            else 
            {
              return false;
            }
          }
        }

        return false;
      }

      void toEnd()
      {
        position_ = 0;
      }
      
      bool isEnd() const
      {
        return (position_ == 0);
      }
      
      ValueType& getData()
      {
        return position_->value;
      }

      const ValueType& getData() const
      {
        return position_->value;
      }

      void forward()
      {
        position_ = position_->next;

        if (position_ != 0)
        {
          return;
        }

        for (++bucket_;  bucket_ < (Position)bound_->bucket_.size();  ++bucket_)
        {
          position_ = bound_->bucket_[bucket_];

          if (position_ != 0)
          {
            return;
          }
        }
      } 

      protected:

      HashSet*            bound_;
      IteratorPosition    position_;
      Position            bucket_;
    };
    friend class IteratorTraits;


    enum
    {
      INITIAL_CAPACITY          = 4,
      INITIAL_NUMBER_OF_BUCKETS = 3
    };



    class IllegalKey
      : public Exception::GeneralException
    {
      public:
      IllegalKey(const char* file, int line)
        : Exception::GeneralException(file, line)
      {
      }
    };


      
    typedef ForwardIterator<HashSet<Key>, ValueType, PointerType, IteratorTraits> Iterator;

    typedef ConstForwardIterator <HashSet<Key>, ValueType, PointerType, IteratorTraits> ConstIterator;

    // STL compatibility stuff
    typedef Iterator iterator;
    typedef ConstIterator const_iterator;
    typedef Key         value_type;
    typedef Key         key_type;
    typedef Key*        pointer;
    typedef const Key*  const_pointer;
    typedef Key&        reference;
    typedef const Key&  const_reference;
    typedef Size        size_type;
    typedef Index       difference_type;      


    HashSet(Size initial_capacity = INITIAL_CAPACITY, Size number_of_buckets = INITIAL_NUMBER_OF_BUCKETS);
      
    HashSet(const HashSet& hash_set);

    virtual ~HashSet()
    {
      destroy();
      deleteBuckets_();
    }

    virtual void clear();
  
    void destroy();



    void set(const HashSet& hash_set);

    const HashSet& operator = (const HashSet& rhs);

    void get(HashSet& hash_set) const;

    void swap(HashSet& hash_set);



    Size getBucketSize() const;

    Size getCapacity() const;

    Size getSize() const;
      
    Size size() const;

    Iterator find(const Key& key);
  
    ConstIterator find(const Key& key) const;

    std::pair<Iterator, bool> insert(const ValueType& item);

    Iterator insert(Iterator pos, const ValueType& item);

    Size erase(const KeyType& key);

    void erase(Iterator pos);

    void erase(Iterator f, Iterator l);


    const HashSet& operator &= (const HashSet& rhs);
    
    const HashSet& operator |= (const HashSet& rhs);
    
    HashSet operator & (const HashSet& rhs) const;
    
    HashSet operator | (const HashSet& rhs) const;

    HashSet operator + (const HashSet& rhs) const;

    HashSet operator - (const HashSet& rhs) const;

    const HashSet& operator += (const HashSet& rhs);

    const HashSet& operator -= (const HashSet& rhs);


    virtual void host(Visitor<HashSet<Key> >& visitor);


    bool has(const Key& key) const;

    bool isEmpty() const;

    bool operator == (const HashSet& hash_set) const;

    bool operator != (const HashSet& hash_set) const;


    bool isValid() const;

    virtual void dump(std::ostream& s = std::cout, Size depth = 0) const;


    // --- INTERNAL ITERATORS

    bool apply(UnaryProcessor<ValueType>& processor);



    Iterator begin()
    {
      return Iterator::begin(*this);
    }

    Iterator end()
    {
      return Iterator::end(*this);
    }

    ConstIterator begin() const
    {
      return ConstIterator::begin(*this);
    }

    ConstIterator end() const
    {
      return ConstIterator::end(*this);
    }


    protected:

    virtual Node* newNode_(const ValueType& value, Node* next) const;

    virtual void deleteNode_(Node* node) const;
  
    virtual HashIndex hash(const Key& key) const;

    virtual bool needRehashing_() const;

    virtual void rehash();

    private:

    void deleteBuckets_();

    Position hashBucket_(const Key& key) const;

    void rehash_();

    // --- ATTRIBUTES

    /*_ The number of elements in the hash set
    */
    Size  size_;

    /*_ The capacity - usually the number of buckets
    */
    Size  capacity_;

    /*_ Buckets are stored as a vector of linked lists of Nodes 
    */
    vector<Node*> bucket_;
  };


  template <class Key>
  HashSet<Key>::HashSet(Size initial_capacity, Size number_of_buckets)
    : size_(0),
      capacity_(initial_capacity),
      bucket_(number_of_buckets)
  {
    for (Position bucket = 0; bucket < (Position)bucket_.size(); ++bucket)
    {
      bucket_[bucket] = 0;
    }
  }

  template <class Key>
  HashSet<Key>::HashSet(const HashSet& hash_set)
    : size_(hash_set.size_),
      capacity_(hash_set.capacity_),
      bucket_(hash_set.bucket_.size())
  {
    Node* item = 0;
    
    for (Position bucket = 0; bucket < (Position)bucket_.size(); ++bucket)
    {
      bucket_[bucket] = 0;

      for (item = hash_set.bucket_[bucket]; item != 0; item = item->next)
      {
        bucket_[bucket] = newNode_(item->value, bucket_[bucket]);
      }
    }
  }

  template <class Key>
  void HashSet<Key>::set(const HashSet& hash_set)
  {
    if (&hash_set == this)
    {
      return;
    }

    destroy();
    
    deleteBuckets_();

    size_ = hash_set.size_;
    capacity_ = hash_set.capacity_;
    bucket_.resize(hash_set.bucket_.size());

    Node* item = 0;
    
    for (Position bucket = 0; bucket < (Position)bucket_.size(); ++bucket)
    {
      bucket_[bucket] = 0;

      for (item = hash_set.bucket_[bucket]; item != 0; item = item->next)
      {
        bucket_[bucket] = newNode_(item->value, bucket_[bucket]);
      }
    }
  }

  template <class Key>
  void HashSet<Key>::clear()
  {
    Node* node = 0;
    Node* next_node = 0;
    
    for (Position bucket = 0; bucket < (Position)bucket_.size(); ++bucket)
    {
      for (node = bucket_[bucket]; node != 0; node = next_node)
      {
        next_node = node->next;
        deleteNode_(node);
      }
      
      bucket_[bucket] = 0;
    }

    size_ = 0;
  }

  template <class Key>
  BALL_INLINE 
  void HashSet<Key>::destroy()
  {
    clear();
  }

  template <class Key>
  BALL_INLINE 
  const HashSet<Key>& HashSet<Key>::operator = (const HashSet& hash_set)
  {
    set(hash_set);
    return *this;
  }

  template <class Key>
  BALL_INLINE 
  void HashSet<Key>::get(HashSet& hash_set) const

  {
    hash_set.set(*this);
  }

  template <class Key>
  BALL_INLINE 
  void HashSet<Key>::swap(HashSet& hash_set)
  {
    std::swap(size_, hash_set.size_);
    std::swap(capacity_, hash_set.capacity_);
    std::swap(bucket_, hash_set.bucket_);
  }

  template <class Key>
  BALL_INLINE 
  const HashSet<Key>& HashSet<Key>::operator &= (const HashSet& rhs)
  {
    // Store all elements that are not part of the intersection
    // in a list for subsequent deletion.
    std::list<Key> erase_list;
    for (Iterator it = begin(); it != end(); ++it)
    {
      if (!rhs.has(*it))
      {
        erase_list.push_back(*it);
      }
    }

    // erase all elements not part of the intersection
    typename list<Key>::iterator list_it = erase_list.begin();
    for (; list_it != erase_list.end(); ++list_it)
    {
      erase(*list_it);
    }

    return *this;
  }

  template <class Key>
  BALL_INLINE 
  const HashSet<Key>& HashSet<Key>::operator |= (const HashSet<Key>& rhs)
  {
    // Compute the union of both sets by inserting every element of the
    // rhs set.
    for (ConstIterator it = rhs.begin(); it != rhs.end(); ++it)
    {
      insert(*it);
    }

    return *this;
  }

  template <class Key>
  BALL_INLINE 
  const HashSet<Key>& HashSet<Key>::operator += (const HashSet<Key>& rhs)
  {
    return operator |= (rhs);
  }

  template <class Key>
  BALL_INLINE 
  HashSet<Key> HashSet<Key>::operator & (const HashSet<Key>& rhs) const
  {
    // Create an empty hash set...
    HashSet<Key> tmp;
    ConstIterator it = begin();
    
    // ...and copy all the elements contained in the rhs hash set.
    for (; +it; ++it)
    {
      if (rhs.has(*it))
      {
        tmp.insert(*it);
      }
    }

    return tmp;
  }

  template <class Key>
  BALL_INLINE 
  HashSet<Key> HashSet<Key>::operator - (const HashSet<Key>& rhs) const
  {
    // Create an empty hash set...
    HashSet<Key> tmp;
    ConstIterator it = begin();
    
    // ...and copy all the elements contained in this set and not in the rhs hash set.
    for (; +it; ++it)
    {
      if (!rhs.has(*it))
      {
        tmp.insert(*it);
      }
    }

    return tmp;
  }

  template <class Key>
  BALL_INLINE 
  const HashSet<Key>& HashSet<Key>::operator -= (const HashSet<Key>& hash_set) 
  {
    // avoid memory corruption caused by iterating over freed space when
    // deleting myself
    if (this == &hash_set)
    {
      clear();
    }
    else
    {
      // erase all elements which are contained in this and hash_set 
      typename HashSet<Key>::ConstIterator it = hash_set.begin();
      for (; it != hash_set.end(); ++it)
      {
        if (has(*it))
        {
          erase(*it);
        }
      }
    }
    return *this;
  }

  template <class Key>
  BALL_INLINE 
  HashSet<Key> HashSet<Key>::operator | (const HashSet<Key>& rhs) const
  {
    HashSet<Key> tmp(*this);
    tmp |= rhs;

    return tmp;
  }

  template <class Key>
  BALL_INLINE 
  HashSet<Key> HashSet<Key>::operator + (const HashSet<Key>& rhs) const
  {
    return operator | (rhs);
  }

  template <class Key>
  BALL_INLINE 
  Size HashSet<Key>::getBucketSize() const
  {
    return (Size)bucket_.size();
  }

  template <class Key>
  BALL_INLINE 
  Size HashSet<Key>::getCapacity() const
  {
    return capacity_;
  }

  template <class Key>
  BALL_INLINE 
  Size HashSet<Key>::getSize() const
  {
    return size_;
  }

  template <class Key>
  BALL_INLINE 
  Size HashSet<Key>::size() const
  {
    return size_;
  }

  template <class Key>
  typename HashSet<Key>::Iterator HashSet<Key>::find(const Key& key)
  {
    Iterator it = end();
    Position bucket = hashBucket_(key);
    Node* node_ptr = bucket_[bucket];
    while (node_ptr != 0)
    {
      if (node_ptr->value == key)
      {
        it.getTraits().position_ = node_ptr;
        it.getTraits().bucket_ = bucket;
        break;
      }
      node_ptr = node_ptr->next;
    }

    return it;
  }
    
  template <class Key>
  BALL_INLINE 
  typename HashSet<Key>::ConstIterator HashSet<Key>::find(const Key& key) const
  {
    return (const_cast<HashSet*>(this))->find(key);
  }

  template <class Key>
  std::pair<typename HashSet<Key>::Iterator, bool> HashSet<Key>::insert
    (const ValueType& item)
  {
    Iterator it = find(item);
    if (it == end())
    {
      if (needRehashing_() == true)
      {
        rehash_();
      }
      
      Position bucket = hashBucket_(item);

      Node* next = bucket_[bucket];
      bucket_[bucket] = newNode_(item, next);
      
      ++size_;
      it.getTraits().position_ = bucket_[bucket];
      it.getTraits().bucket_ = bucket;
    }

    return std::pair<Iterator, bool>(it, true);
  }

  template <class Key>
  typename HashSet<Key>::Iterator HashSet<Key>::insert
    (typename HashSet<Key>::Iterator /* pos */, const ValueType& item)
  {
    return insert(item).first;
  }

  template <class Key>
  Size HashSet<Key>::erase(const KeyType& key)
  {
    Position  bucket = hashBucket_(key);
    Node*     previous = 0;
    Node*     node_ptr = bucket_[bucket];
    
    while (node_ptr != 0 && node_ptr->value != key)
    {
      previous = node_ptr;
      node_ptr = node_ptr->next;
    }

    if (node_ptr == 0)
    {
      return false;
    }

    if (node_ptr == bucket_[bucket])
    {
      bucket_[bucket] = node_ptr->next;
    } 
    else 
    {
      previous->next = node_ptr->next;
    }

    deleteNode_(node_ptr);
    --size_;

    return 1;
  }

  template <class Key>
  void HashSet<Key>::erase(Iterator pos)
  {
    if (pos.getTraits().bound_ != this)
    {
      throw Exception::IncompatibleIterators(__FILE__, __LINE__);
    }

    if ((pos == end()) || (size_ == 0))
    {
      return;
    }
        
    if (pos.getTraits().position_ == bucket_[pos.getTraits().bucket_])
    {
      bucket_[pos.getTraits().bucket_] = pos.getTraits().position_->next;
    } 
    else 
    {
      // walk over all nodes in this bucket and identify the predecessor
      // of the node refered to by the iterator pos
      Node* prev = bucket_[pos.getTraits().bucket_];
      for (; (prev != 0) && (prev->next != pos.getTraits().position_); prev = prev->next) {};
      if (prev != 0)
      {
        // remove the node and reconnect the list
        prev->next = pos.getTraits().position_->next;
      }
      else 
      {
        throw Exception::InvalidIterator(__FILE__, __LINE__);
      }
    }

    // delete the node and decrement the set size
    deleteNode_(pos.getTraits().position_);
    --size_;
  }

  template <class Key>
  void HashSet<Key>::erase(Iterator f, Iterator l)
  {
    if (f.getTraits().bound_ != this || l.getTraits().bound_ != this)
    {
      throw Exception::IncompatibleIterators(__FILE__, __LINE__);
    }
    
    if (f == end())
    {
      return;
    }

    Position last_bucket = l.getTraits().bucket_;
    if (l == end())
    {
      last_bucket = (Position)(bucket_.size() - 1);
    }

    if (f.getTraits().bucket_ > last_bucket)
    {
      // empty range - l < f
      return;
    }

    // count the deleted entries to correct the set size
    Size no_deletions = 0;

    Position bucket = f.getTraits().bucket_;
    for (; bucket <= last_bucket; bucket++)
    {
      if (bucket_[bucket] == 0)
      {
        // skip all empty buckets
        continue;
      }


      if ((bucket == f.getTraits().bucket_) && (bucket_[bucket] != f.getTraits().position_))
      {
        // find the predecessor of f
        Node* n = bucket_[bucket];
        Node* next;
        for (; (n->next != f.getTraits().position_) && (n->next != 0); n = n->next) {};
        
        if (bucket == last_bucket)
        {
          // delete everything from f to l in this bucket

          next = n->next;
          n->next = l.getTraits().position_;
          for (n = next; (n != 0) && (n != l.getTraits().position_); n = next)
          {
            next = n->next;
            deleteNode_(n);
            no_deletions++;
          }
        }
        else
        {
          // delete everything from f to the end in this bucket

          if (n != 0)
          {
            // mark the end of the list
            next = n->next;
            n->next = 0;

            // delete all remaining nodes
            for (n = next; n != 0; n = next)
            {
              next = n->next;
              deleteNode_(n);
              no_deletions++;
            }
          }
        }
      } 
      // if the current bucket lies between the first and the last bucket...
      else if (bucket < last_bucket)
      {
        // ...delete the whole bucket
        Node* next;
        for (Node* n = bucket_[bucket]; n != 0; n = next)
        {
          next = n->next;
          deleteNode_(n);
          no_deletions++;
        }
        bucket_[bucket] = 0;
      }
      else if (bucket == last_bucket)
      {
        // we delete everything in this bucket up to the iterator l

        // find the predecessor of l
        Node* n = bucket_[bucket];
        Node* next;
        for (; (n != 0) && (n != l.getTraits().position_); n = next)
        {
          next = n->next;
          deleteNode_(n);
          no_deletions++;
        }

        bucket_[bucket] = l.getTraits().position_;
      }
    }

    // correct the set size
    size_ -= no_deletions;
  }

  template <class Key>
  BALL_INLINE 
  void HashSet<Key>::host(Visitor<HashSet<Key> >& visitor)
  {
    visitor.visit(*this);
  }
    
  template <class Key>
  BALL_INLINE 
  bool HashSet<Key>::has(const Key& key) const  
  {
    return (find(key) != end());
  }

  template <class Key>
  BALL_INLINE 
  bool HashSet<Key>::isEmpty() const
  {
    return (size_ == 0);
  }

  template <class Key>
  bool HashSet<Key>::operator == (const HashSet& hash_set) const
  {
    if (size_ != hash_set.size_)
    {
      return false;
    }

    ConstIterator it1 = begin();
    ConstIterator it2 = hash_set.begin();
    while (it1 != end())
    {
      if (*it1 != *it2)
      {
        return false;
      }
      it1++;
      it2++;
    }
    return true;
  }

  template <class Key>
  BALL_INLINE
  bool HashSet<Key>::operator != (const HashSet& hash_set) const
  {
    return !(*this == hash_set);
  }

  template <class Key>
  bool HashSet<Key>::isValid() const
  {
    Size size = 0;
    Node* node = 0;

    for (Position bucket = 0; bucket < (Position)bucket_.size(); ++bucket)
    {
      for (node = bucket_[bucket]; node != 0; node = node->next)
      {
        ++size;

        if (node->next == 0)
        {
          break;
        }
      }
    }

    return (size_ == size);
  }      

  template <class Key>
  void HashSet<Key>::dump(std::ostream& s, Size depth) const
  {
    BALL_DUMP_STREAM_PREFIX(s);

    BALL_DUMP_DEPTH(s, depth);

    BALL_DUMP_DEPTH(s, depth);
    s << "  size: " << getSize() << std::endl;

    BALL_DUMP_DEPTH(s, depth);
    s << "  # buckets: " << getBucketSize() << std::endl;

    BALL_DUMP_DEPTH(s, depth);
    s << "  capacity: " << getCapacity() << std::endl;

    BALL_DUMP_DEPTH(s, depth);
    s << "  load factor: " << (float)size_ / (float)bucket_.size() << std::endl;

    for (Position bucket = 0; bucket < (Position)bucket_.size(); ++bucket)
    {
      BALL_DUMP_DEPTH(s, depth);
      s << "    bucket " << bucket << ": ";
      for (Node* ptr = bucket_[bucket]; ptr != 0; ptr = ptr->next)
      {
        s << "(" << (void*)ptr << ") ";
      }
      s << "(0)" << std::endl;
    }

    BALL_DUMP_STREAM_SUFFIX(s);
  } 
 
  template <class Key>
  bool HashSet<Key>::apply(UnaryProcessor<ValueType>& processor)
  {
    if (processor.start() == false)
    {
      return false;
    }

    Processor::Result result;

    Iterator it = begin();
    while (it != end())
    {
      result = processor(*it);
      if (result <= Processor::BREAK)
      {
        return (result == Processor::BREAK);
      }
      it++;
    }

    return processor.finish();
  }

  template <class Key>
  BALL_INLINE 
  HashIndex HashSet<Key>::hash(const Key& key) const
  {
    return (HashIndex)Hash(key);
  }

  template <class Key>
  BALL_INLINE 
  void HashSet<Key>::rehash()
  {
    capacity_ = (Size)getNextPrime((Size)bucket_.size() << 1);
  }

  template <class Key>
  void HashSet<Key>::deleteBuckets_()
  {
    Size i = 0;
    Node* node = 0;
    Node* next_node = 0;
    for (i = 0; i < bucket_.size(); i++)
    {
      node = bucket_[i];
      while (node != 0)
      {
        next_node = node->next;
        delete node;
        node = next_node;
      }
      bucket_[i] = 0;
    }
  }

  template <class Key>
  BALL_INLINE 
  typename HashSet<Key>::Node* HashSet<Key>::newNode_
    (const ValueType& value, typename HashSet<Key>::Node* next) const
  {
    return new Node(value, next);
  }

  template <class Key>
  BALL_INLINE 
  void HashSet<Key>::deleteNode_(typename HashSet<Key>::Node* node) const
  {
    delete node;
  }

  template <class Key>
  BALL_INLINE 
  bool HashSet<Key>::needRehashing_() const
  {
    return (size_ >= capacity_);
  }

  template <class Key>
  BALL_INLINE 
  HashIndex HashSet<Key>::hashBucket_(const Key& key) const
  {
    return (Position)((HashIndex)hash(key) % (HashIndex)bucket_.size());
  }

  template <class Key>
  void HashSet<Key>::rehash_()
  {
    // calculate the new number of buckets (in capacity_)
    rehash();

    // save the old contents
    vector<Node*> old_buckets(bucket_);

    // resize the bucket vector and initialize it with zero
    bucket_.clear();
    bucket_.resize(capacity_);
    Position i;
    for (i = 0; i < capacity_; i++)
    {
      bucket_[i] = 0;
    }

    // rehash the old contents into the new buckets
    Node* node;
    Node* next_node;
    for (Position i = 0; i < (Position)old_buckets.size(); ++i)
    {
      for (node = old_buckets[i]; node != 0; node = next_node)
      {
        next_node = node->next;
        Position new_bucket = hashBucket_(node->value);
        node->next = bucket_[new_bucket];
        bucket_[new_bucket] = node;
      }
    }
  }
} // namespace BALL

#endif // BALL_DATATYPE_HASHSET_H

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