unordered_set.h

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/******************************************************************************
The MIT License(MIT)
 
Embedded Template Library.
https://github.com/ETLCPP/etl
https://www.etlcpp.com
 
Copyright(c) 2016 John Wellbelove
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files(the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and / or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions :
 
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.IN NO EVENT SHALL THE
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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******************************************************************************/
 
#ifndef ETL_UNORDERED_SET_INCLUDED
#define ETL_UNORDERED_SET_INCLUDED
 
#include "platform.h"
#include "algorithm.h"
#include "iterator.h"
#include "functional.h"
#include "utility.h"
#include "pool.h"
#include "vector.h"
#include "intrusive_forward_list.h"
#include "hash.h"
#include "type_traits.h"
#include "nth_type.h"
#include "parameter_type.h"
#include "nullptr.h"
#include "error_handler.h"
#include "exception.h"
#include "error_handler.h"
#include "debug_count.h"
#include "iterator.h"
#include "placement_new.h"
#include "initializer_list.h"
 
#include "private/comparator_is_transparent.h"
 
#include <stddef.h>
 
//*****************************************************************************
//*****************************************************************************
 
namespace etl
{
  //***************************************************************************
  //***************************************************************************
  class unordered_set_exception : public etl::exception
  {
  public:
 
    unordered_set_exception(string_type reason_, string_type file_name_, numeric_type line_number_)
      : etl::exception(reason_, file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class unordered_set_full : public etl::unordered_set_exception
  {
  public:
 
    unordered_set_full(string_type file_name_, numeric_type line_number_)
      : etl::unordered_set_exception(ETL_ERROR_TEXT("unordered_set:full", ETL_UNORDERED_SET_FILE_ID"A"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  class unordered_set_out_of_range : public etl::unordered_set_exception
  {
  public:
 
    unordered_set_out_of_range(string_type file_name_, numeric_type line_number_)
      : etl::unordered_set_exception(ETL_ERROR_TEXT("unordered_set:range", ETL_UNORDERED_SET_FILE_ID"B"), file_name_, line_number_)
    {}
  };
 
  //***************************************************************************
  //***************************************************************************
  class unordered_set_iterator : public etl::unordered_set_exception
  {
  public:
 
    unordered_set_iterator(string_type file_name_, numeric_type line_number_)
      : etl::unordered_set_exception(ETL_ERROR_TEXT("unordered_set:iterator", ETL_UNORDERED_SET_FILE_ID"C"), file_name_, line_number_)
    {
    }
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename THash = etl::hash<TKey>, typename TKeyEqual = etl::equal_to<TKey> >
  class iunordered_set
  {
  public:
 
    typedef TKey              value_type;
    typedef TKey              key_type;
    typedef THash             hasher;
    typedef TKeyEqual         key_equal;
    typedef value_type&       reference;
    typedef const value_type& const_reference;
#if ETL_USING_CPP11
    typedef value_type&&      rvalue_reference;
#endif
    typedef value_type*       pointer;
    typedef const value_type* const_pointer;
    typedef size_t            size_type;
 
    typedef const TKey& key_parameter_t;
 
    typedef etl::forward_link<0> link_t;
 
    //*********************************************************************
    // The nodes that store the elements.
    struct node_t : public link_t
    {
      node_t(const_reference key_)
        : key(key_)
      {
      }
 
      value_type key;
    };
 
    friend bool operator ==(const node_t& lhs, const node_t& rhs)
    {
      return (lhs.key == rhs.key);
    }
 
    friend bool operator !=(const node_t& lhs, const node_t& rhs)
    {
      return !(lhs == rhs);
    }
 
  protected:
 
    typedef etl::intrusive_forward_list<node_t, link_t> bucket_t;
    typedef etl::ipool pool_t;
 
  public:
 
    // Local iterators iterate over one bucket.
    typedef typename bucket_t::iterator       local_iterator;
    typedef typename bucket_t::const_iterator const_local_iterator;
 
    //*********************************************************************
    class iterator : public etl::iterator<ETL_OR_STD::forward_iterator_tag, TKey>
    {
    public:
 
      typedef typename etl::iterator<ETL_OR_STD::forward_iterator_tag, TKey>::value_type value_type;
      typedef typename iunordered_set::key_type        key_type;
      typedef typename iunordered_set::hasher          hasher;
      typedef typename iunordered_set::key_equal       key_equal;
      typedef typename iunordered_set::reference       reference;
      typedef typename iunordered_set::const_reference const_reference;
      typedef typename iunordered_set::pointer         pointer;
      typedef typename iunordered_set::const_pointer   const_pointer;
      typedef typename iunordered_set::size_type       size_type;
 
      friend class iunordered_set;
      friend class const_iterator;
 
      //*********************************
      iterator()
      {
      }
 
      //*********************************
      iterator(const iterator& other)
        : pbuckets_end(other.pbuckets_end)
        , pbucket(other.pbucket)
        , inode(other.inode)
      {
      }
 
      //*********************************
      iterator& operator ++()
      {
        ++inode;
 
        // The end of this node list?
        if (inode == pbucket->end())
        {
          // Search for the next non-empty bucket.
          ++pbucket;
          while ((pbucket != pbuckets_end) && (pbucket->empty()))
          {
            ++pbucket;
          }
 
          // If not past the end, get the first node in the bucket.
          if (pbucket != pbuckets_end)
          {
            inode = pbucket->begin();
          }
        }
 
        return *this;
      }
 
      //*********************************
      iterator operator ++(int)
      {
        iterator temp(*this);
        operator++();
        return temp;
      }
 
      //*********************************
      iterator& operator =(const iterator& other)
      {
        pbuckets_end = other.pbuckets_end;
        pbucket = other.pbucket;
        inode = other.inode;
        return *this;
      }
 
      //*********************************
      reference operator *() const
      {
        return inode->key;
      }
 
      //*********************************
      pointer operator &() const
      {
        return &(inode->key);
      }
 
      //*********************************
      pointer operator ->() const
      {
        return &(inode->key);
      }
 
      //*********************************
      friend bool operator == (const iterator& lhs, const iterator& rhs)
      {
        return lhs.compare(rhs);
      }
 
      //*********************************
      friend bool operator != (const iterator& lhs, const iterator& rhs)
      {
        return !(lhs == rhs);
      }
 
    private:
 
      //*********************************
      iterator(bucket_t* pbuckets_end_, bucket_t* pbucket_, local_iterator inode_)
        : pbuckets_end(pbuckets_end_)
        , pbucket(pbucket_)
        , inode(inode_)
      {
      }
 
      //*********************************
      bool compare(const iterator& rhs) const
      {
        return rhs.inode == inode;
      }
 
      //*********************************
      bucket_t& get_bucket()
      {
        return *pbucket;
      }
 
      //*********************************
      bucket_t*& get_bucket_list_iterator()
      {
        return pbucket;
      }
 
      //*********************************
      local_iterator get_local_iterator()
      {
        return inode;
      }
 
      bucket_t* pbuckets_end;
      bucket_t* pbucket;
      local_iterator       inode;
    };
 
    //*********************************************************************
    class const_iterator : public etl::iterator<ETL_OR_STD::forward_iterator_tag, const TKey>
    {
    public:
 
      typedef typename etl::iterator<ETL_OR_STD::forward_iterator_tag, const TKey>::value_type value_type;
      typedef typename iunordered_set::key_type        key_type;
      typedef typename iunordered_set::hasher          hasher;
      typedef typename iunordered_set::key_equal       key_equal;
      typedef typename iunordered_set::reference       reference;
      typedef typename iunordered_set::const_reference const_reference;
      typedef typename iunordered_set::pointer         pointer;
      typedef typename iunordered_set::const_pointer   const_pointer;
      typedef typename iunordered_set::size_type       size_type;
 
      friend class iunordered_set;
      friend class iterator;
 
      //*********************************
      const_iterator()
      {
      }
 
      //*********************************
      const_iterator(const typename iunordered_set::iterator& other)
        : pbuckets_end(other.pbuckets_end)
        , pbucket(other.pbucket)
        , inode(other.inode)
      {
      }
 
      //*********************************
      const_iterator(const const_iterator& other)
        : pbuckets_end(other.pbuckets_end)
        , pbucket(other.pbucket)
        , inode(other.inode)
      {
      }
 
      //*********************************
      const_iterator& operator ++()
      {
        ++inode;
 
        // The end of this node list?
        if (inode == pbucket->end())
        {
          // Search for the next non-empty bucket.
 
          ++pbucket;
          while ((pbucket != pbuckets_end) && (pbucket->empty()))
          {
            ++pbucket;
          }
 
          // If not past the end, get the first node in the bucket.
          if (pbucket != pbuckets_end)
          {
            inode = pbucket->begin();
          }
        }
 
        return *this;
      }
 
      //*********************************
      const_iterator operator ++(int)
      {
        const_iterator temp(*this);
        operator++();
        return temp;
      }
 
      //*********************************
      const_iterator& operator =(const const_iterator& other)
      {
        pbuckets_end = other.pbuckets_end;
        pbucket = other.pbucket;
        inode = other.inode;
        return *this;
      }
 
      //*********************************
      const_reference operator *() const
      {
        return inode->key;
      }
 
      //*********************************
      const_pointer operator &() const
      {
        return &(inode->key);
      }
 
      //*********************************
      const_pointer operator ->() const
      {
        return &(inode->key);
      }
 
      //*********************************
      friend bool operator == (const const_iterator& lhs, const const_iterator& rhs)
      {
        return lhs.compare(rhs);
      }
 
      //*********************************
      friend bool operator != (const const_iterator& lhs, const const_iterator& rhs)
      {
        return !(lhs == rhs);
      }
 
    private:
 
      //*********************************
      const_iterator(bucket_t* pbuckets_end_, bucket_t* pbucket_, local_iterator inode_)
        : pbuckets_end(pbuckets_end_)
        , pbucket(pbucket_)
        , inode(inode_)
      {
      }
 
      //*********************************
      bool compare(const const_iterator& rhs) const
      {
        return rhs.inode == inode;
      }
 
      //*********************************
      bucket_t& get_bucket()
      {
        return *pbucket;
      }
 
      //*********************************
      bucket_t*& get_bucket_list_iterator()
      {
        return pbucket;
      }
 
      //*********************************
      local_iterator get_local_iterator()
      {
        return inode;
      }
 
      bucket_t* pbuckets_end;
      bucket_t* pbucket;
      local_iterator inode;
    };
 
    typedef typename etl::iterator_traits<iterator>::difference_type difference_type;
 
    //*********************************************************************
    //*********************************************************************
    iterator begin()
    {
      return iterator(pbuckets + number_of_buckets, first, first->begin());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator begin() const
    {
      return const_iterator(pbuckets + number_of_buckets, first, first->begin());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator cbegin() const
    {
      return const_iterator(pbuckets + number_of_buckets, first, first->begin());
    }
 
    //*********************************************************************
    //*********************************************************************
    local_iterator begin(size_t i)
    {
      return pbuckets[i].begin();
    }
 
    //*********************************************************************
    //*********************************************************************
    const_local_iterator begin(size_t i) const
    {
      return pbuckets[i].cbegin();
    }
 
    //*********************************************************************
    //*********************************************************************
    const_local_iterator cbegin(size_t i) const
    {
      return pbuckets[i].cbegin();
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator end()
    {
      return iterator(pbuckets + number_of_buckets, last, last->end());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator end() const
    {
      return const_iterator(pbuckets + number_of_buckets, last, last->end());
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator cend() const
    {
      return const_iterator(pbuckets + number_of_buckets, last, last->end());
    }
 
    //*********************************************************************
    //*********************************************************************
    local_iterator end(size_t i)
    {
      return pbuckets[i].end();
    }
 
    //*********************************************************************
    //*********************************************************************
    const_local_iterator end(size_t i) const
    {
      return pbuckets[i].cend();
    }
 
    //*********************************************************************
    //*********************************************************************
    const_local_iterator cend(size_t i) const
    {
      return pbuckets[i].cend();
    }
 
    //*********************************************************************
    //*********************************************************************
    size_type get_bucket_index(key_parameter_t key) const
    {
      return key_hash_function(key) % number_of_buckets;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    size_type get_bucket_index(const K& key) const
    {
      return key_hash_function(key) % number_of_buckets;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    size_type bucket_size(key_parameter_t key) const
    {
      size_t index = bucket(key);
 
      return etl::distance(pbuckets[index].begin(), pbuckets[index].end());
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    size_type bucket_size(const K& key) const
    {
      size_t index = bucket(key);
 
      return etl::distance(pbuckets[index].begin(), pbuckets[index].end());
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    size_type max_bucket_count() const
    {
      return number_of_buckets;
    }
 
    //*********************************************************************
    //*********************************************************************
    size_type bucket_count() const
    {
      return number_of_buckets;
    }
 
    //*********************************************************************
    //*********************************************************************
    template <typename TIterator>
    void assign(TIterator first_, TIterator last_)
    {
#if ETL_IS_DEBUG_BUILD
      difference_type d = etl::distance(first_, last_);
      ETL_ASSERT(d >= 0, ETL_ERROR(unordered_set_iterator));
      ETL_ASSERT(size_t(d) <= max_size(), ETL_ERROR(unordered_set_full));
#endif
 
      clear();
 
      while (first_ != last_)
      {
        insert(*first_);
        ++first_;
      }
    }
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<iterator, bool> insert(const_reference key)
    {
      ETL_OR_STD::pair<iterator, bool> result(end(), false);
 
      if (full())
      {
        iterator iter = find(key);
        if (iter == end())
        {
          ETL_ASSERT_FAIL(ETL_ERROR(unordered_set_full));
        }
        else
        { 
          result.first = iter;
          result.second = false;
          return result;
        }
      }
 
      // Get the hash index.
      size_t index = get_bucket_index(key);
 
      // Get the bucket & bucket iterator.
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // The first one in the bucket?
      if (bucket.empty())
      {
        // Get a new node.
        node_t* node = allocate_data_node();
        node->clear();
        ::new (&node->key) value_type(key);
        ETL_INCREMENT_DEBUG_COUNT;
 
        // Just add the pointer to the bucket;
        bucket.insert_after(bucket.before_begin(), *node);
        adjust_first_last_markers_after_insert(&bucket);
 
        result.first = iterator(pbuckets + number_of_buckets, pbucket, pbucket->begin());
        result.second = true;
      }
      else
      {
        // Step though the bucket looking for a place to insert.
        local_iterator inode_previous = bucket.before_begin();
        local_iterator inode = bucket.begin();
 
        while (inode != bucket.end())
        {
          // Do we already have this key?
          if (key_equal_function(inode->key, key))
          {
            break;
          }
 
          ++inode_previous;
          ++inode;
        }
 
        // Not already there?
        if (inode == bucket.end())
        {
          // Get a new node.
          node_t* node = allocate_data_node();
          node->clear();
          ::new (&node->key) value_type(key);
          ETL_INCREMENT_DEBUG_COUNT;
 
          // Add the node to the end of the bucket;
          bucket.insert_after(inode_previous, *node);
          adjust_first_last_markers_after_insert(&bucket);
          ++inode_previous;
 
          result.first = iterator(pbuckets + number_of_buckets, pbucket, inode_previous);
          result.second = true;
        }
      }
 
      return result;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    ETL_OR_STD::pair<iterator, bool> insert(const K& key)
    {
      ETL_OR_STD::pair<iterator, bool> result(end(), false);
 
      if (full())
      {
        iterator iter = find(key);
        if (iter == end())
        {
          ETL_ASSERT_FAIL(ETL_ERROR(unordered_set_full));
        }
        else
        { 
          result.first = iter;
          result.second = false;
          return result;
        }
      }
 
      // Get the hash index.
      size_t index = get_bucket_index(key);
 
      // Get the bucket & bucket iterator.
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // The first one in the bucket?
      if (bucket.empty())
      {
        // Get a new node.
        node_t* node = allocate_data_node();
        node->clear();
        ::new (&node->key) value_type(key);
        ETL_INCREMENT_DEBUG_COUNT;
 
        // Just add the pointer to the bucket;
        bucket.insert_after(bucket.before_begin(), *node);
        adjust_first_last_markers_after_insert(&bucket);
 
        result.first = iterator(pbuckets + number_of_buckets, pbucket, pbucket->begin());
        result.second = true;
      }
      else
      {
        // Step though the bucket looking for a place to insert.
        local_iterator inode_previous = bucket.before_begin();
        local_iterator inode = bucket.begin();
 
        while (inode != bucket.end())
        {
          // Do we already have this key?
          if (key_equal_function(inode->key, key))
          {
            break;
          }
 
          ++inode_previous;
          ++inode;
        }
 
        // Not already there?
        if (inode == bucket.end())
        {
          // Get a new node.
          node_t* node = allocate_data_node();
          node->clear();
          ::new (&node->key) value_type(key);
          ETL_INCREMENT_DEBUG_COUNT;
 
          // Add the node to the end of the bucket;
          bucket.insert_after(inode_previous, *node);
          adjust_first_last_markers_after_insert(&bucket);
          ++inode_previous;
 
          result.first = iterator(pbuckets + number_of_buckets, pbucket, inode_previous);
          result.second = true;
        }
      }
 
      return result;
    }
#endif
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<iterator, bool> insert(rvalue_reference key)
    {
      ETL_OR_STD::pair<iterator, bool> result(end(), false);
 
      if (full())
      {
        iterator iter = find(key);
        if (iter == end())
        {
          ETL_ASSERT_FAIL(ETL_ERROR(unordered_set_full));
        }
        else
        { 
          result.first = iter;
          result.second = false;
          return result;
        }
      }
 
      // Get the hash index.
      size_t index = get_bucket_index(key);
 
      // Get the bucket & bucket iterator.
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // The first one in the bucket?
      if (bucket.empty())
      {
        // Get a new node.
        node_t* node = allocate_data_node();
        node->clear();
        ::new (&node->key) value_type(etl::move(key));
        ETL_INCREMENT_DEBUG_COUNT;
 
          // Just add the pointer to the bucket;
          bucket.insert_after(bucket.before_begin(), *node);
        adjust_first_last_markers_after_insert(&bucket);
 
        result.first = iterator(pbuckets + number_of_buckets, pbucket, pbucket->begin());
        result.second = true;
      }
      else
      {
        // Step though the bucket looking for a place to insert.
        local_iterator inode_previous = bucket.before_begin();
        local_iterator inode = bucket.begin();
 
        while (inode != bucket.end())
        {
          // Do we already have this key?
          if (key_equal_function(inode->key, key))
          {
            break;
          }
 
          ++inode_previous;
          ++inode;
        }
 
        // Not already there?
        if (inode == bucket.end())
        {
          // Get a new node.
          node_t* node = allocate_data_node();
          node->clear();
          ::new (&node->key) value_type(etl::move(key));
          ETL_INCREMENT_DEBUG_COUNT;
 
            // Add the node to the end of the bucket;
            bucket.insert_after(inode_previous, *node);
          adjust_first_last_markers_after_insert(&bucket);
          ++inode_previous;
 
          result.first = iterator(pbuckets + number_of_buckets, pbucket, inode_previous);
          result.second = true;
        }
      }
 
      return result;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    iterator insert(const_iterator, const_reference key)
    {
      return insert(key).first;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    iterator insert(const_iterator, rvalue_reference key)
    {
      return insert(etl::move(key)).first;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    template <class TIterator>
    void insert(TIterator first_, TIterator last_)
    {
      while (first_ != last_)
      {
        insert(*first_);
        ++first_;
      }
    }
 
    //*********************************************************************
    //*********************************************************************
    size_t erase(key_parameter_t key)
    {
      size_t n = 0UL;
      size_t index = get_bucket_index(key);
 
      bucket_t& bucket = pbuckets[index];
 
      local_iterator iprevious = bucket.before_begin();
      local_iterator icurrent = bucket.begin();
 
      // Search for the key, if we have it.
      while ((icurrent != bucket.end()) && (!key_equal_function(icurrent->key, key)))
      {
        ++iprevious;
        ++icurrent;
      }
 
      // Did we find it?
      if (icurrent != bucket.end())
      {
        delete_data_node(iprevious, icurrent, bucket);
        n = 1;
      }
 
      return n;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    size_t erase(const K& key)
    {
      size_t n = 0UL;
      size_t index = get_bucket_index(key);
 
      bucket_t& bucket = pbuckets[index];
 
      local_iterator iprevious = bucket.before_begin();
      local_iterator icurrent = bucket.begin();
 
      // Search for the key, if we have it.
      while ((icurrent != bucket.end()) && (!key_equal_function(icurrent->key, key)))
      {
        ++iprevious;
        ++icurrent;
      }
 
      // Did we find it?
      if (icurrent != bucket.end())
      {
        delete_data_node(iprevious, icurrent, bucket);
        n = 1;
      }
 
      return n;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    iterator erase(const_iterator ielement)
    {
      // Make a note of the next one.
      iterator inext((pbuckets + number_of_buckets), ielement.get_bucket_list_iterator(), ielement.get_local_iterator());
      ++inext;
 
      bucket_t&      bucket = ielement.get_bucket();
      local_iterator iprevious = bucket.before_begin();
      local_iterator icurrent = ielement.get_local_iterator();
 
      // Find the node previous to the one we're interested in.
      while (iprevious->etl_next != &*icurrent)
      {
        ++iprevious;
      }
 
      delete_data_node(iprevious, icurrent, bucket);
 
      return inext;
    }
 
    //*********************************************************************
    //*********************************************************************
    iterator erase(const_iterator first_, const_iterator last_)
    {
      // Erasing everything?
      if ((first_ == begin()) && (last_ == end()))
      {
        clear();
        return end();
      }
 
      // Get the starting point.
      bucket_t*      pbucket     = first_.get_bucket_list_iterator();
      bucket_t*      pend_bucket = last_.get_bucket_list_iterator();
      local_iterator iprevious   = pbucket->before_begin();
      local_iterator icurrent    = first_.get_local_iterator();
      local_iterator iend        = last_.get_local_iterator(); // Note: May not be in the same bucket as icurrent.
 
      // Find the node previous to the first one.
      while (iprevious->etl_next != &*icurrent)
      {
        ++iprevious;
      }
 
      // Remember the item before the first erased one.
      iterator ibefore_erased = iterator((pbuckets + number_of_buckets), pbucket, iprevious);
 
      // Until we reach the end.
      while ((icurrent != iend) || (pbucket != pend_bucket))
      {
        icurrent = delete_data_node(iprevious, icurrent, *pbucket);
 
        // Have we not reached the end?
        if ((icurrent != iend) || (pbucket != pend_bucket))
        {
          // At the end of this bucket?
          if ((icurrent == pbucket->end()))
          {
            // Find the next non-empty one.
            do
            {
              ++pbucket;
            } while (pbucket->empty());
 
            iprevious = pbucket->before_begin();
            icurrent  = pbucket->begin();
          }
        }
      }
 
      return ++ibefore_erased;
    }
 
    //*************************************************************************
    //*************************************************************************
    void clear()
    {
      initialise();
    }
 
    //*********************************************************************
    //*********************************************************************
    size_t count(key_parameter_t key) const
    {
      return (find(key) == end()) ? 0 : 1;
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    size_t count(const K& key) const
    {
      return (find(key) == end()) ? 0 : 1;
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    iterator find(key_parameter_t key)
    {
      size_t index = get_bucket_index(key);
 
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // Is the bucket not empty?
      if (!bucket.empty())
      {
        // Step though the list until we find the end or an equivalent key.
        local_iterator inode = bucket.begin();
        local_iterator iend = bucket.end();
 
        while (inode != iend)
        {
          // Do we have this one?
          if (key_equal_function(key, inode->key))
          {
            return iterator(pbuckets + number_of_buckets, pbucket, inode);
          }
 
          ++inode;
        }
      }
 
      return end();
    }
 
    //*********************************************************************
    //*********************************************************************
    const_iterator find(key_parameter_t key) const
    {
      size_t index = get_bucket_index(key);
 
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // Is the bucket not empty?
      if (!bucket.empty())
      {
        // Step though the list until we find the end or an equivalent key.
        local_iterator inode = bucket.begin();
        local_iterator iend = bucket.end();
 
        while (inode != iend)
        {
          // Do we have this one?
          if (key_equal_function(key, inode->key))
          {
            return iterator(pbuckets + number_of_buckets, pbucket, inode);
          }
 
          ++inode;
        }
      }
 
      return end();
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    iterator find(const K& key)
    {
      size_t index = get_bucket_index(key);
 
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // Is the bucket not empty?
      if (!bucket.empty())
      {
        // Step though the list until we find the end or an equivalent key.
        local_iterator inode = bucket.begin();
        local_iterator iend = bucket.end();
 
        while (inode != iend)
        {
          // Do we have this one?
          if (key_equal_function(key, inode->key))
          {
            return iterator(pbuckets + number_of_buckets, pbucket, inode);
          }
 
          ++inode;
        }
      }
 
      return end();
    }
#endif
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    const_iterator find(const K& key) const
    {
      size_t index = get_bucket_index(key);
 
      bucket_t* pbucket = pbuckets + index;
      bucket_t& bucket = *pbucket;
 
      // Is the bucket not empty?
      if (!bucket.empty())
      {
        // Step though the list until we find the end or an equivalent key.
        local_iterator inode = bucket.begin();
        local_iterator iend = bucket.end();
 
        while (inode != iend)
        {
          // Do we have this one?
          if (key_equal_function(key, inode->key))
          {
            return iterator(pbuckets + number_of_buckets, pbucket, inode);
          }
 
          ++inode;
        }
      }
 
      return end();
    }
#endif
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<iterator, iterator> equal_range(key_parameter_t key)
    {
      iterator f = find(key);
      iterator l = f;
 
      if (l != end())
      {
        ++l;
      }
 
      return ETL_OR_STD::pair<iterator, iterator>(f, l);
    }
 
    //*********************************************************************
    //*********************************************************************
    ETL_OR_STD::pair<const_iterator, const_iterator> equal_range(key_parameter_t key) const
    {
      const_iterator f = find(key);
      const_iterator l = f;
 
      if (l != end())
      {
        ++l;
      }
 
      return ETL_OR_STD::pair<const_iterator, const_iterator>(f, l);
    }
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    ETL_OR_STD::pair<iterator, iterator> equal_range(const K& key)
    {
      iterator f = find(key);
      iterator l = f;
 
      if (l != end())
      {
        ++l;
      }
 
      return ETL_OR_STD::pair<iterator, iterator>(f, l);
    }
#endif
 
#if ETL_USING_CPP11
    //*********************************************************************
    //*********************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    ETL_OR_STD::pair<const_iterator, const_iterator> equal_range(const K& key) const
    {
      const_iterator f = find(key);
      const_iterator l = f;
 
      if (l != end())
      {
        ++l;
      }
 
      return ETL_OR_STD::pair<const_iterator, const_iterator>(f, l);
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    size_type size() const
    {
      return pnodepool->size();
    }
 
    //*************************************************************************
    //*************************************************************************
    size_type max_size() const
    {
      return pnodepool->max_size();
    }
 
    //*************************************************************************
    //*************************************************************************
    size_type capacity() const
    {
      return pnodepool->max_size();
    }
 
    //*************************************************************************
    //*************************************************************************
    bool empty() const
    {
      return pnodepool->empty();
    }
 
    //*************************************************************************
    //*************************************************************************
    bool full() const
    {
      return pnodepool->full();
    }
 
    //*************************************************************************
    //*************************************************************************
    size_t available() const
    {
      return pnodepool->available();
    }
 
    //*************************************************************************
    //*************************************************************************
    float load_factor() const
    {
      return static_cast<float>(size()) / static_cast<float>(bucket_count());
    }
 
    //*************************************************************************
    //*************************************************************************
    hasher hash_function() const
    {
      return key_hash_function;
    }
 
    //*************************************************************************
    //*************************************************************************
    key_equal key_eq() const
    {
      return key_equal_function;
    }
 
    //*************************************************************************
    //*************************************************************************
    iunordered_set& operator = (const iunordered_set& rhs)
    {
      // Skip if doing self assignment
      if (this != &rhs)
      {
        key_hash_function  = rhs.hash_function();
        key_equal_function = rhs.key_eq();
        assign(rhs.cbegin(), rhs.cend());
      }
 
      return *this;
    }
 
#if  ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    iunordered_set& operator = (iunordered_set&& rhs)
    {
      // Skip if doing self assignment
      if (this != &rhs)
      {
        clear();
        key_hash_function = rhs.hash_function();
        key_equal_function = rhs.key_eq();
        move(rhs.begin(), rhs.end());
      }
 
      return *this;
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    bool contains(key_parameter_t key) const
    {
      return find(key) != end();
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    template <typename K, typename KE = TKeyEqual, etl::enable_if_t<comparator_is_transparent<KE>::value, int> = 0>
    bool contains(const K& key) const
    {
      return find(key) != end();
    }
#endif
 
  protected:
 
    //*********************************************************************
    //*********************************************************************
    iunordered_set(pool_t& node_pool_, bucket_t* pbuckets_, size_t number_of_buckets_, hasher key_hash_function_, key_equal key_equal_function_)
      : pnodepool(&node_pool_)
      , pbuckets(pbuckets_)
      , number_of_buckets(number_of_buckets_)
      , first(pbuckets)
      , last(pbuckets)
      , key_hash_function(key_hash_function_)
      , key_equal_function(key_equal_function_)
    {
    }
 
    //*********************************************************************
    //*********************************************************************
    void initialise()
    {
      if (!empty())
      {
        // For each bucket...
        for (size_t i = 0UL; i < number_of_buckets; ++i)
        {
          bucket_t& bucket = pbuckets[i];
 
          if (!bucket.empty())
          {
            // For each item in the bucket...
            local_iterator it = bucket.begin();
 
            while (it != bucket.end())
            {
              // Destroy the value contents.
              it->key.~value_type();
              ++it;
              ETL_DECREMENT_DEBUG_COUNT;
            }
 
            // Now it's safe to clear the bucket.
            bucket.clear();
          }
        }
 
        // Now it's safe to clear the entire pool in one go.
        pnodepool->release_all();
      }
 
      first = pbuckets;
      last  = first;
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    void move(iterator b, iterator e)
    {
#if ETL_IS_DEBUG_BUILD
      difference_type d = etl::distance(b, e);
      ETL_ASSERT(d >= 0, ETL_ERROR(unordered_set_iterator));
      ETL_ASSERT(size_t(d) <= max_size(), ETL_ERROR(unordered_set_full));
#endif
 
      while (b != e)
      {
        iterator temp = b;
        ++temp;
        insert(etl::move(*b));
        b = temp;
      }
    }
#endif
 
  private:
 
    //*************************************************************************
    //*************************************************************************
    node_t* allocate_data_node()
    {
      node_t* (etl::ipool::*func)() = &etl::ipool::allocate<node_t>;
      return (pnodepool->*func)();
    }
 
    //*********************************************************************
    //*********************************************************************
    void adjust_first_last_markers_after_insert(bucket_t* pbucket)
    {
      if (size() == 1)
      {
        first = pbucket;
        last  = pbucket;
      }
      else
      {
        if (pbucket < first)
        {
          first = pbucket;
        }
        else if (pbucket > last)
        {
          last = pbucket;
        }
      }
    }
 
    //*********************************************************************
    //*********************************************************************
    void adjust_first_last_markers_after_erase(bucket_t* pbucket)
    {
      if (empty())
      {
        first = pbuckets;
        last = pbuckets;
      }
      else
      {
        if (pbucket == first)
        {
          // We erased the first so, we need to search again from where we erased.
          while (first->empty())
          {
            ++first;
          }
        }
        else if (pbucket == last)
        {
          // We erased the last, so we need to search again. Start from the first, go no further than the current last.
          pbucket = first;
          bucket_t* pend = last;
 
          last = first;
 
          while (pbucket != pend)
          {
            if (!pbucket->empty())
            {
              last = pbucket;
            }
 
            ++pbucket;
          }
        }
      }
    }
 
    //*********************************************************************
    //*********************************************************************
    local_iterator delete_data_node(local_iterator iprevious, local_iterator icurrent, bucket_t& bucket)
    {
      local_iterator inext = bucket.erase_after(iprevious); // Unlink from the bucket.
      icurrent->key.~value_type();                          // Destroy the value.
      pnodepool->release(&*icurrent);                       // Release it back to the pool.
      adjust_first_last_markers_after_erase(&bucket);
      ETL_DECREMENT_DEBUG_COUNT;
 
      return inext;
    }
 
    // Disable copy construction.
    iunordered_set(const iunordered_set&);
 
    pool_t* pnodepool;
 
    bucket_t* pbuckets;
 
    const size_t number_of_buckets;
 
    bucket_t* first;
    bucket_t* last;
 
    hasher key_hash_function;
 
    key_equal key_equal_function;
 
    ETL_DECLARE_DEBUG_COUNT;
 
      //*************************************************************************
      //*************************************************************************
#if defined(ETL_POLYMORPHIC_UNORDERED_SET) || defined(ETL_POLYMORPHIC_CONTAINERS)
  public:
    virtual ~iunordered_set()
    {
    }
#else
  protected:
    ~iunordered_set()
    {
    }
#endif
  };
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename THash, typename TKeyEqual>
  bool operator ==(const etl::iunordered_set<TKey, THash, TKeyEqual>& lhs, 
                   const etl::iunordered_set<TKey, THash, TKeyEqual>& rhs)
  {
    const bool sizes_match = (lhs.size() == rhs.size());
    bool elements_match = true;
 
    typedef typename etl::iunordered_set<TKey, THash, TKeyEqual>::const_iterator itr_t;
 
    if (sizes_match)
    {
      itr_t l_begin = lhs.begin();
      itr_t l_end   = lhs.end();
 
      while ((l_begin != l_end) && elements_match)
      {
        const TKey l_value = *l_begin;
 
        // See if the lhs key exists in the rhs.
        ETL_OR_STD::pair<itr_t, itr_t> range = rhs.equal_range(l_value);
 
        if (range.first != rhs.end())
        {
          // See if the values match
          const TKey r_value = *(range.first);
 
          elements_match = (r_value == l_value);
        }
        else
        {
          elements_match = false;
        }
 
        ++l_begin;
      }
    }
 
    return (sizes_match && elements_match);
  }
 
  //***************************************************************************
  //***************************************************************************
  template <typename TKey, typename THash, typename TKeyEqual>
  bool operator !=(const etl::iunordered_set<TKey, THash, TKeyEqual>& lhs, 
                   const etl::iunordered_set<TKey, THash, TKeyEqual>& rhs)
  {
    return !(lhs == rhs);
  }
 
  //*************************************************************************
  //*************************************************************************
  template <typename TKey, const size_t MAX_SIZE_, size_t MAX_BUCKETS_ = MAX_SIZE_, typename THash = etl::hash<TKey>, typename TKeyEqual = etl::equal_to<TKey> >
  class unordered_set : public etl::iunordered_set<TKey, THash, TKeyEqual>
  {
  private:
 
    typedef etl::iunordered_set<TKey, THash, TKeyEqual> base;
 
  public:
 
    static ETL_CONSTANT size_t MAX_SIZE    = MAX_SIZE_;
    static ETL_CONSTANT size_t MAX_BUCKETS = MAX_BUCKETS_;
 
    //*************************************************************************
    //*************************************************************************
    unordered_set(const THash& hash = THash(), const TKeyEqual& equal = TKeyEqual())
      : base(node_pool, buckets, MAX_BUCKETS, hash, equal)
    {
    }
 
    //*************************************************************************
    //*************************************************************************
    unordered_set(const unordered_set& other)
      : base(node_pool, buckets, MAX_BUCKETS, other.hash_function(), other.key_eq())
    {
      // Skip if doing self assignment
      if (this != &other)
      {
        base::assign(other.cbegin(), other.cend());
      }
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    unordered_set(unordered_set&& other)
      : base(node_pool, buckets, MAX_BUCKETS, other.hash_function(), other.key_eq())
    {
      // Skip if doing self assignment
      if (this != &other)
      {
        base::move(other.begin(), other.end());
      }
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    template <typename TIterator>
    unordered_set(TIterator first_, TIterator last_, const THash& hash = THash(), const TKeyEqual& equal = TKeyEqual())
      : base(node_pool, buckets, MAX_BUCKETS, hash, equal)
    {
      base::assign(first_, last_);
    }
 
#if ETL_HAS_INITIALIZER_LIST
    //*************************************************************************
    //*************************************************************************
    unordered_set(std::initializer_list<TKey> init, const THash& hash = THash(), const TKeyEqual& equal = TKeyEqual())
      : base(node_pool, buckets, MAX_BUCKETS, hash, equal)
    {
      base::assign(init.begin(), init.end());
    }
#endif
 
    //*************************************************************************
    //*************************************************************************
    ~unordered_set()
    {
      base::initialise();
    }
 
    //*************************************************************************
    //*************************************************************************
    unordered_set& operator = (const unordered_set& rhs)
    {
      base::operator=(rhs);
 
      return *this;
    }
 
#if ETL_USING_CPP11
    //*************************************************************************
    //*************************************************************************
    unordered_set& operator = (unordered_set&& rhs)
    {
      base::operator=(etl::move(rhs));
 
      return *this;
    }
#endif
 
  private:
 
    etl::pool<typename base::node_t, MAX_SIZE> node_pool;
 
    typename base::bucket_t buckets[MAX_BUCKETS_];
  };
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_CPP17 && ETL_HAS_INITIALIZER_LIST
  template <typename... T>
  unordered_set(T...) -> unordered_set<etl::nth_type_t<0, T...>, sizeof...(T)>;
#endif
 
  //*************************************************************************
  //*************************************************************************
#if ETL_USING_CPP11 && ETL_HAS_INITIALIZER_LIST
  template <typename TKey, typename THash = etl::hash<TKey>, typename TKeyEqual = etl::equal_to<TKey>, typename... T>
  constexpr auto make_unordered_set(T&&... keys) -> etl::unordered_set<TKey, sizeof...(T), sizeof...(T), THash, TKeyEqual>
  {
    return { etl::forward<T>(keys)... };
  }
#endif
}
 
#endif