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 //
 // detail/hash_map.hpp
 // ~~~~~~~~~~~~~~~~~~~
 //
 // Copyright (c) 2003-2023 Christopher M. Kohlhoff (chris at kohlhoff dot com)
 //
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 //
 
 #ifndef BOOST_ASIO_DETAIL_HASH_MAP_HPP
 #define BOOST_ASIO_DETAIL_HASH_MAP_HPP
 
 #if defined(_MSC_VER) && (_MSC_VER >= 1200)
 # pragma once
 #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
 
 #include <boost/asio/detail/config.hpp>
 #include <list>
 #include <utility>
 #include <boost/asio/detail/assert.hpp>
 #include <boost/asio/detail/noncopyable.hpp>
 
 #if defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
 # include <boost/asio/detail/socket_types.hpp>
 #endif // defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
 
 #include <boost/asio/detail/push_options.hpp>
 
 namespace boost {
 namespace asio {
 namespace detail {
 
 inline std::size_t calculate_hash_value(int i)
 {
   return static_cast<std::size_t>(i);
 }
 
 inline std::size_t calculate_hash_value(void* p)
 {
   return reinterpret_cast<std::size_t>(p)
     + (reinterpret_cast<std::size_t>(p) >> 3);
 }
 
 #if defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
 inline std::size_t calculate_hash_value(SOCKET s)
 {
   return static_cast<std::size_t>(s);
 }
 #endif // defined(BOOST_ASIO_WINDOWS) || defined(__CYGWIN__)
 
 // Note: assumes K and V are POD types.
 template <typename K, typename V>
 class hash_map
   : private noncopyable
 {
 public:
   // The type of a value in the map.
   typedef std::pair<K, V> value_type;
 
   // The type of a non-const iterator over the hash map.
   typedef typename std::list<value_type>::iterator iterator;
 
   // The type of a const iterator over the hash map.
   typedef typename std::list<value_type>::const_iterator const_iterator;
 
   // Constructor.
   hash_map()
     : size_(0),
       buckets_(0),
       num_buckets_(0)
   {
   }
 
   // Destructor.
   ~hash_map()
   {
     delete[] buckets_;
   }
 
   // Get an iterator for the beginning of the map.
   iterator begin()
   {
     return values_.begin();
   }
 
   // Get an iterator for the beginning of the map.
   const_iterator begin() const
   {
     return values_.begin();
   }
 
   // Get an iterator for the end of the map.
   iterator end()
   {
     return values_.end();
   }
 
   // Get an iterator for the end of the map.
   const_iterator end() const
   {
     return values_.end();
   }
 
   // Check whether the map is empty.
   bool empty() const
   {
     return values_.empty();
   }
 
   // Find an entry in the map.
   iterator find(const K& k)
   {
     if (num_buckets_)
     {
       size_t bucket = calculate_hash_value(k) % num_buckets_;
       iterator it = buckets_[bucket].first;
       if (it == values_.end())
         return values_.end();
       iterator end_it = buckets_[bucket].last;
       ++end_it;
       while (it != end_it)
       {
         if (it->first == k)
           return it;
         ++it;
       }
     }
     return values_.end();
   }
 
   // Find an entry in the map.
   const_iterator find(const K& k) const
   {
     if (num_buckets_)
     {
       size_t bucket = calculate_hash_value(k) % num_buckets_;
       const_iterator it = buckets_[bucket].first;
       if (it == values_.end())
         return it;
       const_iterator end_it = buckets_[bucket].last;
       ++end_it;
       while (it != end_it)
       {
         if (it->first == k)
           return it;
         ++it;
       }
     }
     return values_.end();
   }
 
   // Insert a new entry into the map.
   std::pair<iterator, bool> insert(const value_type& v)
   {
     if (size_ + 1 >= num_buckets_)
       rehash(hash_size(size_ + 1));
     size_t bucket = calculate_hash_value(v.first) % num_buckets_;
     iterator it = buckets_[bucket].first;
     if (it == values_.end())
     {
       buckets_[bucket].first = buckets_[bucket].last =
         values_insert(values_.end(), v);
       ++size_;
       return std::pair<iterator, bool>(buckets_[bucket].last, true);
     }
     iterator end_it = buckets_[bucket].last;
     ++end_it;
     while (it != end_it)
     {
       if (it->first == v.first)
         return std::pair<iterator, bool>(it, false);
       ++it;
     }
     buckets_[bucket].last = values_insert(end_it, v);
     ++size_;
     return std::pair<iterator, bool>(buckets_[bucket].last, true);
   }
 
   // Erase an entry from the map.
   void erase(iterator it)
   {
     BOOST_ASIO_ASSERT(it != values_.end());
     BOOST_ASIO_ASSERT(num_buckets_ != 0);
 
     size_t bucket = calculate_hash_value(it->first) % num_buckets_;
     bool is_first = (it == buckets_[bucket].first);
     bool is_last = (it == buckets_[bucket].last);
     if (is_first && is_last)
       buckets_[bucket].first = buckets_[bucket].last = values_.end();
     else if (is_first)
       ++buckets_[bucket].first;
     else if (is_last)
       --buckets_[bucket].last;
 
     values_erase(it);
     --size_;
   }
 
   // Erase a key from the map.
   void erase(const K& k)
   {
     iterator it = find(k);
     if (it != values_.end())
       erase(it);
   }
 
   // Remove all entries from the map.
   void clear()
   {
     // Clear the values.
     values_.clear();
     size_ = 0;
 
     // Initialise all buckets to empty.
     iterator end_it = values_.end();
     for (size_t i = 0; i < num_buckets_; ++i)
       buckets_[i].first = buckets_[i].last = end_it;
   }
 
 private:
   // Calculate the hash size for the specified number of elements.
   static std::size_t hash_size(std::size_t num_elems)
   {
     static std::size_t sizes[] =
     {
 #if defined(BOOST_ASIO_HASH_MAP_BUCKETS)
       BOOST_ASIO_HASH_MAP_BUCKETS
 #else // BOOST_ASIO_HASH_MAP_BUCKETS
       3, 13, 23, 53, 97, 193, 389, 769, 1543, 3079, 6151, 12289, 24593,
       49157, 98317, 196613, 393241, 786433, 1572869, 3145739, 6291469,
       12582917, 25165843
 #endif // BOOST_ASIO_HASH_MAP_BUCKETS
     };
     const std::size_t nth_size = sizeof(sizes) / sizeof(std::size_t) - 1;
     for (std::size_t i = 0; i < nth_size; ++i)
       if (num_elems < sizes[i])
         return sizes[i];
     return sizes[nth_size];
   }
 
   // Re-initialise the hash from the values already contained in the list.
   void rehash(std::size_t num_buckets)
   {
     if (num_buckets == num_buckets_)
       return;
     BOOST_ASIO_ASSERT(num_buckets != 0);
 
     iterator end_iter = values_.end();
 
     // Update number of buckets and initialise all buckets to empty.
     bucket_type* tmp = new bucket_type[num_buckets];
     delete[] buckets_;
     buckets_ = tmp;
     num_buckets_ = num_buckets;
     for (std::size_t i = 0; i < num_buckets_; ++i)
       buckets_[i].first = buckets_[i].last = end_iter;
 
     // Put all values back into the hash.
     iterator iter = values_.begin();
     while (iter != end_iter)
     {
       std::size_t bucket = calculate_hash_value(iter->first) % num_buckets_;
       if (buckets_[bucket].last == end_iter)
       {
         buckets_[bucket].first = buckets_[bucket].last = iter++;
       }
       else if (++buckets_[bucket].last == iter)
       {
         ++iter;
       }
       else
       {
         values_.splice(buckets_[bucket].last, values_, iter++);
         --buckets_[bucket].last;
       }
     }
   }
 
   // Insert an element into the values list by splicing from the spares list,
   // if a spare is available, and otherwise by inserting a new element.
   iterator values_insert(iterator it, const value_type& v)
   {
     if (spares_.empty())
     {
       return values_.insert(it, v);
     }
     else
     {
       spares_.front() = v;
       values_.splice(it, spares_, spares_.begin());
       return --it;
     }
   }
 
   // Erase an element from the values list by splicing it to the spares list.
   void values_erase(iterator it)
   {
     *it = value_type();
     spares_.splice(spares_.begin(), values_, it);
   }
 
   // The number of elements in the hash.
   std::size_t size_;
 
   // The list of all values in the hash map.
   std::list<value_type> values_;
 
   // The list of spare nodes waiting to be recycled. Assumes that POD types only
   // are stored in the hash map.
   std::list<value_type> spares_;
 
   // The type for a bucket in the hash table.
   struct bucket_type
   {
     iterator first;
     iterator last;
   };
 
   // The buckets in the hash.
   bucket_type* buckets_;
 
   // The number of buckets in the hash.
   std::size_t num_buckets_;
 };
 
 } // namespace detail
 } // namespace asio
 } // namespace boost
 
 #include <boost/asio/detail/pop_options.hpp>
 
 #endif // BOOST_ASIO_DETAIL_HASH_MAP_HPP

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