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## Class template segment_manager

boost::interprocess::segment_manager

## Synopsis

    // In header: <boost/interprocess/segment_manager.hpp>

    template<typename CharType, typename MemoryAlgorithm,
             template< class IndexConfig > class IndexType>
    class segment_manager :
      public boost::interprocess::segment_manager_base< MemoryAlgorithm >
    {
    public:
      // types
      typedef MemoryAlgorithm                                                                 memory_algorithm;
      typedef segment_manager_base_t::void_pointer                                            void_pointer;
      typedef segment_manager_base_t::size_type                                               size_type;
      typedef segment_manager_base_t::difference_type                                         difference_type;
      typedef CharType                                                                        char_type;
      typedef segment_manager_base< MemoryAlgorithm >                                         segment_manager_base_type;
      typedef segment_manager_base_t::mutex_family                                            mutex_family;
      typedef transform_iterator< typename named_index_t::const_iterator, named_transform >   const_named_iterator;
      typedef transform_iterator< typename unique_index_t::const_iterator, unique_transform > const_unique_iterator;

      // member classes/structs/unions
      template<typename T>
      struct allocator {
        // types
        typedef boost::interprocess::allocator< T, segment_manager > type;
      };
      template<typename T>
      struct deleter {
        // types
        typedef boost::interprocess::deleter< T, segment_manager > type;
      };

      // construct/copy/destruct
      explicit segment_manager(size_type);

      // public member functions
      template<typename T> std::pair< T *, size_type > find(char_ptr_holder_t);
      template<typename T>
        std::pair< T *, size_type > find_no_lock(char_ptr_holder_t);
      template<typename T> construct_proxy< T >::type construct(char_ptr_holder_t);
      template<typename T>
        construct_proxy< T >::type find_or_construct(char_ptr_holder_t);
      template<typename T>
        construct_proxy< T >::type
        construct(char_ptr_holder_t, const std::nothrow_t &);
      template<typename T>
        construct_proxy< T >::type
        find_or_construct(char_ptr_holder_t, const std::nothrow_t &);
      template<typename T>
        construct_iter_proxy< T >::type construct_it(char_ptr_holder_t);
      template<typename T>
        construct_iter_proxy< T >::type find_or_construct_it(char_ptr_holder_t);
      template<typename T>
        construct_iter_proxy< T >::type
        construct_it(char_ptr_holder_t, const std::nothrow_t &);
      template<typename T>
        construct_iter_proxy< T >::type
        find_or_construct_it(char_ptr_holder_t, const std::nothrow_t &);
      template<typename Func> void atomic_func(Func &);
      template<typename Func> bool try_atomic_func(Func &);
      template<typename T> bool destroy(char_ptr_holder_t);
      template<typename T> void destroy_ptr(const T *);
      void reserve_named_objects(size_type);
      void reserve_unique_objects(size_type);
      void shrink_to_fit_indexes();
      size_type get_num_named_objects();
      size_type get_num_unique_objects();
      const_named_iterator named_begin() const;
      const_named_iterator named_end() const;
      const_unique_iterator unique_begin() const;
      const_unique_iterator unique_end() const;
      template<typename T> allocator< T >::type get_allocator();
      template<typename T> deleter< T >::type get_deleter();

      // public static functions
      template<typename T> static const CharType * get_instance_name(const T *);
      template<typename T> static size_type get_instance_length(const T *);
      template<typename T> static instance_type get_instance_type(const T *);
      static size_type get_min_size();

      // public data members
      static const size_type PayloadPerAllocation;
    };

## Description

This object is placed in the beginning of memory segment and implements the allocation (named or anonymous) of portions of the segment. This object contains two indexes that maintain an association between a name and a portion of the segment.

The first index contains the mappings for normal named objects using the char type specified in the template parameter.

The second index contains the association for unique instances. The key will be the const char * returned from type_info.name() function for the unique type to be constructed.

segment_manager<CharType, MemoryAlgorithm, IndexType> inherits publicly from segment_manager_base<MemoryAlgorithm> and inherits from it many public functions related to anonymous object and raw memory allocation. See segment_manager_base reference to know about those functions.

### `segment_manager` public construct/copy/destruct

1.     explicit segment_manager(size_type segment_size);

   Constructor of the segment manager "size" is the size of the memory segment where the segment manager is being constructed. Can throw

### `segment_manager` public member functions

1.     template<typename T> std::pair< T *, size_type > find(char_ptr_holder_t name);

   Tries to find a previous named/unique allocation. Returns the address and the object count. On failure the first member of the returned pair is 0.

2.     template<typename T>
         std::pair< T *, size_type > find_no_lock(char_ptr_holder_t name);

   Tries to find a previous named/unique allocation. Returns the address and the object count. On failure the first member of the returned pair is 0. This search is not mutex-protected! Use it only inside atomic_func() calls, where the internal mutex is guaranteed to be locked.

3.     template<typename T>
         construct_proxy< T >::type construct(char_ptr_holder_t name);

   Returns throwing "construct" proxy object

4.     template<typename T>
         construct_proxy< T >::type find_or_construct(char_ptr_holder_t name);

   Returns throwing "search or construct" proxy object

5.     template<typename T>
         construct_proxy< T >::type
         construct(char_ptr_holder_t name, const std::nothrow_t &);

   Returns no throwing "construct" proxy object

6.     template<typename T>
         construct_proxy< T >::type
         find_or_construct(char_ptr_holder_t name, const std::nothrow_t &);

   Returns no throwing "search or construct" proxy object

7.     template<typename T>
         construct_iter_proxy< T >::type construct_it(char_ptr_holder_t name);

   Returns throwing "construct from iterators" proxy object.

8.     template<typename T>
         construct_iter_proxy< T >::type find_or_construct_it(char_ptr_holder_t name);

   Returns throwing "search or construct from iterators" proxy object

9.     template<typename T>
         construct_iter_proxy< T >::type
         construct_it(char_ptr_holder_t name, const std::nothrow_t &);

   Returns no throwing "construct from iterators" proxy object

10.     template<typename T>
          construct_iter_proxy< T >::type
          find_or_construct_it(char_ptr_holder_t name, const std::nothrow_t &);

    Returns no throwing "search or construct from iterators" proxy object

11.     template<typename Func> void atomic_func(Func & f);

    Calls object function blocking recursive `interprocess_mutex` and guarantees that no new named_alloc or destroy will be executed by any process while executing the object function call

12.     template<typename Func> bool try_atomic_func(Func & f);

    Tries to calls a functor guaranteeing that no new construction, search or destruction will be executed by any process while executing the object function call. If the atomic function can't be immediatelly executed because the internal mutex is already locked, returns false. If the functor throws, this function throws.

13.     template<typename T> bool destroy(char_ptr_holder_t name);

    Destroys a previously created named/unique instance. Returns false if the object was not present.

14.     template<typename T> void destroy_ptr(const T * p);

    Destroys an anonymous, unique or named object using its address

15.     void reserve_named_objects(size_type num);

    Preallocates needed index resources to optimize the creation of "num" named objects in the managed memory segment. Can throw `boost::interprocess::bad_alloc` if there is no enough memory.

16.     void reserve_unique_objects(size_type num);

    Preallocates needed index resources to optimize the creation of "num" unique objects in the managed memory segment. Can throw `boost::interprocess::bad_alloc` if there is no enough memory.

17.     void shrink_to_fit_indexes();

    Calls shrink_to_fit in both named and unique object indexes to try to free unused memory from those indexes.

18.     size_type get_num_named_objects();

    Returns the number of named objects stored in the segment.

19.     size_type get_num_unique_objects();

    Returns the number of unique objects stored in the segment.

20.     const_named_iterator named_begin() const;

    Returns a constant iterator to the beginning of the information about the named allocations performed in this segment manager

21.     const_named_iterator named_end() const;

    Returns a constant iterator to the end of the information about the named allocations performed in this segment manager

22.     const_unique_iterator unique_begin() const;

    Returns a constant iterator to the beginning of the information about the unique allocations performed in this segment manager

23.     const_unique_iterator unique_end() const;

    Returns a constant iterator to the end of the information about the unique allocations performed in this segment manager

24.     template<typename T> allocator< T >::type get_allocator();

    Returns an instance of the default allocator for type T initialized that allocates memory from this segment manager.

25.     template<typename T> deleter< T >::type get_deleter();

    Returns an instance of the default deleter for type T that will delete an object constructed in this segment manager.

### `segment_manager` public static functions

1.     template<typename T> static const CharType * get_instance_name(const T * ptr);

   Returns the name of an object created with construct/find_or_construct functions. Does not throw

2.     template<typename T> static size_type get_instance_length(const T * ptr);

   Returns the length of an object created with construct/find_or_construct functions. Does not throw.

3.     template<typename T> static instance_type get_instance_type(const T * ptr);

   Returns is the the name of an object created with construct/find_or_construct functions. Does not throw

4.     static size_type get_min_size();

   Obtains the minimum size needed by the segment manager

### `segment_manager` public public data members

1.     static const size_type PayloadPerAllocation;

   This constant indicates the payload size associated with each allocation of the memory algorithm