# Singleton Pool Implementation

## Dependencies

Includes the Boost headers "pool.hpp" (see pool.html), "detail/singleton.hpp" (see singleton.html), "detail/mutex.hpp" (see mutex.html), and "detail/guard.hpp" (see guard.html).

## Synopsis

    template <typename Tag,
        unsigned RequestedSize,
        typename UserAllocator = default_user_allocator_new_delete,
        typename Mutex = details::pool::default_mutex,
        unsigned NextSize = 32>
    class singleton_pool
    {
      ... // public interface

      public: // extensions to public interface
        typedef Mutex mutex;
        static const unsigned next_size = NextSize;
    };

## Extensions to Public Interface

### Additional template parameters

#### Mutex

This class is the type of mutex to use to protect simultaneous access to the underlying Pool. It is exposed so that users may declare some singleton pools normally (i.e., with synchronization), but some singleton pools without synchronization (by specifying details::pool::null_mutex) for efficiency reasons.

#### NextSize

The value of this parameter is passed to the underlying Pool when it is created. See the extensions to the public interface of pool for more information.

### Additional members

The typedef mutex and the static const value next_size publish the values of the template parameters Mutex and NextSize, respectively.

## Future Directions

When the Boost multithreading library is completed, the Mutex parameter will be replaced by something from that library providing the same flexibility and will move from an implementation detail into the interface specification.

## Interface Description

Revised 05 December, 2006

Copyright © 2000, 2001 Stephen Cleary (scleary AT jerviswebb 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)