Chris@16: #ifndef BOOST_SMART_PTR_DETAIL_QUICK_ALLOCATOR_HPP_INCLUDED
Chris@16: #define BOOST_SMART_PTR_DETAIL_QUICK_ALLOCATOR_HPP_INCLUDED
Chris@16: 
Chris@16: // MS compatible compilers support #pragma once
Chris@16: 
Chris@16: #if defined(_MSC_VER) && (_MSC_VER >= 1020)
Chris@16: # pragma once
Chris@16: #endif
Chris@16: 
Chris@16: //
Chris@16: //  detail/quick_allocator.hpp
Chris@16: //
Chris@16: //  Copyright (c) 2003 David Abrahams
Chris@16: //  Copyright (c) 2003 Peter Dimov
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See
Chris@16: // accompanying file LICENSE_1_0.txt or copy at
Chris@16: // http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: 
Chris@16: #include <boost/config.hpp>
Chris@16: 
Chris@16: #include <boost/smart_ptr/detail/lightweight_mutex.hpp>
Chris@16: #include <boost/type_traits/type_with_alignment.hpp>
Chris@16: #include <boost/type_traits/alignment_of.hpp>
Chris@16: 
Chris@16: #include <new>              // ::operator new, ::operator delete
Chris@16: #include <cstddef>          // std::size_t
Chris@16: 
Chris@16: namespace boost
Chris@16: {
Chris@16: 
Chris@16: namespace detail
Chris@16: {
Chris@16: 
Chris@16: template<unsigned size, unsigned align_> union freeblock
Chris@16: {
Chris@16:     typedef typename boost::type_with_alignment<align_>::type aligner_type;
Chris@16:     aligner_type aligner;
Chris@16:     char bytes[size];
Chris@16:     freeblock * next;
Chris@16: };
Chris@16: 
Chris@16: template<unsigned size, unsigned align_> struct allocator_impl
Chris@16: {
Chris@16:     typedef freeblock<size, align_> block;
Chris@16: 
Chris@16:     // It may seem odd to use such small pages.
Chris@16:     //
Chris@16:     // However, on a typical Windows implementation that uses
Chris@16:     // the OS allocator, "normal size" pages interact with the
Chris@16:     // "ordinary" operator new, slowing it down dramatically.
Chris@16:     //
Chris@16:     // 512 byte pages are handled by the small object allocator,
Chris@16:     // and don't interfere with ::new.
Chris@16:     //
Chris@16:     // The other alternative is to use much bigger pages (1M.)
Chris@16:     //
Chris@16:     // It is surprisingly easy to hit pathological behavior by
Chris@16:     // varying the page size. g++ 2.96 on Red Hat Linux 7.2,
Chris@16:     // for example, passionately dislikes 496. 512 seems OK.
Chris@16: 
Chris@16: #if defined(BOOST_QA_PAGE_SIZE)
Chris@16: 
Chris@16:     enum { items_per_page = BOOST_QA_PAGE_SIZE / size };
Chris@16: 
Chris@16: #else
Chris@16: 
Chris@16:     enum { items_per_page = 512 / size }; // 1048560 / size
Chris@16: 
Chris@16: #endif
Chris@16: 
Chris@16: #ifdef BOOST_HAS_THREADS
Chris@16: 
Chris@16:     static lightweight_mutex & mutex()
Chris@16:     {
Chris@16:         static freeblock< sizeof( lightweight_mutex ), boost::alignment_of< lightweight_mutex >::value > fbm;
Chris@16:         static lightweight_mutex * pm = new( &fbm ) lightweight_mutex;
Chris@16:         return *pm;
Chris@16:     }
Chris@16: 
Chris@16:     static lightweight_mutex * mutex_init;
Chris@16: 
Chris@16: #endif
Chris@16: 
Chris@16:     static block * free;
Chris@16:     static block * page;
Chris@16:     static unsigned last;
Chris@16: 
Chris@16:     static inline void * alloc()
Chris@16:     {
Chris@16: #ifdef BOOST_HAS_THREADS
Chris@16:         lightweight_mutex::scoped_lock lock( mutex() );
Chris@16: #endif
Chris@16:         if(block * x = free)
Chris@16:         {
Chris@16:             free = x->next;
Chris@16:             return x;
Chris@16:         }
Chris@16:         else
Chris@16:         {
Chris@16:             if(last == items_per_page)
Chris@16:             {
Chris@16:                 // "Listen to me carefully: there is no memory leak"
Chris@16:                 // -- Scott Meyers, Eff C++ 2nd Ed Item 10
Chris@16:                 page = ::new block[items_per_page];
Chris@16:                 last = 0;
Chris@16:             }
Chris@16: 
Chris@16:             return &page[last++];
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     static inline void * alloc(std::size_t n)
Chris@16:     {
Chris@16:         if(n != size) // class-specific new called for a derived object
Chris@16:         {
Chris@16:             return ::operator new(n);
Chris@16:         }
Chris@16:         else
Chris@16:         {
Chris@16: #ifdef BOOST_HAS_THREADS
Chris@16:             lightweight_mutex::scoped_lock lock( mutex() );
Chris@16: #endif
Chris@16:             if(block * x = free)
Chris@16:             {
Chris@16:                 free = x->next;
Chris@16:                 return x;
Chris@16:             }
Chris@16:             else
Chris@16:             {
Chris@16:                 if(last == items_per_page)
Chris@16:                 {
Chris@16:                     page = ::new block[items_per_page];
Chris@16:                     last = 0;
Chris@16:                 }
Chris@16: 
Chris@16:                 return &page[last++];
Chris@16:             }
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     static inline void dealloc(void * pv)
Chris@16:     {
Chris@16:         if(pv != 0) // 18.4.1.1/13
Chris@16:         {
Chris@16: #ifdef BOOST_HAS_THREADS
Chris@16:             lightweight_mutex::scoped_lock lock( mutex() );
Chris@16: #endif
Chris@16:             block * pb = static_cast<block *>(pv);
Chris@16:             pb->next = free;
Chris@16:             free = pb;
Chris@16:         }
Chris@16:     }
Chris@16: 
Chris@16:     static inline void dealloc(void * pv, std::size_t n)
Chris@16:     {
Chris@16:         if(n != size) // class-specific delete called for a derived object
Chris@16:         {
Chris@16:             ::operator delete(pv);
Chris@16:         }
Chris@16:         else if(pv != 0) // 18.4.1.1/13
Chris@16:         {
Chris@16: #ifdef BOOST_HAS_THREADS
Chris@16:             lightweight_mutex::scoped_lock lock( mutex() );
Chris@16: #endif
Chris@16:             block * pb = static_cast<block *>(pv);
Chris@16:             pb->next = free;
Chris@16:             free = pb;
Chris@16:         }
Chris@16:     }
Chris@16: };
Chris@16: 
Chris@16: #ifdef BOOST_HAS_THREADS
Chris@16: 
Chris@16: template<unsigned size, unsigned align_>
Chris@16:   lightweight_mutex * allocator_impl<size, align_>::mutex_init = &allocator_impl<size, align_>::mutex();
Chris@16: 
Chris@16: #endif
Chris@16: 
Chris@16: template<unsigned size, unsigned align_>
Chris@16:   freeblock<size, align_> * allocator_impl<size, align_>::free = 0;
Chris@16: 
Chris@16: template<unsigned size, unsigned align_>
Chris@16:   freeblock<size, align_> * allocator_impl<size, align_>::page = 0;
Chris@16: 
Chris@16: template<unsigned size, unsigned align_>
Chris@16:   unsigned allocator_impl<size, align_>::last = allocator_impl<size, align_>::items_per_page;
Chris@16: 
Chris@16: template<class T>
Chris@16: struct quick_allocator: public allocator_impl< sizeof(T), boost::alignment_of<T>::value >
Chris@16: {
Chris@16: };
Chris@16: 
Chris@16: } // namespace detail
Chris@16: 
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #endif  // #ifndef BOOST_SMART_PTR_DETAIL_QUICK_ALLOCATOR_HPP_INCLUDED