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// MT-optimized allocator -*- C++ -*-

// Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010

// Free Software Foundation, Inc.

//

// This file is part of the GNU ISO C++ Library.  This library is free

// software; you can redistribute it and/or modify it under the

// terms of the GNU General Public License as published by the

// Free Software Foundation; either version 3, or (at your option)

// any later version.

// This library is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// Under Section 7 of GPL version 3, you are granted additional

// permissions described in the GCC Runtime Library Exception, version

// 3.1, as published by the Free Software Foundation.

// You should have received a copy of the GNU General Public License and

// a copy of the GCC Runtime Library Exception along with this program;

// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see

// <http://www.gnu.org/licenses/>.

/** @file ext/mt_allocator.h

 *  This file is a GNU extension to the Standard C++ Library.

 */

#ifndef _MT_ALLOCATOR_H

#define _MT_ALLOCATOR_H 1

#include <new>

#include <cstdlib>

#include <bits/functexcept.h>

#include <ext/atomicity.h>

#include <bits/move.h>

_GLIBCXX_BEGIN_NAMESPACE(__gnu_cxx)

  using std::size_t;

  using std::ptrdiff_t;

  typedef void (*__destroy_handler)(void*);

  /// Base class for pool object.

  struct __pool_base

  {

    // Using short int as type for the binmap implies we are never

    // caching blocks larger than 32768 with this allocator.

    typedef unsigned short int _Binmap_type;

    // Variables used to configure the behavior of the allocator,

    // assigned and explained in detail below.

    struct _Tune

     {

      // Compile time constants for the default _Tune values.

      enum { _S_align = 8 };

      enum { _S_max_bytes = 128 };

      enum { _S_min_bin = 8 };

      enum { _S_chunk_size = 4096 - 4 * sizeof(void*) };

      enum { _S_max_threads = 4096 };

      enum { _S_freelist_headroom = 10 };

      // Alignment needed.

      // NB: In any case must be >= sizeof(_Block_record), that

      // is 4 on 32 bit machines and 8 on 64 bit machines.

      size_t    _M_align;

      // Allocation requests (after round-up to power of 2) below

      // this value will be handled by the allocator. A raw new/

      // call will be used for requests larger than this value.

      // NB: Must be much smaller than _M_chunk_size and in any

      // case <= 32768.

      size_t    _M_max_bytes;

      // Size in bytes of the smallest bin.

      // NB: Must be a power of 2 and >= _M_align (and of course

      // much smaller than _M_max_bytes).

      size_t    _M_min_bin;

      // In order to avoid fragmenting and minimize the number of

      // new() calls we always request new memory using this

      // value. Based on previous discussions on the libstdc++

      // mailing list we have chosen the value below.

      // See http://gcc.gnu.org/ml/libstdc++/2001-07/msg00077.html

      // NB: At least one order of magnitude > _M_max_bytes. 

      size_t    _M_chunk_size;

      // The maximum number of supported threads. For

      // single-threaded operation, use one. Maximum values will

      // vary depending on details of the underlying system. (For

      // instance, Linux 2.4.18 reports 4070 in

      // /proc/sys/kernel/threads-max, while Linux 2.6.6 reports

      // 65534)

      size_t    _M_max_threads;

      // Each time a deallocation occurs in a threaded application

      // we make sure that there are no more than

      // _M_freelist_headroom % of used memory on the freelist. If

      // the number of additional records is more than

      // _M_freelist_headroom % of the freelist, we move these

      // records back to the global pool.

      size_t    _M_freelist_headroom;

      // Set to true forces all allocations to use new().

      bool      _M_force_new;

      explicit

      _Tune()

      : _M_align(_S_align), _M_max_bytes(_S_max_bytes), _M_min_bin(_S_min_bin),

      _M_chunk_size(_S_chunk_size), _M_max_threads(_S_max_threads),

      _M_freelist_headroom(_S_freelist_headroom),

      _M_force_new(std::getenv("GLIBCXX_FORCE_NEW") ? true : false)

      { }

      explicit

      _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk,

            size_t __maxthreads, size_t __headroom, bool __force)

      : _M_align(__align), _M_max_bytes(__maxb), _M_min_bin(__minbin),

      _M_chunk_size(__chunk), _M_max_threads(__maxthreads),

      _M_freelist_headroom(__headroom), _M_force_new(__force)

      { }

    };

    struct _Block_address

    {

      void*                     _M_initial;

      _Block_address*           _M_next;

    };

    const _Tune&

    _M_get_options() const

    { return _M_options; }

    void

    _M_set_options(_Tune __t)

    {

      if (!_M_init)

        _M_options = __t;

    }

    bool

    _M_check_threshold(size_t __bytes)

    { return __bytes > _M_options._M_max_bytes || _M_options._M_force_new; }

    size_t

    _M_get_binmap(size_t __bytes)

    { return _M_binmap[__bytes]; }

    size_t

    _M_get_align()

    { return _M_options._M_align; }

    explicit

    __pool_base()

    : _M_options(_Tune()), _M_binmap(NULL), _M_init(false) { }

    explicit

    __pool_base(const _Tune& __options)

    : _M_options(__options), _M_binmap(NULL), _M_init(false) { }

  private:

    explicit

    __pool_base(const __pool_base&);

    __pool_base&

    operator=(const __pool_base&);

  protected:

    // Configuration options.

    _Tune                       _M_options;

    _Binmap_type*               _M_binmap;

    // Configuration of the pool object via _M_options can happen

    // after construction but before initialization. After

    // initialization is complete, this variable is set to true.

    bool                        _M_init;

  };

  /**

   *  @brief  Data describing the underlying memory pool, parameterized on

   *  threading support.

   */

  template<bool _Thread>

    class __pool;

  /// Specialization for single thread.

  template<>

    class __pool<false> : public __pool_base

    {

    public:

      union _Block_record

      {

        // Points to the block_record of the next free block.

        _Block_record*                  _M_next;

      };

      struct _Bin_record

      {

        // An "array" of pointers to the first free block.

        _Block_record**                 _M_first;

        // A list of the initial addresses of all allocated blocks.

        _Block_address*                 _M_address;

      };

      void

      _M_initialize_once()

      {

        if (__builtin_expect(_M_init == false, false))

          _M_initialize();

      }

      void

      _M_destroy() throw();

      char*

      _M_reserve_block(size_t __bytes, const size_t __thread_id);

      void

      _M_reclaim_block(char* __p, size_t __bytes) throw ();

      size_t

      _M_get_thread_id() { return 0; }

      const _Bin_record&

      _M_get_bin(size_t __which)

      { return _M_bin[__which]; }

      void

      _M_adjust_freelist(const _Bin_record&, _Block_record*, size_t)

      { }

      explicit __pool()

      : _M_bin(NULL), _M_bin_size(1) { }

      explicit __pool(const __pool_base::_Tune& __tune)

      : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1) { }

    private:

      // An "array" of bin_records each of which represents a specific

      // power of 2 size. Memory to this "array" is allocated in

      // _M_initialize().

      _Bin_record*               _M_bin;

      // Actual value calculated in _M_initialize().

      size_t                    _M_bin_size;

      void

      _M_initialize();

  };

#ifdef __GTHREADS

  /// Specialization for thread enabled, via gthreads.h.

  template<>

    class __pool<true> : public __pool_base

    {

    public:

      // Each requesting thread is assigned an id ranging from 1 to

      // _S_max_threads. Thread id 0 is used as a global memory pool.

      // In order to get constant performance on the thread assignment

      // routine, we keep a list of free ids. When a thread first

      // requests memory we remove the first record in this list and

      // stores the address in a __gthread_key. When initializing the

      // __gthread_key we specify a destructor. When this destructor

      // (i.e. the thread dies) is called, we return the thread id to

      // the front of this list.

      struct _Thread_record

      {

        // Points to next free thread id record. NULL if last record in list.

        _Thread_record*                 _M_next;

        // Thread id ranging from 1 to _S_max_threads.

        size_t                          _M_id;

      };

      union _Block_record

      {

        // Points to the block_record of the next free block.

        _Block_record*                  _M_next;

        // The thread id of the thread which has requested this block.

        size_t                          _M_thread_id;

      };

      struct _Bin_record

      {

        // An "array" of pointers to the first free block for each

        // thread id. Memory to this "array" is allocated in

        // _S_initialize() for _S_max_threads + global pool 0.

        _Block_record**                 _M_first;

        // A list of the initial addresses of all allocated blocks.

        _Block_address*                 _M_address;

        // An "array" of counters used to keep track of the amount of

        // blocks that are on the freelist/used for each thread id.

        // - Note that the second part of the allocated _M_used "array"

        //   actually hosts (atomic) counters of reclaimed blocks:  in

        //   _M_reserve_block and in _M_reclaim_block those numbers are

        //   subtracted from the first ones to obtain the actual size

        //   of the "working set" of the given thread.

        // - Memory to these "arrays" is allocated in _S_initialize()

        //   for _S_max_threads + global pool 0.

        size_t*                         _M_free;

        size_t*                         _M_used;

        // Each bin has its own mutex which is used to ensure data

        // integrity while changing "ownership" on a block.  The mutex

        // is initialized in _S_initialize().

        __gthread_mutex_t*              _M_mutex;

      };

      // XXX GLIBCXX_ABI Deprecated

      void

      _M_initialize(__destroy_handler);

      void

      _M_initialize_once()

      {

        if (__builtin_expect(_M_init == false, false))

          _M_initialize();

      }

      void

      _M_destroy() throw();

      char*

      _M_reserve_block(size_t __bytes, const size_t __thread_id);

      void

      _M_reclaim_block(char* __p, size_t __bytes) throw ();

      const _Bin_record&

      _M_get_bin(size_t __which)

      { return _M_bin[__which]; }

      void

      _M_adjust_freelist(const _Bin_record& __bin, _Block_record* __block,

                         size_t __thread_id)

      {

        if (__gthread_active_p())

          {

            __block->_M_thread_id = __thread_id;

            --__bin._M_free[__thread_id];

            ++__bin._M_used[__thread_id];

          }

      }

      // XXX GLIBCXX_ABI Deprecated

      _GLIBCXX_CONST void

      _M_destroy_thread_key(void*) throw ();

      size_t

      _M_get_thread_id();

      explicit __pool()

      : _M_bin(NULL), _M_bin_size(1), _M_thread_freelist(NULL)

      { }

      explicit __pool(const __pool_base::_Tune& __tune)

      : __pool_base(__tune), _M_bin(NULL), _M_bin_size(1),

      _M_thread_freelist(NULL)

      { }

    private:

      // An "array" of bin_records each of which represents a specific

      // power of 2 size. Memory to this "array" is allocated in

      // _M_initialize().

      _Bin_record*              _M_bin;

      // Actual value calculated in _M_initialize().

      size_t                    _M_bin_size;

      _Thread_record*           _M_thread_freelist;

      void*                     _M_thread_freelist_initial;

      void

      _M_initialize();

    };

#endif

  template<template <bool> class _PoolTp, bool _Thread>

    struct __common_pool

    {

      typedef _PoolTp<_Thread>          pool_type;

      static pool_type&

      _S_get_pool()

      {

        static pool_type _S_pool;

        return _S_pool;

      }

    };

  template<template <bool> class _PoolTp, bool _Thread>

    struct __common_pool_base;

  template<template <bool> class _PoolTp>

    struct __common_pool_base<_PoolTp, false>

    : public __common_pool<_PoolTp, false>

    {

      using  __common_pool<_PoolTp, false>::_S_get_pool;

      static void

      _S_initialize_once()

      {

        static bool __init;

        if (__builtin_expect(__init == false, false))

          {

            _S_get_pool()._M_initialize_once();

            __init = true;

          }

      }

    };

#ifdef __GTHREADS

  template<template <bool> class _PoolTp>

    struct __common_pool_base<_PoolTp, true>

    : public __common_pool<_PoolTp, true>

    {

      using  __common_pool<_PoolTp, true>::_S_get_pool;

      static void

      _S_initialize()

      { _S_get_pool()._M_initialize_once(); }

      static void

      _S_initialize_once()

      {

        static bool __init;

        if (__builtin_expect(__init == false, false))

          {

            if (__gthread_active_p())

              {

                // On some platforms, __gthread_once_t is an aggregate.

                static __gthread_once_t __once = __GTHREAD_ONCE_INIT;

                __gthread_once(&__once, _S_initialize);

              }

            // Double check initialization. May be necessary on some

            // systems for proper construction when not compiling with

            // thread flags.

            _S_get_pool()._M_initialize_once();

            __init = true;

          }

      }

    };

#endif

  /// Policy for shared __pool objects.

  template<template <bool> class _PoolTp, bool _Thread>

    struct __common_pool_policy : public __common_pool_base<_PoolTp, _Thread>

    {

      template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,

               bool _Thread1 = _Thread>

        struct _M_rebind

        { typedef __common_pool_policy<_PoolTp1, _Thread1> other; };

      using  __common_pool_base<_PoolTp, _Thread>::_S_get_pool;

      using  __common_pool_base<_PoolTp, _Thread>::_S_initialize_once;

  };

  template<typename _Tp, template <bool> class _PoolTp, bool _Thread>

    struct __per_type_pool

    {

      typedef _Tp                       value_type;

      typedef _PoolTp<_Thread>          pool_type;

      static pool_type&

      _S_get_pool()

      {

        // Sane defaults for the _PoolTp.

        typedef typename pool_type::_Block_record _Block_record;

        const static size_t __a = (__alignof__(_Tp) >= sizeof(_Block_record)

                                   ? __alignof__(_Tp) : sizeof(_Block_record));

        typedef typename __pool_base::_Tune _Tune;

        static _Tune _S_tune(__a, sizeof(_Tp) * 64,

                             sizeof(_Tp) * 2 >= __a ? sizeof(_Tp) * 2 : __a,

                             sizeof(_Tp) * size_t(_Tune::_S_chunk_size),

                             _Tune::_S_max_threads,

                             _Tune::_S_freelist_headroom,

                             std::getenv("GLIBCXX_FORCE_NEW") ? true : false);

        static pool_type _S_pool(_S_tune);

        return _S_pool;

      }

    };

  template<typename _Tp, template <bool> class _PoolTp, bool _Thread>

    struct __per_type_pool_base;

  template<typename _Tp, template <bool> class _PoolTp>

    struct __per_type_pool_base<_Tp, _PoolTp, false>

    : public __per_type_pool<_Tp, _PoolTp, false>

    {

      using  __per_type_pool<_Tp, _PoolTp, false>::_S_get_pool;

      static void

      _S_initialize_once()

      {

        static bool __init;

        if (__builtin_expect(__init == false, false))

          {

            _S_get_pool()._M_initialize_once();

            __init = true;

          }

      }

    };

 #ifdef __GTHREADS

 template<typename _Tp, template <bool> class _PoolTp>

    struct __per_type_pool_base<_Tp, _PoolTp, true>

    : public __per_type_pool<_Tp, _PoolTp, true>

    {

      using  __per_type_pool<_Tp, _PoolTp, true>::_S_get_pool;

      static void

      _S_initialize()

      { _S_get_pool()._M_initialize_once(); }

      static void

      _S_initialize_once()

      {

        static bool __init;

        if (__builtin_expect(__init == false, false))

          {

            if (__gthread_active_p())

              {

                // On some platforms, __gthread_once_t is an aggregate.

                static __gthread_once_t __once = __GTHREAD_ONCE_INIT;

                __gthread_once(&__once, _S_initialize);

              }

            // Double check initialization. May be necessary on some

            // systems for proper construction when not compiling with

            // thread flags.

            _S_get_pool()._M_initialize_once();

            __init = true;

          }

      }

    };

#endif

  /// Policy for individual __pool objects.

  template<typename _Tp, template <bool> class _PoolTp, bool _Thread>

    struct __per_type_pool_policy

    : public __per_type_pool_base<_Tp, _PoolTp, _Thread>

    {

      template<typename _Tp1, template <bool> class _PoolTp1 = _PoolTp,

               bool _Thread1 = _Thread>

        struct _M_rebind

        { typedef __per_type_pool_policy<_Tp1, _PoolTp1, _Thread1> other; };

      using  __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_get_pool;

      using  __per_type_pool_base<_Tp, _PoolTp, _Thread>::_S_initialize_once;

  };

  /// Base class for _Tp dependent member functions.

  template<typename _Tp>

    class __mt_alloc_base

    {

    public:

      typedef size_t                    size_type;

      typedef ptrdiff_t                 difference_type;

      typedef _Tp*                      pointer;

      typedef const _Tp*                const_pointer;

      typedef _Tp&                      reference;

      typedef const _Tp&                const_reference;

      typedef _Tp                       value_type;

      pointer

      address(reference __x) const

      { return &__x; }

      const_pointer

      address(const_reference __x) const

      { return &__x; }

      size_type

      max_size() const throw()

      { return size_t(-1) / sizeof(_Tp); }

      // _GLIBCXX_RESOLVE_LIB_DEFECTS

      // 402. wrong new expression in [some_] allocator::construct

      void

      construct(pointer __p, const _Tp& __val)

      { ::new((void *)__p) _Tp(__val); }

#ifdef __GXX_EXPERIMENTAL_CXX0X__

      template<typename... _Args>

        void

        construct(pointer __p, _Args&&... __args)

        { ::new((void *)__p) _Tp(std::forward<_Args>(__args)...); }

#endif

      void

      destroy(pointer __p) { __p->~_Tp(); }

    };

#ifdef __GTHREADS

#define __thread_default true

#else

#define __thread_default false

#endif

  /**

   *  @brief  This is a fixed size (power of 2) allocator which - when

   *  compiled with thread support - will maintain one freelist per

   *  size per thread plus a @a global one. Steps are taken to limit

   *  the per thread freelist sizes (by returning excess back to

   *  the @a global list).

   *  @ingroup allocators

   *

   *  Further details:

   *  http://gcc.gnu.org/onlinedocs/libstdc++/manual/bk01pt12ch32.html

   */

  template<typename _Tp,

           typename _Poolp = __common_pool_policy<__pool, __thread_default> >

    class __mt_alloc : public __mt_alloc_base<_Tp>

    {

    public:

      typedef size_t                            size_type;

      typedef ptrdiff_t                         difference_type;

      typedef _Tp*                              pointer;

      typedef const _Tp*                        const_pointer;

      typedef _Tp&                              reference;

      typedef const _Tp&                        const_reference;

      typedef _Tp                               value_type;

      typedef _Poolp                            __policy_type;

      typedef typename _Poolp::pool_type        __pool_type;

      template<typename _Tp1, typename _Poolp1 = _Poolp>

        struct rebind

        {

          typedef typename _Poolp1::template _M_rebind<_Tp1>::other pol_type;

          typedef __mt_alloc<_Tp1, pol_type> other;

        };

      __mt_alloc() throw() { }

      __mt_alloc(const __mt_alloc&) throw() { }

      template<typename _Tp1, typename _Poolp1>

        __mt_alloc(const __mt_alloc<_Tp1, _Poolp1>&) throw() { }

      ~__mt_alloc() throw() { }

      pointer

      allocate(size_type __n, const void* = 0);

      void

      deallocate(pointer __p, size_type __n);

      const __pool_base::_Tune

      _M_get_options()

      {

        // Return a copy, not a reference, for external consumption.

        return __policy_type::_S_get_pool()._M_get_options();

      }

      void

      _M_set_options(__pool_base::_Tune __t)

      { __policy_type::_S_get_pool()._M_set_options(__t); }

    };

  template<typename _Tp, typename _Poolp>

    typename __mt_alloc<_Tp, _Poolp>::pointer

    __mt_alloc<_Tp, _Poolp>::

    allocate(size_type __n, const void*)

    {

      if (__n > this->max_size())

        std::__throw_bad_alloc();

      __policy_type::_S_initialize_once();

      // Requests larger than _M_max_bytes are handled by operator

      // new/delete directly.

      __pool_type& __pool = __policy_type::_S_get_pool();

      const size_t __bytes = __n * sizeof(_Tp);

      if (__pool._M_check_threshold(__bytes))

        {

          void* __ret = ::operator new(__bytes);

          return static_cast<_Tp*>(__ret);

        }

      // Round up to power of 2 and figure out which bin to use.

      const size_t __which = __pool._M_get_binmap(__bytes);

      const size_t __thread_id = __pool._M_get_thread_id();

      // Find out if we have blocks on our freelist.  If so, go ahead

      // and use them directly without having to lock anything.

      char* __c;

      typedef typename __pool_type::_Bin_record _Bin_record;

      const _Bin_record& __bin = __pool._M_get_bin(__which);

      if (__bin._M_first[__thread_id])

        {

          // Already reserved.

          typedef typename __pool_type::_Block_record _Block_record;

          _Block_record* __block = __bin._M_first[__thread_id];

          __bin._M_first[__thread_id] = __block->_M_next;

          __pool._M_adjust_freelist(__bin, __block, __thread_id);

          __c = reinterpret_cast<char*>(__block) + __pool._M_get_align();

        }

      else

        {

          // Null, reserve.

          __c = __pool._M_reserve_block(__bytes, __thread_id);

        }

      return static_cast<_Tp*>(static_cast<void*>(__c));

    }