Edit File: pool_allocator.h
// Allocators -*- C++ -*- // Copyright (C) 2001-2018 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/>. /* * Copyright (c) 1996-1997 * Silicon Graphics Computer Systems, Inc. * * Permission to use, copy, modify, distribute and sell this software * and its documentation for any purpose is hereby granted without fee, * provided that the above copyright notice appear in all copies and * that both that copyright notice and this permission notice appear * in supporting documentation. Silicon Graphics makes no * representations about the suitability of this software for any * purpose. It is provided "as is" without express or implied warranty. */ /** @file ext/pool_allocator.h * This file is a GNU extension to the Standard C++ Library. */ #ifndef _POOL_ALLOCATOR_H #define _POOL_ALLOCATOR_H 1 #include <bits/c++config.h> #include <cstdlib> #include <new> #include <bits/functexcept.h> #include <ext/atomicity.h> #include <ext/concurrence.h> #include <bits/move.h> #if __cplusplus >= 201103L #include <type_traits> #endif namespace __gnu_cxx _GLIBCXX_VISIBILITY(default) { _GLIBCXX_BEGIN_NAMESPACE_VERSION using std::size_t; using std::ptrdiff_t; /** * @brief Base class for __pool_alloc. * * Uses various allocators to fulfill underlying requests (and makes as * few requests as possible when in default high-speed pool mode). * * Important implementation properties: * 0. If globally mandated, then allocate objects from new * 1. If the clients request an object of size > _S_max_bytes, the resulting * object will be obtained directly from new * 2. In all other cases, we allocate an object of size exactly * _S_round_up(requested_size). Thus the client has enough size * information that we can return the object to the proper free list * without permanently losing part of the object. */ class __pool_alloc_base { protected: enum { _S_align = 8 }; enum { _S_max_bytes = 128 }; enum { _S_free_list_size = (size_t)_S_max_bytes / (size_t)_S_align }; union _Obj { union _Obj* _M_free_list_link; char _M_client_data[1]; // The client sees this. }; static _Obj* volatile _S_free_list[_S_free_list_size]; // Chunk allocation state. static char* _S_start_free; static char* _S_end_free; static size_t _S_heap_size; size_t _M_round_up(size_t __bytes) { return ((__bytes + (size_t)_S_align - 1) & ~((size_t)_S_align - 1)); } _GLIBCXX_CONST _Obj* volatile* _M_get_free_list(size_t __bytes) throw (); __mutex& _M_get_mutex() throw (); // Returns an object of size __n, and optionally adds to size __n // free list. void* _M_refill(size_t __n); // Allocates a chunk for nobjs of size size. nobjs may be reduced // if it is inconvenient to allocate the requested number. char* _M_allocate_chunk(size_t __n, int& __nobjs); }; /** * @brief Allocator using a memory pool with a single lock. * @ingroup allocators */ template<typename _Tp> class __pool_alloc : private __pool_alloc_base { private: static _Atomic_word _S_force_new; 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; template<typename _Tp1> struct rebind { typedef __pool_alloc<_Tp1> other; }; #if __cplusplus >= 201103L // _GLIBCXX_RESOLVE_LIB_DEFECTS // 2103. propagate_on_container_move_assignment typedef std::true_type propagate_on_container_move_assignment; #endif __pool_alloc() _GLIBCXX_USE_NOEXCEPT { } __pool_alloc(const __pool_alloc&) _GLIBCXX_USE_NOEXCEPT { } template<typename _Tp1> __pool_alloc(const __pool_alloc<_Tp1>&) _GLIBCXX_USE_NOEXCEPT { } ~__pool_alloc() _GLIBCXX_USE_NOEXCEPT { } pointer address(reference __x) const _GLIBCXX_NOEXCEPT { return std::__addressof(__x); } const_pointer address(const_reference __x) const _GLIBCXX_NOEXCEPT { return std::__addressof(__x); } size_type max_size() const _GLIBCXX_USE_NOEXCEPT { return size_t(-1) / sizeof(_Tp); } #if __cplusplus >= 201103L template<typename _Up, typename... _Args> void construct(_Up* __p, _Args&&... __args) { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); } template<typename _Up> void destroy(_Up* __p) { __p->~_Up(); } #else // _GLIBCXX_RESOLVE_LIB_DEFECTS // 402. wrong new expression in [some_] allocator::construct void construct(pointer __p, const _Tp& __val) { ::new((void *)__p) _Tp(__val); } void destroy(pointer __p) { __p->~_Tp(); } #endif pointer allocate(size_type __n, const void* = 0); void deallocate(pointer __p, size_type __n); }; template<typename _Tp> inline bool operator==(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) { return true; } template<typename _Tp> inline bool operator!=(const __pool_alloc<_Tp>&, const __pool_alloc<_Tp>&) { return false; } template<typename _Tp> _Atomic_word __pool_alloc<_Tp>::_S_force_new; template<typename _Tp> _Tp* __pool_alloc<_Tp>::allocate(size_type __n, const void*) { pointer __ret = 0; if (__builtin_expect(__n != 0, true)) { if (__n > this->max_size()) std::__throw_bad_alloc(); const size_t __bytes = __n * sizeof(_Tp); #if __cpp_aligned_new if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) { std::align_val_t __al = std::align_val_t(alignof(_Tp)); return static_cast<_Tp*>(::operator new(__bytes, __al)); } #endif // If there is a race through here, assume answer from getenv // will resolve in same direction. Inspired by techniques // to efficiently support threading found in basic_string.h. if (_S_force_new == 0) { if (std::getenv("GLIBCXX_FORCE_NEW")) __atomic_add_dispatch(&_S_force_new, 1); else __atomic_add_dispatch(&_S_force_new, -1); } if (__bytes > size_t(_S_max_bytes) || _S_force_new > 0) __ret = static_cast<_Tp*>(::operator new(__bytes)); else { _Obj* volatile* __free_list = _M_get_free_list(__bytes); __scoped_lock sentry(_M_get_mutex()); _Obj* __restrict__ __result = *__free_list; if (__builtin_expect(__result == 0, 0)) __ret = static_cast<_Tp*>(_M_refill(_M_round_up(__bytes))); else { *__free_list = __result->_M_free_list_link; __ret = reinterpret_cast<_Tp*>(__result); } if (__ret == 0) std::__throw_bad_alloc(); } } return __ret; } template<typename _Tp> void __pool_alloc<_Tp>::deallocate(pointer __p, size_type __n) { if (__builtin_expect(__n != 0 && __p != 0, true)) { #if __cpp_aligned_new if (alignof(_Tp) > __STDCPP_DEFAULT_NEW_ALIGNMENT__) { ::operator delete(__p, std::align_val_t(alignof(_Tp))); return; } #endif const size_t __bytes = __n * sizeof(_Tp); if (__bytes > static_cast<size_t>(_S_max_bytes) || _S_force_new > 0) ::operator delete(__p); else { _Obj* volatile* __free_list = _M_get_free_list(__bytes); _Obj* __q = reinterpret_cast<_Obj*>(__p); __scoped_lock sentry(_M_get_mutex()); __q ->_M_free_list_link = *__free_list; *__free_list = __q; } } } _GLIBCXX_END_NAMESPACE_VERSION } // namespace #endif
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