143 lines
3.6 KiB
C++
143 lines
3.6 KiB
C++
/* Copyright (C) 2009 Wildfire Games.
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* This file is part of 0 A.D.
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*
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* 0 A.D. is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 2 of the License, or
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* (at your option) any later version.
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*
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* 0 A.D. is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with 0 A.D. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*
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* STL allocator for aligned memory
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*/
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#ifndef ALIGNED_ALLOCATOR
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#define ALIGNED_ALLOCATOR
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#include "lib/bits.h" // round_up
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#include "lib/sysdep/arch/x86_x64/x86_x64.h" // x86_x64_L1CacheLineSize
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#include "lib/sysdep/rtl.h" // rtl_AllocateAligned
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/**
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* stateless STL allocator that aligns elements to the L1 cache line size.
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*
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* note: the alignment is hard-coded to avoid any allocator state.
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* this avoids portability problems, which is important since allocators
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* are rather poorly specified.
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*
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* references:
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* http://www.tantalon.com/pete/customallocators.ppt
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* http://www.flipcode.com/archives/Aligned_Block_Allocation.shtml
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* http://www.josuttis.com/cppcode/allocator.html
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*
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* derived from code that bears the following copyright notice:
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* (C) Copyright Nicolai M. Josuttis 1999.
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* Permission to copy, use, modify, sell and distribute this software
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* is granted provided this copyright notice appears in all copies.
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* This software is provided "as is" without express or implied
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* warranty, and with no claim as to its suitability for any purpose.
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**/
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template<class T>
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class AlignedAllocator
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{
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public:
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// type definitions
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typedef T value_type;
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typedef T* pointer;
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typedef const T* const_pointer;
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typedef T& reference;
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typedef const T& const_reference;
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typedef std::size_t size_type;
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typedef std::ptrdiff_t difference_type;
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// rebind allocator to type U
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template <class U>
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struct rebind
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{
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typedef AlignedAllocator<U> other;
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};
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pointer address(reference value) const
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{
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return &value;
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}
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const_pointer address(const_reference value) const
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{
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return &value;
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}
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AlignedAllocator() throw()
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{
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}
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AlignedAllocator(const AlignedAllocator&) throw()
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{
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}
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template <class U>
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AlignedAllocator (const AlignedAllocator<U>&) throw()
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{
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}
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~AlignedAllocator() throw()
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{
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}
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size_type max_size() const throw()
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{
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// maximum number of *elements* that can be allocated
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return std::numeric_limits<std::size_t>::max() / sizeof(T);
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}
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// allocate uninitialized storage
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pointer allocate(size_type numElements, const void* hint = 0)
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{
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const size_type alignment = x86_x64_L1CacheLineSize();
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const size_type elementSize = round_up(sizeof(T), alignment);
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const size_type size = numElements * elementSize;
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pointer p = (pointer)rtl_AllocateAligned(size, alignment);
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return p;
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}
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// deallocate storage of elements that have been destroyed
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void deallocate(pointer p, size_type num)
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{
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rtl_FreeAligned((void*)p);
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}
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void construct(pointer p, const T& value)
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{
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new((void*)p) T(value);
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}
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void destroy(pointer p)
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{
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p->~T();
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}
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};
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// indicate that all specializations of this allocator are interchangeable
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template <class T1, class T2>
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bool operator==(const AlignedAllocator<T1>&, const AlignedAllocator<T2>&) throw()
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{
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return true;
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}
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template <class T1, class T2>
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bool operator!=(const AlignedAllocator<T1>&, const AlignedAllocator<T2>&) throw()
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{
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return false;
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}
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#endif // #ifndef ALIGNED_ALLOCATOR
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