100 lines
3.1 KiB
C++
100 lines
3.1 KiB
C++
/*******************************************************************************
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* Copyright (c) 2021 Nerian Vision GmbH
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*******************************************************************************/
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#ifndef ALIGNEDALLOCATOR_H
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#define ALIGNEDALLOCATOR_H
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#include <cstdlib>
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#include <memory>
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#include <limits>
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namespace visiontransfer {
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namespace internal {
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/**
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* \brief STL-compatible allocator for memory-aligned allocations
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*
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* This is a helper class that is used internally for allocating memory
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* that can be used with aligned SSE / AVX instructions.
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*/
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template<typename T, int alignment = 32>
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class AlignedAllocator {
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public :
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// Typedefs
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typedef T value_type;
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typedef value_type* pointer;
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typedef const value_type* const_pointer;
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typedef value_type& reference;
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typedef const value_type& 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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// convert an allocator<T> to allocator<U>
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template<typename U>
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struct rebind {
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typedef AlignedAllocator<U> other;
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};
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explicit AlignedAllocator() {}
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~AlignedAllocator() {}
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explicit AlignedAllocator(AlignedAllocator const&) {}
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template<typename U>
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explicit AlignedAllocator(AlignedAllocator<U> const&) {}
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// Address
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inline pointer address(reference r) { return &r; }
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inline const_pointer address(const_reference r) { return &r; }
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// Memory allocation
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pointer allocate(size_type cnt, typename std::allocator<void>::const_pointer = 0) {
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// Allocate memory and align it
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unsigned char* ptr = new unsigned char[sizeof(T) * cnt + (alignment-1) + 1];
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unsigned char* alignedPtr = reinterpret_cast<unsigned char*>((size_t(ptr + 1) + alignment-1) & -alignment);
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// Store offset in allocated memory area
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alignedPtr[-1] = static_cast<unsigned char>(alignedPtr - ptr);
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return reinterpret_cast<pointer>(alignedPtr);
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}
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void deallocate(pointer p, size_type) {
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if(p != nullptr) {
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// Get address of unaligned pointer
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unsigned char* alignedPtr = reinterpret_cast<unsigned char*>(p);
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unsigned char* unalignedPtr = alignedPtr - alignedPtr[-1];
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// Delete it
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::operator delete[](unalignedPtr);
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}
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}
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// Size
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size_type max_size() const {
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return std::numeric_limits<size_type>::max() / sizeof(T);
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}
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// Construction
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void construct(pointer p, const T& t) {
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new(p) T(t);
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}
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// Destruction
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void destroy(pointer p) {
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p->~T();
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}
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};
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}} // namespace
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#endif
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