AlignedAllocator.h

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* libscopehal                                                                                                          *
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#ifndef AlignedAllocator_h
#define AlignedAllocator_h
 
#ifdef _WIN32
#include <windows.h>
#endif
 
template <class T, size_t alignment>
class AlignedAllocator
{
public:
 
    typedef T* pointer;
 
    typedef const T* const_pointer;
 
    typedef T& reference;
 
    typedef const T& const_reference;
 
    typedef T value_type;
 
    typedef size_t size_type;
 
    typedef ptrdiff_t difference_type;
 
    T* address(T& rhs)
    { return &rhs; }
 
    const T* address(T& rhs) const
    { return &rhs; }
 
    size_t max_size() const
    { return (static_cast<size_t>(0) - static_cast<size_t>(1)) / sizeof(T); }
 
    template<typename U>
    struct rebind
    {
        typedef AlignedAllocator<U, alignment> other;
    };
 
    bool operator!=(const AlignedAllocator& other) const
    { return !(*this == other); }
 
    //Look at that, a placement new! First time I've ever used one.
    void construct(T* const p, const T& t) const
    { new( static_cast<void*>(p) ) T(t); }
 
    void destroy(T* const p) const
    { p->~T(); }
 
    //Check if this allocator is functionally equivalent to another
    //We have no member variables, so all objects of the same type are equivalent
    bool operator== (const AlignedAllocator& /* unused */) const
    { return true; }
 
    //Default ctors, do nothing
    AlignedAllocator()
    {}
 
    AlignedAllocator(const AlignedAllocator& /* unused */)
    {}
 
    template<typename U>
    AlignedAllocator(const AlignedAllocator<U, alignment>&)
    {}
 
    ~AlignedAllocator()
    {}
 
    T* allocate(size_t n) const
    {
        //Fail if we got an invalid size
        if(n == 0)
            return NULL;
        if(n > max_size())
            throw std::length_error("AlignedAllocator<T>::allocate(): requested size is too large, integer overflow?");
 
        //Round size up to multiple of alignment
        if( (n % alignment) != 0)
        {
            n |= (alignment - 1);
            n ++;
        }
 
        //Do the actual allocation
#ifdef _WIN32
        T* ret = static_cast<T*>(_aligned_malloc(n*sizeof(T), alignment));
#else
        T* ret = static_cast<T*>(aligned_alloc(alignment, n*sizeof(T)));
#endif
 
        //Error check
        if(ret == NULL)
            throw std::bad_alloc();
 
        return ret;
    }
 
    void deallocate(T* const p, [[maybe_unused]] const size_t unused) const
    {
#ifdef _WIN32
        _aligned_free(p);
#else
        free(p);
#endif
    }
 
    void deallocate(T* const p) const
    { deallocate(p, 1); }
 
    //Not quite sure what this is for but apparently we need it?
    template<typename U>
    T* allocate(const size_t n, [[maybe_unused]] const U* const hint)
    { return allocate(n); }
 
    //Disallow assignment
    AlignedAllocator& operator=(const AlignedAllocator&) = delete;
};
 
#endif