Allocator

/*  This file is part of the Vc library. {{{
Copyright © 2014 Matthias Kretz <kretz@kde.org>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the names of contributing organizations nor the
      names of its contributors may be used to endorse or promote products
      derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

}}}*/

#ifndef VC_ALLOCATOR_H_
#define VC_ALLOCATOR_H_

#include <new>
#include <cstddef>
#include <cstdlib>
#include <utility>

#include "global.h"
#include "common/macros.h"

#ifdef Vc_MSVC
#define Vc_DECLARE_ALLOCATOR(Type)                                                   \
namespace std                                                                        \
{                                                                                    \
template <> class allocator<Type> : public ::Vc::Allocator<Type>                     \
{                                                                                    \
public:                                                                              \
    template <typename U> struct rebind {                                            \
        typedef ::std::allocator<U> other;                                           \
    };                                                                               \
    /* MSVC brokenness: the following function is optional - just doesn't compile    \
     * without it */                                                                 \
    const allocator &select_on_container_copy_construction() const { return *this; } \
};                                                                                   \
}
#else
#define Vc_DECLARE_ALLOCATOR(Type)                                                   \
namespace std                                                                        \
{                                                                                    \
template <> class allocator<Type> : public ::Vc::Allocator<Type>                     \
{                                                                                    \
public:                                                                              \
    template <typename U> struct rebind {                                            \
        typedef ::std::allocator<U> other;                                           \
    };                                                                               \
};                                                                                   \
}
#endif

namespace Vc_VERSIONED_NAMESPACE
{
    using std::size_t;
    using std::ptrdiff_t;

    template<typename T> class Allocator
    {
    private:
        enum Constants {
#ifdef Vc_HAVE_STD_MAX_ALIGN_T
            NaturalAlignment = alignof(std::max_align_t),
#elif defined(Vc_HAVE_MAX_ALIGN_T)
            NaturalAlignment = alignof(::max_align_t),
#else
            NaturalAlignment = sizeof(void *) > alignof(long double) ? sizeof(void *) :
                (alignof(long double) > alignof(long long) ? alignof(long double) : alignof(long long)),
#endif
#ifdef Vc_IMPL_MIC
            SimdAlignment = 64,
#elif defined Vc_IMPL_AVX
            SimdAlignment = 32,
#elif defined Vc_IMPL_SSE
            SimdAlignment = 16,
#else
            SimdAlignment = 1,
#endif
            Alignment = alignof(T) > SimdAlignment ? alignof(T) : SimdAlignment,
            /* The number of extra bytes allocated must be large enough to put a pointer right
             * before the adjusted address. This pointer stores the original address, which is
             * required to call ::operator delete in deallocate.
             *
             * The address we get from ::operator new is a multiple of NaturalAlignment:
             *   p = N * NaturalAlignment
             *
             * Since all alignments are powers of two, Alignment is a multiple of NaturalAlignment:
             *   Alignment = k * NaturalAlignment
             *
             * two cases:
             * 1. If p is already aligned to Alignment then allocate will return p + Alignment. In
             *    this case there are Alignment Bytes available to store a pointer.
             * 2. If p is not aligned then p + (k - (N modulo k)) * NaturalAlignment will be
             *    returned. Since NaturalAlignment >= sizeof(void*) the pointer fits.
             */
            ExtraBytes = Alignment > NaturalAlignment ? Alignment : 0,
            AlignmentMask = Alignment - 1
        };
    public:
        typedef size_t    size_type;
        typedef ptrdiff_t difference_type;
        typedef T*        pointer;
        typedef const T*  const_pointer;
        typedef T&        reference;
        typedef const T&  const_reference;
        typedef T         value_type;

        template<typename U> struct rebind { typedef Allocator<U> other; };

        Allocator() throw() { }
        Allocator(const Allocator&) throw() { }
        template<typename U> Allocator(const Allocator<U>&) throw() { }

        pointer address(reference x) const { return &x; }
        const_pointer address(const_reference x) const { return &x; }

        pointer allocate(size_type n, const void* = 0)
        {
            if (n > this->max_size()) {
                throw std::bad_alloc();
            }

            char *p = static_cast<char *>(::operator new(n * sizeof(T) + ExtraBytes));
            if (ExtraBytes > 0) {
                char *const pp = p;
                p += ExtraBytes;
                const char *null = 0;
                p -= ((p - null) & AlignmentMask); // equivalent to p &= ~AlignmentMask;
                reinterpret_cast<char **>(p)[-1] = pp;
            }
            return reinterpret_cast<pointer>(p);
        }

        void deallocate(pointer p, size_type)
        {
            if (ExtraBytes > 0) {
                p = reinterpret_cast<pointer *>(p)[-1];
            }
            ::operator delete(p);
        }

        size_type max_size() const throw() { return size_t(-1) / sizeof(T); }

#ifdef Vc_MSVC
        // MSVC brokenness: the following function is optional - just doesn't compile without it
        const Allocator &select_on_container_copy_construction() const { return *this; }

        // MSVC also requires a function that neither C++98 nor C++11 mention
        // but it doesn't support variadic templates... otherwise the Vc_CXX11 clause would be nice
        void construct(pointer p) { ::new(p) T(); }

        // we still need the C++98 version:
        void construct(pointer p, const T& val) { ::new(p) T(val); }
        void destroy(pointer p) { p->~T(); }
#else
        template<typename U, typename... Args> void construct(U* p, Args&&... args)
        {
            ::new(p) U(std::forward<Args>(args)...);
        }
        template<typename U> void destroy(U* p) { p->~U(); }
#endif
    };

    template<typename T> inline bool operator==(const Allocator<T>&, const Allocator<T>&) { return true;  }
    template<typename T> inline bool operator!=(const Allocator<T>&, const Allocator<T>&) { return false; }

}

#include "vector.h"
namespace std
{
    template<typename T> class allocator<Vc::Vector<T> > : public ::Vc::Allocator<Vc::Vector<T> >
    {
    public:
        template<typename U> struct rebind { typedef ::std::allocator<U> other; };
#ifdef Vc_MSVC
        // MSVC brokenness: the following function is optional - just doesn't compile without it
        const allocator &select_on_container_copy_construction() const { return *this; }
#endif
    };
    template <typename T>
    class allocator<Vc::Mask<T>> : public ::Vc::Allocator<Vc::Mask<T>>
    {
    public:
        template<typename U> struct rebind { typedef ::std::allocator<U> other; };
#ifdef Vc_MSVC
        // MSVC brokenness: the following function is optional - just doesn't compile without it
        const allocator &select_on_container_copy_construction() const { return *this; }
#endif
    };
    template <typename T, std::size_t N, typename V, std::size_t M>
    class allocator<Vc::SimdArray<T, N, V, M>> : public ::Vc::Allocator<Vc::SimdArray<T, N, V, M>>
    {
    public:
        template<typename U> struct rebind { typedef ::std::allocator<U> other; };
#ifdef Vc_MSVC
        // MSVC brokenness: the following function is optional - just doesn't compile without it
        const allocator &select_on_container_copy_construction() const { return *this; }
#endif
    };
    template <typename T, std::size_t N, typename V, std::size_t M>
    class allocator<Vc::SimdMaskArray<T, N, V, M>> : public ::Vc::Allocator<Vc::SimdMaskArray<T, N, V, M>>
    {
    public:
        template<typename U> struct rebind { typedef ::std::allocator<U> other; };
#ifdef Vc_MSVC
        // MSVC brokenness: the following function is optional - just doesn't compile without it
        const allocator &select_on_container_copy_construction() const { return *this; }
#endif
    };
}

#endif // VC_ALLOCATOR_H_

// vim: ft=cpp et sw=4 sts=4