debug_size_heap.hpp

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//
// immer: immutable data structures for C++
// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
//
// This software is distributed under the Boost Software License, Version 1.0.
// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
//

#pragma once

#include <cassert>
#include <cstddef>
#include <immer/config.hpp>
#include <immer/heap/identity_heap.hpp>

namespace immer {

#if IMMER_ENABLE_DEBUG_SIZE_HEAP

template <typename Base>
struct debug_size_heap
{
    // temporary fix until https://github.com/arximboldi/immer/issues/78 is fixed
    constexpr static auto extra_size = sizeof(void*) * 2; //alignof(std::max_align_t);

    template <typename... Tags>
    static void* allocate(std::size_t size, Tags... tags)
    {
        auto p = (std::size_t*) Base::allocate(size + extra_size, tags...);
        *p = size;
        return ((char*)p) + extra_size;
    }

    template <typename... Tags>
    static void deallocate(std::size_t size, void* data, Tags... tags)
    {
        auto p = (std::size_t*) (((char*) data) - extra_size);
        assert(*p == size);
        Base::deallocate(size + extra_size, p, tags...);
    }
};

#else // IMMER_ENABLE_DEBUG_SIZE_HEAP

template <typename Base>
using debug_size_heap = identity_heap<Base>;

#endif // !IMMER_ENABLE_DEBUG_SIZE_HEAP

} // namespace immer