overflow.h

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#pragma once
 
#include "../utility/assert.h"
#include "../utility/empty_base.h"
#include "../utility/meta.h"
#include "overflow_fwd.h"
#include "type_allocator.h"
 
#include <cstring>
#include <memory>
#include <ostream>
#include <type_traits>
 
namespace ktl
{
    template<typename Alloc, typename Stream>
    class overflow
    {
    private:
        static_assert(detail::has_no_value_type_v<Alloc>, "Building on top of typed allocators is not allowed. Use allocators without a type");
 
    public:
        typedef typename detail::get_size_type_t<Alloc> size_type;
 
    private:
        static constexpr unsigned int OVERFLOW_PATTERN = 0b10100101101001011010010110100101;
        static constexpr unsigned char OVERFLOW_TEST = 0b10100101;
        static constexpr size_t OVERFLOW_SIZE = 64;
 
    public:
        explicit overflow(Stream& stream)
            noexcept(std::is_nothrow_default_constructible_v<Alloc>) :
            m_Stream(stream),
            m_Alloc(),
            m_Allocs(0),
            m_Constructs(0) {}
 
        template<typename... Args,
            typename = std::enable_if_t<
            std::is_constructible_v<Alloc, Args...>>>
        explicit overflow(Stream& stream, Args&&... args)
            noexcept(std::is_nothrow_constructible_v<Alloc, Args...>) :
            m_Stream(stream),
            m_Alloc(std::forward<Args>(args)...),
            m_Allocs(0),
            m_Constructs(0) {}
 
        overflow(const overflow&) = default;
 
        overflow(overflow&&) = default;
 
        ~overflow()
        {
            if (m_Allocs != 0)
            {
                m_Stream << "--------MEMORY LEAK DETECTED--------\nAllocator destroyed while having:\n";
                if (m_Allocs > 0)
                    m_Stream << " Allocated memory (" << m_Allocs << " bytes)\n";
                else
                    m_Stream << " Too many frees (" << -m_Allocs << " bytes)\n";
            }
 
            if (m_Constructs != 0)
            {
                m_Stream << "--------POSSIBLE LOGIC ERROR DETECTED--------\nAllocator destroyed while having:\n";
                if (m_Constructs > 0)
                    m_Stream << " Too many constructor calls (" << m_Constructs << ")\n";
                else
                    m_Stream << " Too many destructor calls (" << -m_Constructs << ")\n";
            }
        }
 
        overflow& operator=(const overflow&) = default;
 
        overflow& operator=(overflow&&) = default;
 
        bool operator==(const overflow& rhs) const
            noexcept(detail::has_nothrow_equal_v<Alloc>)
        {
            return m_Alloc == rhs.m_Alloc;
        }
 
        bool operator!=(const overflow& rhs) const
            noexcept(detail::has_nothrow_not_equal_v<Alloc>)
        {
            return m_Alloc != rhs.m_Alloc;
        }
 
#pragma region Allocation
        void* allocate(size_type n)
            noexcept(detail::has_nothrow_allocate_v<Alloc>)
        {
            m_Allocs += n;
 
            size_type size = n + OVERFLOW_SIZE * 2;
            char* ptr = reinterpret_cast<char*>(m_Alloc.allocate(size));
 
            if (!ptr)
                return nullptr;
 
            std::memset(ptr, OVERFLOW_PATTERN, OVERFLOW_SIZE);
            std::memset(ptr + OVERFLOW_SIZE + n, OVERFLOW_PATTERN, OVERFLOW_SIZE);
 
            return ptr + OVERFLOW_SIZE;
        }
 
        void deallocate(void* p, size_type n)
            noexcept(detail::has_nothrow_deallocate_v<Alloc>)
        {
            KTL_ASSERT(p != nullptr);
 
            m_Allocs -= n;
 
            if (p)
            {
                unsigned char* ptr = reinterpret_cast<unsigned char*>(p);
 
                size_t before = 0;
                size_t after = 0;
 
                // Check against corruption
                for (unsigned char* i = ptr - 1; i >= ptr - OVERFLOW_SIZE; i--)
                {
                    if (*i != OVERFLOW_TEST)
                        before = ptr - i;
                }
 
                for (unsigned char* i = ptr + n; i < ptr + n + OVERFLOW_SIZE; i++)
                {
                    if (*i != OVERFLOW_TEST)
                        after = i - ptr - n + 1;
                }
 
                if (before || after)
                {
                    m_Stream << "--------MEMORY CORRUPTION DETECTED--------\nThe area around " << p << " (" << n << " bytes) has been illegally modified\n";
 
                    if (before)
                        m_Stream << " Before (" << before << " bytes)\n";
 
                    if (after)
                        m_Stream << " After (" << after << " bytes)\n";
                }
 
                size_type size = n + OVERFLOW_SIZE * 2;
                m_Alloc.deallocate(ptr - OVERFLOW_SIZE, size);
            }
        }
#pragma endregion
 
#pragma region Construction
        template<typename T, typename... Args>
        void construct(T* p, Args&&... args) noexcept(
            (detail::has_construct_v<Alloc, T*, Args...> && detail::has_nothrow_construct_v<Alloc, T*, Args...>) ||
            std::is_nothrow_constructible_v<T, Args...>)
        {
            m_Constructs++;
 
            if constexpr (detail::has_construct_v<Alloc, T*, Args...>)
                m_Alloc.construct(p, std::forward<Args>(args)...);
            else
                ::new(p) T(std::forward<Args>(args)...);
        }
 
        template<typename T>
        void destroy(T* p) noexcept(
            (detail::has_destroy_v<Alloc, T*>&& detail::has_nothrow_destroy_v<Alloc, T*>) ||
            std::is_nothrow_destructible_v<T>)
        {
            m_Constructs--;
 
            if constexpr (detail::has_destroy_v<Alloc, T*>)
                m_Alloc.destroy(p);
            else
                p->~T();
        }
#pragma endregion
 
#pragma region Utility
        template<typename A = Alloc>
        typename std::enable_if<detail::has_max_size_v<A>, size_type>::type
        max_size() const
            noexcept(detail::has_nothrow_max_size_v<A>)
        {
            return m_Alloc.max_size();
        }
 
        template<typename A = Alloc>
        typename std::enable_if<detail::has_owns_v<A>, bool>::type
        owns(void* p) const
            noexcept(detail::has_nothrow_owns_v<A>)
        {
            return m_Alloc.owns(p);
        }
#pragma endregion
 
        Alloc& get_allocator() noexcept
        {
            return m_Alloc;
        }
 
        const Alloc& get_allocator() const noexcept
        {
            return m_Alloc;
        }
 
        Stream& get_stream() noexcept
        {
            return m_Stream;
        }
 
        const Stream& get_stream() const noexcept
        {
            return m_Stream;
        }
 
    private:
        Stream& m_Stream;
        KTL_EMPTY_BASE Alloc m_Alloc;
        int64_t m_Allocs;
        int64_t m_Constructs;
    };
}