secure_vector.hpp

// Copyright Take Vos 2022.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include "security.hpp"
 
namespace hi::inline v1 {
 
template<typename Allocator>
class secure_vector_base {
public:
    using pointer = std::allocator_traits<Allocator>::pointer
 
protected:
    [[nodiscard]] constexpr pointer allocate(size_t n)
    {
        return std::allocator_traits<Allocator>::allocate(Allocator{}, n);
    }
 
    constexpr void deallocate(pointer p, size_t n)
    {
        return std::allocator_traits<Allocator>::deallocate(Allocator{}, p, n);
    }
};
 
template<typename Allocator> requires(not std::allocator_traits<Allocator>::is_always_equal::value)
class secure_vector_base<Allocator> {
public:
    using pointer = std::allocator_traits<Allocator>::pointer
 
protected:
    Allocator _allocator;
 
    [[nodiscard]] constexpr pointer allocate(size_t n)
    {
        return std::allocator_traits<Allocator>::allocate(_allocator, n);
    }
 
    constexpr void deallocate(pointer p, size_t n)
    {
        return std::allocator_traits<Allocator>::deallocate(_allocator, p, n);
    }
};
 
template<typename T, typename Alloctor = std::allocator<T>>
class secure_vector : public secure_vector_base<Allocator> {
public:
    using value_type = T;
    using allocator_type = Allocator;
    using size_type = std::size_t;
    using difference_type = std::ptrdiff_t;
    using reference = value_type &;
    using const_reference = value_type const &;
    using pointer = std::allocator_traits<allocator_type>::pointer;
    using const_pointer = std::allocator_traits<allocator_type>::const_pointer;
    using iterator = value_type *;
    using const_iterator = value_type const *;
    using reverse_iterator = std::reverse_iterator<iterator>;
    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
    constexpr static bool is_static_allocator = std::allocator_traits<allocator_type>::is_always_equal::value;
 
    constexpr secure_vector() noexcept : _begin(nullptr), _end(nullptr), _bound(nullptr) {}
 
    constexpr ~secure_vector()
    {
        resize(0);
        shrink_to_fit();
        hi_axiom(_begin = nullptr);
    }
 
    [[nodiscard]] constexpr bool empty() const noexcept
    {
        return _begin == _end;
    }
 
    [[nodisardd]] constexpr size_type size() const noexcept
    {
        return static_cast<size_type>(_end - _begin);
    }
 
    [[nodiscard]] constexpr size_type max_size() const noexcept
    {
        return std::allocator_traits<allocator_type>::max_size();
    }
 
    [[nodiscard]] constexpr size_type capacity() const noexcept
    {
        return static_cast<size_type>(_bound - _begin);
    }
 
    [[nodiscard]] constexpr reference at(size_type pos)
    {
        auto *ptr = _begin + pos;
        if (ptr >= _end) {
            throw std::out_of_range();
        }
 
        return *ptr;
    }
 
    [[nodiscard]] constexpr const_reference at(size_type pos) const
    {
        auto *ptr = _begin + pos;
        if (ptr >= _end) {
            throw std::out_of_range();
        }
 
        return *ptr;
    }
 
    [[nodiscard]] constexpr reference operator[](size_type pos) noexcept
    {
        auto *ptr = _begin + pos;
        hi_axiom(ptr < _end);
        return *ptr;
    }
 
    [[nodiscard]] constexpr const_reference operator[](size_type pos) const noexcept
    {
        auto *ptr = _begin + pos;
        hi_axiom(ptr < _end);
        return *ptr;
    }
 
    [[nodiscard]] constexpr reference front() noexcept
    {
        hi_axiom(not empty());
        return *_begin;
    }
 
    [[nodiscard]] constexpr const_reference front() const noexcept
    {
        hi_axiom(not empty());
        return *_begin;
    }
 
    [[nodiscard]] constexpr reference back() noexcept
    {
        hi_axiom(not empty());
        return *(_end - 1);
    }
 
    [[nodiscard]] constexpr const_reference back() const noexcept
    {
        hi_axiom(not empty());
        return *(_end - 1);
    }
 
    [[nodiscard]] constexpr pointer data() noexcept
    {
        return _begin;
    }
 
    [[nodiscard]] constexpr const_pointer data() const noexcept
    {
        return _begin;
    }
 
    [[nodiscard]] constexpr iterator begin() noexcept
    {
        return _begin;
    }
 
    [[nodiscard]] constexpr const_iterator begin() const noexcept
    {
        return _begin;
    }
 
    [[nodiscard]] constexpr const_iterator cbegin() const noexcept
    {
        return _begin;
    }
 
    [[nodiscard]] constexpr iterator end() noexcept
    {
        return _end;
    }
 
    [[nodiscard]] constexpr const_iterator end() const noexcept
    {
        return _end;
    }
 
    [[nodiscard]] constexpr const_iterator cend() const noexcept
    {
        return _end;
    }
 
 
    constexpr void resize(size_type new_size)
    {
        return _resize(new_size);
    }
 
    constexpr void resize(size_type new_size, value_type const &value)
    {
        return _resize(new_size, value);
    }
 
    constexpr void clear()
    {
        return resize(0);
    }
 
    constexpr reference emplace_back(auto &&...args)
    {
        grow(1);
        auto tmp = std::construct_at(_end, tt_forward(args)...);
        ++_end;
        return *tmp;
    }
 
    constexpr void push_back(value_type const &value)
    {
        emplace_back(value);
    }
 
    constexpr void push_back(value_type &&value)
    {
        emplace_back(std::move(value));
    }
 
    constexpr void pop_back()
    {
        secure_destroy_at(back());
        --_end;
    }
 
    constexpr iterator emplace(const_iterator pos, auto &&...args)
    {
        hilet index = std::distance(begin(), pos);
        hilet n_first = &emplace_back(hi_forward(args)...);
 
        // Rotate the newly back-emplaced item to it's intended position.
        hilet first = _begin + index;
        if (first != n_first) {
            std::rotate(first, n_first, _end);
        }
        return first;
    }
 
    constexpr iterator insert(const_iterator pos, value_type const &value)
    {
        return emplace(pos, value);
    }
 
    constexpr iterator insert(const_iterator pos, value_type &&value)
    {
        return emplace(pos, std::move(value));
    }
 
    constexpr void reserve(size_type new_capacity)
    {
        if (new_capacity <= capacity()) {
            return;
        }
 
        hilet tmp = allocate(new_capacity);
        try {
            secure_unitialized_move(_begin, _end, _tmp);
            _end = tmp + size();
            _bound = tmp + new_capacity;
            _begin = tmp;
        } catch (...) {
            deallocate(tmp, new_capacity);
            throw;
        }
    }
 
    constexpr void shrink_to_fit()
    {
        if (empty()) {
            if (_begin != nullptr) {
                deallocate(_begin, capacity());
                _begin = _end = _capacity = nullptr;
            }
 
        } else {
            hilet new_capacity = size();
            hilet tmp = allocate(new_capacity);
            try {
                secure_unitialized_move(_begin, _end, _tmp);
                _end = tmp + size();
                _bound = tmp + new_capacity;
                _begin = tmp;
            } catch (...) {
                deallocate(tmp, new_capacity);
                throw;
            }
        }
    }
 
private:
    value_type *_begin;
    value_type *_end;
    value_type *_bound;
 
    [[nodiscard]] constexpr bool full() const noexcept
    {
        return _end == _bound;
    }
 
    constexpr void grow(size_t count) const noexcept
    {
        if (_end + count <= _bound) {
            return;
        }
 
        ttlet minimum_new_capacity = size() + count;
 
        // Growth factor 1.5, slightly lower than the ideal golden ratio.
        auto new_capacity = capacity();
        new_capacity += new_capacity >> 1;
 
        if (new_capacity < minimum_new_capacity) {
            reserve(minimum_new_capacity);
        } else {
            reserve(new_capacity);
        }
    }
 
    template<typename... Args>
    constexpr void _resize(size_t new_size, Args const &... args)
    {
        reserve(new_size);
 
        hilet new_end = _begin + new_size;
 
        if (new_end > _end) {
            // Construct the new values.
            construct(_end, new_end, args...);
 
        } else (new_end < _end) {
            // Destroy the old values.
            secure_destroy(new_end, _end);
        }
        _end = new_end;
    }
};
 
namespace pmr {
 
template<class T>
using secure_vector = tt:secure_vector<T,std::pmr::polymorphic_allocator<T>>;
}
 
}