linear_allocator.hpp

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#pragma once
 
#include <cstddef>
#include <memory>
 
#include <co_ecs/detail/bits.hpp>
 
namespace co_ecs::detail {
 
class linear_allocator {
public:
    explicit constexpr linear_allocator(void* ptr, std::size_t size) noexcept : _ptr(ptr), _head(ptr), _size(size) {
    }
 
    linear_allocator(const linear_allocator&) = delete;
 
    linear_allocator& operator=(const linear_allocator&) = delete;
 
    linear_allocator(linear_allocator&&) = default;
 
    linear_allocator& operator=(linear_allocator&&) = default;
 
    auto allocate(std::size_t size, std::size_t alignment = alignof(std::max_align_t)) noexcept -> void* {
        assert(is_power_of_2(alignment) && "Alignment must be a power of two");
 
        auto space_left = _size - (static_cast<char*>(_head) - static_cast<char*>(_ptr));
        auto ptr = std::align(alignment, size, _head, space_left);
        if (!ptr) {
            return nullptr;
        }
        _head = static_cast<char*>(ptr) + size;
        return ptr;
    }
 
    constexpr void reset() noexcept {
        _head = _ptr;
    }
 
private:
    void* _head;
    void* _ptr;
    std::size_t _size;
};
 
 
} // namespace co_ecs::detail