Indexing and writing to a unique pointer like it is a normal pointer

Question

In my code I have the following:

struct alignas(16) sphere
{
    glm::vec4 center;
    glm::vec4 color;
    float radius;
};

sphere* m_sphere_ptr;

    m_sphere_ptr = static_cast<sphere*>(glMapNamedBufferRange(m_sphere_buffer, 0, m_spheres.size() * sizeof(sphere), GL_MAP_WRITE_BIT));


    auto sphere_x_offset { 5.0f };
    for (int index{ 0 }; index < m_spheres.size(); ++index)
    {
        float sphere_x { static_cast<float>(index) / m_spheres.size()};

        m_sphere_ptr[index].center = glm::vec4{ sphere_x + sphere_x_offset, -1, -5, 0 };
        m_sphere_ptr[index].color = m_spheres[index].color;
        m_sphere_ptr[index].radius = m_spheres[index].radius;
    }
    glUnmapNamedBuffer(m_sphere_buffer);

I want to change the sphere* m_sphere_ptr into a smart pointer. However, if I create it like: std::unique_ptr<sphere> m_sphere_ptr;

(and do not change any of my other code) I get a compilation error that m_sphere_ptr is not an array type.

Is there a safe way for me to index and and write to m_sphere_ptr when it is a unique pointer?

For reference glMapNamedBufferRange returns a void * which is why it is cast.

I just change `sphere* m_sphere_ptr;` to `std::unique_ptr m_sphere_ptr;` — Startec, May 06 '18 at 09:56
If it's an array type, wouldn't you have to tell `unique_ptr` about it so it knows to `delete []` it (and not use plain `delete`)? — melpomene, May 06 '18 at 10:00
You can use [`unique_ptr`](https://en.cppreference.com/w/cpp/memory/unique_ptr) to tell it you have an array. (Assuming it was allocated with `new[]`) — Bo Persson, May 06 '18 at 10:03
As `m_sphere_ptr ` is not allocated either with `new` or `new[]` (but with `glMapNamedBufferRange`) don't forget you will need a custom deleter. — Richard Critten, May 06 '18 at 10:06
fyi have a read of: https://stackoverflow.com/questions/17161013/raii-wrapper-for-opengl-objects — Richard Critten, May 06 '18 at 10:09

Indexing and writing to a unique pointer like it is a normal pointer

0 Answers0