internal representation of struct

[lenochware]

Hello, I have array of type vertex_t vertices[] where vertex_t is:

struct vertex_t {
  float[3] xyz;
  ubyte[4] color;
  ...
}

Now, I would like use instead of array "float[3] xyz" "vec3f xyz", where vec3f is:

struct vec3f {
  float x, y, z;

...some functions...
}

where I have defined some operators for adding and multipliing vectors etc.

Is it possible? "xyz" must be exactly 3 floats in memory because I am sending
vertices array pointer into OpenGL rendering pipeline.
Will be struct vec3f represented just like 3 floats - aren't here some
additional metadata - because structure contains also some functions?

My additional question: What about effectivity? I would like keep struct
vertex_t as simple as possible, because I need do calculations fast. Will have
replacing float array to structure some impact on speed?

Thank you.