You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: mod.rs
    path of file: ./repos/glium/src/buffer
    
    the code of the file until where you have to start completion: //! A buffer is a memory location accessible to the video card.
//!
//! The purpose of buffers is to serve as a space where the GPU can read from or writ
    
    fn ref_from_ptr<'a>(ptr: *mut (), size: usize) -> Option<*mut [T]> {
        if size % mem::size_of::<T>() != 0 {
            return None;
        }

        let ptr = ptr as *mut T;
        let size = size / mem::size_of::<T>();
        Some(unsafe { slice::from_raw_parts_mut(&mut *ptr, size) as *mut [T] })
    }