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: vec_with_initialized.rs
    path of file: ./repos/tokio/tokio/src/io/util
    
    the code of the file until where you have to start completion: use crate::io::ReadBuf;
use std::mem::MaybeUninit;

/// Something that looks like a `Vec<u8>`.
///
/// # Safety
///
/// The implementor must guarantee that the vector returned by the
/// `as_mut` and `as_mut` methods do not change from one call to
/// another.
pub(crate) unsafe trait VecU8: AsRef<Vec<u8>> + AsMut<Vec<u8>> {}

unsafe im
    
    pub(crate) fn get_read_buf<'a>(&'a mut self) -> ReadBuf<'a> {
        let num_initialized = self.num_initialized;

        // SAFETY: Creating the slice is safe because of the safety invariants
        // on Vec<u8>. The safety invariants of `ReadBuf` will further guarantee
        // that no bytes in the slice are de-initialized.
        let vec = self.vec.as_mut();
        let len = vec.len();
        let cap = vec.capacity();
        let ptr = vec.as_mut_ptr().cast::<MaybeUninit<u8>>();
        let slice = unsafe { std::slice::from_raw_parts_mut::<'a, MaybeUninit<u8>>(ptr, cap) };

        // SAFETY: This is safe because the safety invariants of
        // VecWithInitialized say that the first num_initialized bytes must be
        // initialized.
        let mut read_buf = ReadBuf::uninit(slice);
        unsafe {
            read_buf.assume_init(num_initialized);
        }
        read_buf.set_filled(len);

        read_buf
    }