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: buf_reader.rs
    path of file: ./repos/phaser/phaser/vendor/tokio/src/io/util
    
    the code of the file until where you have to start completion: use crate::io::util::DEFAULT_BUF_SIZE;
use crate::io::{AsyncBufRead, AsyncRead, AsyncSeek, AsyncWrite, ReadBuf};

use pin_project_lite::pin_project;
use std::io::{self, IoSlice, SeekFrom};
use std::pin::Pin;
use std::task::{Context, Poll};
use std::{cmp, fmt, mem};

pin_project! {
    /// Th
    
    fn start_seek(self: Pin<&mut Self>, pos: SeekFrom) -> io::Result<()> {
        // We needs to call seek operation multiple times.
        // And we should always call both start_seek and poll_complete,
        // as start_seek alone cannot guarantee that the operation will be completed.
        // poll_complete receives a Context and returns a Poll, so it cannot be called
        // inside start_seek.
        *self.project().seek_state = SeekState::Start(pos);
        Ok(())
    }