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: resolve.rs
    path of file: ./repos/rust-ipfs/unixfs/examples
    
    the code of the file until where you have to start completion: use cid::Cid;
use ipfs_unixfs::dir::{resolve, LookupError, ResolveError};
use std::convert::TryFrom;
use std::fmt;
use std::io::{Error as IoError, Read};
use std::path::PathBuf;

fn main() {
    let path = match std::env::args()
        .nth(1)
        .map(|s| IpfsPath::try_from(s.as_str()))
    {
        Some(Ok(path)) => path,
        Some(Err(e)) => {
            eprintln!("Invalid path given as argument: {}", e);
            std::process::exit(1);
        }
        None => {
            eprintln!("USAGE: {} IPFSPATH\n", std::env::args().next().unwrap());
            eprintln!(
                "Will resolve the given IPFSPATH to a CID through any UnixFS \
                directories or HAMT shards from default go-ipfs 0.5 \
                configuration flatfs blockstore and write the final CID into \
                stdout"
            );
            std::process::exit(0);
        }
    };

    let ipfs_path = match std::env::var("IPFS_PATH") {
        Ok(s) => s,
        Err(e) => {
            eprintln!("IPFS_PATH is not set or could not be read: {}", e);
            std::process::exit(1);
        }
    };

    let mut blocks = PathBuf::from(ipfs_path);
    blocks.push("blocks");

    let blockstore = ShardedBlockStore { root: blocks };

    match walk(blockstore, path) {
        Ok(Some(cid)) => {
            println!("{}", cid);
        }
        Ok(None) => {
            eprintln!("not found");
        }
        Err(Error::OpeningFailed(e)) => {
            eprintln!("{}\n", e);
            eprintln!("This is likely caused by either:");
            eprintln!(" - ipfs does not have the block");
            eprintln!(" - ipfs is configured to use non-flatfs storage");
            eprintln!(" - ipfs is configured to use flatfs with different sharding");
            std::process::exit(1);
        }
        Err(e) => {
            eprintln!("Failed to walk the merkle tree: {}", e);
            std::process::exit(1);
        }
    }
}

#[derive(Debug)]
pub enum PathError {
    InvalidCid(cid::Error),
    InvalidPath,
}

impl fmt::Display for PathError {
    fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            PathError::InvalidCid(e) => write!(fmt, "{}", e),
            PathError::InvalidPath => write!(fmt, "invalid path"),
        }
    }
}

impl std::error::Error for PathError {}

/// Ipfs path following https://github.com/ipfs/go-path/
#[derive(Debug)]
pub struct IpfsPath {
    /// Option to support moving the cid
    root: Option<Cid>,
    path: std::vec::IntoIter<String>,
}

impl From<Cid> for IpfsPath {
    /// Creates a 
    
fn walk(blocks: ShardedBlockStore, mut path: IpfsPath) -> Result<Option<Cid>, Error> {
    use ipfs_unixfs::dir::MaybeResolved::*;

    let mut buf = Vec::new();
    let mut root = path.take_root().unwrap();

    let mut cache = None;

    for segment in path.path {
        println!("cache {:?}", cache);
        buf.clear();
        eprintln!("reading {} to resolve {:?}", root, segment);
        blocks.as_file(&root.to_bytes())?.read_to_end(&mut buf)?;

        let mut walker = match resolve(&buf, segment.as_str(), &mut cache)? {
            Found(cid) => {
                // either root was a Directory or we got lucky with a HAMT directory.
                // With HAMTDirectories the top level can contain a direct link to the target, but
                // it's more likely it will be found under some bucket, which would be the third
                // case in this match.
                println!("got lucky: found {} for {:?}", cid, segment);
                println!("cache {:?}", cache);
                root = cid;
                continue;
            }

            NotFound => return Ok(None),

            // when we stumble upon a HAMT shard, we'll need to look up other blocks in order to
            // find the final link. The current implementation cannot search for the directory by
            // hashing the name and looking it up, but the implementation can be changed underneath
            // without changes to the API.
            //
            // HAMTDirecotories or HAMT shards are multi-block directories where the entires are
            // bucketed per their hash value.
            NeedToLoadMore(walker) => walker,
        };

        eprintln!("walking {} on {:?}", root, segment);

        let mut other_blocks = 1;

        loop {
            let (first, _) = walker.pending_links();
            buf.clear();
            eprintln!("  -> reading {} while searching for {:?}", first, segment);
            blocks.as_file(&first.to_bytes())?.read_to_end(&mut buf)?;

            match walker.continue_walk(&buf, &mut cache)? {
                NotFound => {
                    println!("cache {:?}", cache);
                    return Ok(None);
                }
                Found(cid) => {
                    eprintln!(
                        "     resolved {} from {} after {} blocks to {}",
                        segment, root, other_blocks, cid
                    );
                    root = cid;
                    break;
                }
                NeedToLoadMore(next) => walker = next,
            }
            other_blocks += 1;
        }
    }

    println!("cache {:?}", cache);
    Ok(Some(root))
}