Function layer_from_dir

atomic-repository/src/oci.rs:82–131

Build a gzipped tar layer from a directory's contents (recursive). Paths inside the tar are relative to `dir`. Regular files and symlinks are included; directory entries themselves are omitted (their paths are implied by the files within). Entries are emitted in a deterministic (sorted) order. Computes `diff_id` (sha256 of the uncompressed tar stream) and `digest` (sha256 of the gzipped bytes).

(dir: &Path)

/// Computes `diff_id` (sha256 of the uncompressed tar stream) and `digest`
/// (sha256 of the gzipped bytes).
pub fn layer_from_dir(dir: &Path) -> std::io::Result<OciLayer> {
    let mut entries: Vec<(String, PathBuf, bool)> = Vec::new();
    for entry in WalkDir::new(dir) {
        let entry = entry.map_err(std::io::Error::from)?;
        let file_type = entry.file_type();
        if file_type.is_dir() {
            continue;
        }
        let rel = match entry.path().strip_prefix(dir) {
            Ok(r) => r,
            Err(_) => continue,
        };
        if rel.as_os_str().is_empty() {
            continue;
        }
        entries.push((
            rel.to_string_lossy().into_owned(),
            entry.path().to_path_buf(),
            file_type.is_symlink(),
        ));
    }
    entries.sort_by(|a, b| a.0.cmp(&b.0));

    let mut tar_buf = Vec::new();
    {
        let mut builder = Builder::new(&mut tar_buf);
        for (rel, full, is_symlink) in &entries {
            if *is_symlink {
                let target = std::fs::read_link(full)?;
                let mut header = Header::new_gnu();
                header.set_entry_type(EntryType::Symlink);
                header.set_size(0);
                header.set_mode(0o777);
                header.set_mtime(0);
                builder.append_link(&mut header, rel, &target)?;
            } else {
                let data = std::fs::read(full)?;
                let mut header = Header::new_gnu();
                header.set_entry_type(EntryType::Regular);
                header.set_size(data.len() as u64);
                header.set_mode(0o644);
                header.set_mtime(0);
                builder.append_data(&mut header, rel, data.as_slice())?;
            }
        }
        builder.finish()?;
    }

    finish_layer(tar_buf)
}

/// Build a single layer from an in-memory set of `(relative_path, bytes)` files
/// plus optional whiteouts.