Function compare_digests

alpm-package/src/input.rs:187–246

Compares the hash digest of a file with the recorded data in an [`Mtree`]. Takes an `mtree` against which a `file_name` in `input_dir` is checked. Returns the absolute path to the file and a byte buffer that represents the contents of the file. # Errors Returns an error if - the file path (`input_dir` + `file_name`) does not exist, - the file can not be read, - the hash digest of the file does

(
    mtree: &Mtree,
    input_dir: &InputDir,
    file_name: &str,
)

/// - the hash digest of the file does not match that initially recorded in `mtree`,
/// - or the file can not be found in `mtree`.
fn compare_digests(
    mtree: &Mtree,
    input_dir: &InputDir,
    file_name: &str,
) -> Result<(PathBuf, Vec<u8>), crate::Error> {
    let path = input_dir.join(file_name);

    if !path.exists() {
        return Err(Error::FileIsMissing {
            path: PathBuf::from(file_name),
            input_dir: input_dir.to_path_buf(),
        }
        .into());
    }

    // Read the file to a buffer.
    let buf = read(path.as_path()).map_err(|source| crate::Error::IoPath {
        path: path.clone(),
        context: t!("error-io-read-file"),
        source,
    })?;

    // Create a custom file name for searching in ALPM-MTREE entries, as they are prefixed with
    // MTREE_PATH_PREFIX.
    let mtree_file_name = PathBuf::from(MTREE_PATH_PREFIX).join(file_name);

    // Create a SHA-256 hash digest for the file.
    let current_digest = Sha256Checksum::calculate_from(&buf);

    // Check if the initial hash digest of the file - recorded in ALPM-MTREE data - matches.
    if let Some(initial_digest) = match mtree {
        Mtree::V1(paths) => paths.as_slice(),
        Mtree::V2(paths) => paths.as_slice(),
    }
    .iter()
    .find_map(|path| match path {
        alpm_mtree::mtree::v2::Path::File(file) if file.path == mtree_file_name => {
            Some(file.sha256_digest.clone())
        }
        _ => None,
    }) {
        if initial_digest != current_digest {
            return Err(Error::FileHashDigestChanged {
                path: PathBuf::from(file_name),
                current_digest,
                initial_digest,
                input_dir: input_dir.to_path_buf(),
            }
            .into());
        }
    } else {
        return Err(Error::FileIsMissing {
            path: PathBuf::from(file_name),
            input_dir: input_dir.to_path_buf(),
        }
        .into());
    };