use crate::pack::data::File;use git_features::progress::Progress;use git_hash::SIZE_OF_SHA1_DIGEST as SHA1_SIZE;use git_object::{owned, HashKind}; /// Returned by [`File::verify_checksum()`]#[derive(thiserror::Error, Debug)]#[allow(missing_docs)]pub enum Error {    #[error("pack checksum mismatch: expected {expected}, got {actual}")]    Mismatch { expected: owned::Id, actual: owned::Id },    #[error("could not read pack file")]    Io(#[from] std::io::Error),} /// Checksums and verify checksumsimpl File {    /// The checksum in the trailer of this pack data file    pub fn checksum(&self) -> owned::Id {        owned::Id::from_20_bytes(&self.data[self.data.len() - SHA1_SIZE..])    }     /// Verifies that the checksum of the packfile over all bytes preceding it indeed matches the actual checksum,    /// returning the actual checksum equivalent to the return value of [`checksum()`][File::checksum()] if there    /// is no mismatch.    ///    /// Note that if no `progress` is desired, one can pass [`git_features::progress::Discard`].    ///    /// Have a look at [`index::File::verify_integrity(…)`][crate::pack::index::File::verify_integrity()] for an    /// even more thorough integrity check.    pub fn verify_checksum(&self, mut progress: impl Progress) -> Result<owned::Id, Error> {        let right_before_trailer = self.data.len() - SHA1_SIZE;        let actual =            match git_features::hash::bytes_of_file(&self.path, right_before_trailer, HashKind::Sha1, &mut progress) {                Ok(id) => id,                Err(_io_err) => {                    let start = std::time::Instant::now();                    let mut hasher = git_features::hash::Sha1::default();                    hasher.update(&self.data[..right_before_trailer]);                    progress.inc_by(right_before_trailer);                    progress.show_throughput(start);                    owned::Id::new_sha1(hasher.digest())                }            };         let expected = self.checksum();        if actual == expected {            Ok(actual)        } else {            Err(Error::Mismatch { actual, expected })        }    }}