use crate::pack::data::File;use git_object::{owned, SHA1_SIZE};use quick_error::quick_error; quick_error! {    #[derive(Debug)]    pub enum Error {        Mismatch { expected: owned::Id, actual: owned::Id } {            display("pack checksum mismatch: expected {}, got {}", expected, actual)        }        Io(err: std::io::Error) {            display("could not read pack file")            from()            source(err)        }    }} /// Checksums and verify checksumsimpl File {    pub fn checksum(&self) -> owned::Id {        owned::Id::from_20_bytes(&self.data[self.data.len() - SHA1_SIZE..])    }    pub fn verify_checksum(&self) -> Result<owned::Id, Error> {        let mut hasher = git_features::hash::Sha1::default();         let actual = match std::fs::File::open(&self.path) {            Ok(mut pack) => {                use std::io::Read;                const BUF_SIZE: usize = u16::MAX as usize;                let mut buf = [0u8; BUF_SIZE];                let mut bytes_left = self.data.len() - SHA1_SIZE;                while bytes_left > 0 {                    let out = &mut buf[..BUF_SIZE.min(bytes_left)];                    pack.read_exact(out)?;                    bytes_left -= out.len();                    hasher.update(out);                }                owned::Id::new_sha1(hasher.digest())            }            Err(_) => {                let right_before_trailer = self.data.len() - SHA1_SIZE;                hasher.update(&self.data[..right_before_trailer]);                owned::Id::new_sha1(hasher.digest())            }        };         let expected = self.checksum();        if actual == expected {            Ok(actual)        } else {            Err(Error::Mismatch { actual, expected })        }    }}