use git_features::progress::{self, Progress};use git_hash::SIZE_OF_SHA1_DIGEST as SHA1_SIZE;use git_object::{    bstr::{BString, ByteSlice},    immutable::object,    mutable,}; use crate::index;use std::{sync::atomic::AtomicBool, sync::Arc}; /// Returned by [`index::File::verify_checksum()`]#[derive(thiserror::Error, Debug)]#[allow(missing_docs)]pub enum Error {    #[error("index checksum mismatch: expected {expected}, got {actual}")]    Mismatch {        expected: git_hash::ObjectId,        actual: git_hash::ObjectId,    },    #[error("{kind} object {id} could not be decoded")]    ObjectDecode {        source: object::decode::Error,        kind: git_object::Kind,        id: git_hash::ObjectId,    },    #[error("{kind} object {id} wasn't re-encoded without change, wanted\n{expected}\n\nGOT\n\n{actual}")]    ObjectEncodeMismatch {        kind: git_object::Kind,        id: git_hash::ObjectId,        expected: BString,        actual: BString,    },    #[error(transparent)]    ObjectEncode(#[from] std::io::Error),} /// Various ways in which a pack and index can be verified#[derive(Debug, Eq, PartialEq, Hash, Clone, Copy)]pub enum Mode {    /// Validate SHA1 and CRC32    Sha1Crc32,    /// Validate SHA1 and CRC32, and decode each non-Blob object.    /// Each object should be valid, i.e. be decodable.    Sha1Crc32Decode,    /// Validate SHA1 and CRC32, and decode and encode each non-Blob object.    /// Each object should yield exactly the same hash when re-encoded.    Sha1Crc32DecodeEncode,} /// Verify and validate the content of the index fileimpl index::File {    /// Returns the trailing hash stored at the end of this index file.    ///    /// It's a hash over all bytes of the index.    pub fn index_checksum(&self) -> git_hash::ObjectId {        git_hash::ObjectId::from_20_bytes(&self.data[self.data.len() - SHA1_SIZE..])    }     /// Returns the hash of the pack data file that this index file corresponds to.    ///    /// It should [`crate::data::File::checksum()`] of the corresponding pack data file.    pub fn pack_checksum(&self) -> git_hash::ObjectId {        let from = self.data.len() - SHA1_SIZE * 2;        git_hash::ObjectId::from_20_bytes(&self.data[from..from + SHA1_SIZE])    }     /// Validate that our [`index_checksum()`][index::File::index_checksum()] matches the actual contents    /// of this index file, and return it if it does.    pub fn verify_checksum(        &self,        mut progress: impl Progress,        should_interrupt: &AtomicBool,    ) -> Result<git_hash::ObjectId, Error> {        let data_len_without_trailer = self.data.len() - SHA1_SIZE;        let actual = match git_features::hash::bytes_of_file(            &self.path,            data_len_without_trailer,            git_hash::Kind::Sha1,            &mut progress,            should_interrupt,        ) {            Ok(id) => id,            Err(_io_err) => {                let start = std::time::Instant::now();                let mut hasher = git_features::hash::Sha1::default();                hasher.update(&self.data[..data_len_without_trailer]);                progress.inc_by(data_len_without_trailer);                progress.show_throughput(start);                git_hash::ObjectId::new_sha1(hasher.digest())            }        };         let expected = self.index_checksum();        if actual == expected {            Ok(actual)        } else {            Err(Error::Mismatch { actual, expected })        }    }     /// The most thorough validation of integrity of both index file and the corresponding pack data file, if provided.    /// Returns the checksum of the index file, the traversal outcome and the given progress if the integrity check is successful.    ///    /// If `pack` is provided, it is expected (and validated to be) the pack belonging to this index.    /// It will be used to validate internal integrity of the pack before checking each objects integrity    /// is indeed as advertised via its SHA1 as stored in this index, as well as the CRC32 hash.    /// The last member of the Option is a function returning an implementation of [`crate::cache::DecodeEntry`] to be used if    /// the [`index::traverse::Algorithm`] is `Lookup`.    /// To set this to `None`, use `None::<(_, _, _, fn() -> crate::cache::Never)>`.    ///    /// The `thread_limit` optionally specifies the amount of threads to be used for the [pack traversal][index::File::traverse()].    /// `make_cache` is only used in case a `pack` is specified, use existing implementations in the [`crate::cache`] module.    ///    /// # Tradeoffs    ///    /// The given `progress` is inevitably consumed if there is an error, which is a tradeoff chosen to easily allow using `?` in the    /// error case.    pub fn verify_integrity<C, P>(        &self,        pack: Option<(            &crate::data::File,            Mode,            index::traverse::Algorithm,            impl Fn() -> C + Send + Sync,        )>,        thread_limit: Option<usize>,        progress: Option<P>,        should_interrupt: Arc<AtomicBool>,    ) -> Result<        (git_hash::ObjectId, Option<index::traverse::Outcome>, Option<P>),        index::traverse::Error<crate::index::verify::Error>,    >    where        P: Progress,        C: crate::cache::DecodeEntry,    {        let mut root = progress::DoOrDiscard::from(progress);        match pack {            Some((pack, mode, algorithm, make_cache)) => self                .traverse(                    pack,                    root.into_inner(),                    || {                        let mut encode_buf = Vec::with_capacity(2048);                        move |kind, data, index_entry, progress| {                            Self::verify_entry(mode, &mut encode_buf, kind, data, index_entry, progress)                        }                    },                    make_cache,                    index::traverse::Options {                        algorithm,                        thread_limit,                        check: index::traverse::SafetyCheck::All,                        should_interrupt,                    },                )                .map(|(id, outcome, root)| (id, Some(outcome), root)),            None => self                .verify_checksum(root.add_child("Sha1 of index"), &should_interrupt)                .map_err(Into::into)                .map(|id| (id, None, root.into_inner())),        }    }     #[allow(clippy::too_many_arguments)]    fn verify_entry<P>(        mode: Mode,        encode_buf: &mut Vec<u8>,        object_kind: git_object::Kind,        buf: &[u8],        index_entry: &index::Entry,        progress: &mut P,    ) -> Result<(), Error>    where        P: Progress,    {        if let Mode::Sha1Crc32Decode | Mode::Sha1Crc32DecodeEncode = mode {            use git_object::Kind::*;            match object_kind {                Tree | Commit | Tag => {                    let borrowed_object =                        git_object::immutable::Object::from_bytes(object_kind, buf).map_err(|err| {                            Error::ObjectDecode {                                source: err,                                kind: object_kind,                                id: index_entry.oid,                            }                        })?;                    if let Mode::Sha1Crc32DecodeEncode = mode {                        let object = mutable::Object::from(borrowed_object);                        encode_buf.clear();                        object.write_to(&mut *encode_buf)?;                        if encode_buf.as_slice() != buf {                            let mut should_return_error = true;                            if let git_object::Kind::Tree = object_kind {                                if buf.as_bstr().find(b"100664").is_some() || buf.as_bstr().find(b"100640").is_some() {                                    progress.info(format!("Tree object {} would be cleaned up during re-serialization, replacing mode '100664|100640' with '100644'", index_entry.oid));                                    should_return_error = false                                }                            }                            if should_return_error {                                return Err(Error::ObjectEncodeMismatch {                                    kind: object_kind,                                    id: index_entry.oid,                                    expected: buf.into(),                                    actual: encode_buf.clone().into(),                                });                            }                        }                    }                }                Blob => {}            };        }        Ok(())    }}