#![allow(unused)] use std::path::{Path, PathBuf}; use crate::{File, State, decode, extension}; mod error {     /// The error returned by [File::at()][super::File::at()].    #[derive(Debug, thiserror::Error)]    #[expect(missing_docs)]    pub enum Error {        #[error("An IO error occurred while opening the index")]        Io(#[from] std::io::Error),        #[error(transparent)]        Decode(#[from] crate::decode::Error),        #[error(transparent)]        LinkExtension(#[from] crate::extension::link::decode::Error),    }} pub use error::Error; /// Initializationimpl File {    /// Try to open the index file at `path` with `options`, assuming `object_hash` is used throughout the file, or create a new    /// index that merely exists in memory and is empty. `skip_hash` will increase the performance by a factor of 2, at the cost of    /// possibly not detecting corruption.    ///    /// Note that the `path` will not be written if it doesn't exist.    pub fn at_or_default(        path: impl Into<PathBuf>,        object_hash: gix_hash::Kind,        skip_hash: bool,        options: decode::Options,    ) -> Result<Self, Error> {        let path = path.into();        Ok(match Self::at(&path, object_hash, skip_hash, options) {            Ok(f) => f,            Err(Error::Io(err)) if err.kind() == std::io::ErrorKind::NotFound => {                File::from_state(State::new(object_hash), path)            }            Err(err) => return Err(err),        })    }     /// Open an index file at `path` with `options`, assuming `object_hash` is used throughout the file. If `skip_hash` is `true`,    /// we will not get or compare the checksum of the index at all, which generally increases performance of this method by a factor    /// of 2 or more.    ///    /// Note that the verification of the file hash depends on `options`, and even then it's performed after the file was read and not    /// before it is read. That way, invalid files would see a more descriptive error message as we try to parse them.    pub fn at(        path: impl Into<PathBuf>,        object_hash: gix_hash::Kind,        skip_hash: bool,        options: decode::Options,    ) -> Result<Self, Error> {        let _span = gix_features::trace::detail!("gix_index::File::at()");        let path = path.into();        let (data, mtime) = {            let mut file = std::fs::File::open(&path)?;            // SAFETY: we have to take the risk of somebody changing the file underneath. Git never writes into the same file.            #[expect(unsafe_code)]            let data = unsafe { memmap2::MmapOptions::new().map_copy_read_only(&file)? };             if !skip_hash {                // Note that even though it's trivial to offload this into a thread, which is worth it for all but the smallest                // index files, we choose more safety here just like git does and don't even try to decode the index if the hashes                // don't match.                // Thanks to `skip_hash`, we can get performance and it's under caller control, at the cost of some safety.                let expected =                    gix_hash::ObjectId::from_bytes_or_panic(&data[data.len() - object_hash.len_in_bytes()..]);                if !expected.is_null() {                    let _span = gix_features::trace::detail!("gix::open_index::hash_index", path = ?path);                    let meta = file.metadata()?;                    let num_bytes_to_hash = meta.len() - object_hash.len_in_bytes() as u64;                    gix_hash::bytes(                        &mut file,                        num_bytes_to_hash,                        object_hash,                        &mut gix_features::progress::Discard,                        &Default::default(),                    )                    .map_err(|err| match err {                        gix_hash::io::Error::Io(err) => Error::Io(err),                        gix_hash::io::Error::Hasher(err) => Error::Decode(err.into()),                    })?                    .verify(&expected)                    .map_err(decode::Error::from)?;                }            }             (data, filetime::FileTime::from_last_modification_time(&file.metadata()?))        };         let (state, checksum) = State::from_bytes(&data, mtime, object_hash, options)?;        let mut file = File { state, path, checksum };        if let Some(mut link) = file.link.take() {            link.dissolve_into(&mut file, object_hash, skip_hash, options)?;        }         Ok(file)    }     /// Consume `state` and pretend it was read from `path`, setting our checksum to `null`.    ///    /// `File` instances created like that should be written to disk to set the correct checksum via `[File::write()]`.    pub fn from_state(state: State, path: impl Into<PathBuf>) -> Self {        File {            state,            path: path.into(),            checksum: None,        }    }}