//! a pack data fileuse filebuffer::FileBuffer;use std::{convert::TryInto, path::Path}; ///pub mod decode;mod header;pub use header::*; mod init;///pub mod parse;///pub mod verify; ///pub mod iter;pub use iter::Iter; use git_object::SHA1_SIZE; /// A slice into a pack file denoting a pack entry.////// An entry can be decoded into an object.pub type EntrySlice = std::ops::Range<u64>; /// Supported versions of a pack data file#[derive(PartialEq, Eq, Debug, Hash, Ord, PartialOrd, Clone, Copy)]#[cfg_attr(feature = "serde1", derive(serde::Serialize, serde::Deserialize))]#[allow(missing_docs)]pub enum Version {    V2,    V3,} /// A pack data filepub struct File {    data: FileBuffer,    path: std::path::PathBuf,    version: Version,    num_objects: u32,} /// Information about the pack data file itselfimpl File {    /// The pack data version of this file    pub fn version(&self) -> Version {        self.version    }    /// The number of objects stored in this pack data file    pub fn num_objects(&self) -> u32 {        self.num_objects    }    /// The length of all mapped data, including the pack header and the pack trailer    pub fn data_len(&self) -> usize {        self.data.len()    }     /// The position of the byte one past the last pack entry, or in other terms, the first byte of the trailing hash.    pub fn pack_end(&self) -> usize {        self.data.len() - SHA1_SIZE    }     /// The path to the pack data file on disk    pub fn path(&self) -> &Path {        &self.path    }     /// Returns the pack data at the given slice if its range is contained in the mapped pack data    pub fn entry_slice(&self, slice: EntrySlice) -> Option<&[u8]> {        let entry_end: usize = slice.end.try_into().expect("end of pack fits into usize");        let entry_start = slice.start as usize;        self.data.get(entry_start..entry_end)    }     /// Returns the CRC32 of the pack data indicated by `pack_offset` and the `size` of the mapped data.    ///    /// _Note:_ finding the right size is only possible by decompressing    /// the pack entry beforehand, or by using the (to be sorted) offsets stored in an index file.    ///    /// # Panics    ///    /// If `pack_offset` or `size` are pointing to a range outside of the mapped pack data.    pub fn entry_crc32(&self, pack_offset: u64, size: usize) -> u32 {        let pack_offset: usize = pack_offset.try_into().expect("pack_size fits into usize");        git_features::hash::crc32(&self.data[pack_offset..pack_offset + size])    }}