use std::ops::DerefMut; use gix_object::Kind; /// A trait to model putting objects at a given pack `offset` into a cache, and fetching them.////// It is used to speed up [pack traversals][crate::index::File::traverse()].pub trait DecodeEntry {    /// Store a fully decoded object at `offset` of `kind` with `compressed_size` and `data` in the cache.    ///    /// It is up to the cache implementation whether that actually happens or not.    fn put(&mut self, pack_id: u32, offset: u64, data: &[u8], kind: gix_object::Kind, compressed_size: usize);    /// Attempt to fetch the object at `offset` and store its decoded bytes in `out`, as previously stored with [`DecodeEntry::put()`], and return    /// its (object `kind`, `decompressed_size`)    fn get(&mut self, pack_id: u32, offset: u64, out: &mut Vec<u8>) -> Option<(gix_object::Kind, usize)>;} /// A cache that stores nothing and retrieves nothing, thus it _never_ caches.#[derive(Default)]pub struct Never; impl DecodeEntry for Never {    fn put(&mut self, _pack_id: u32, _offset: u64, _data: &[u8], _kind: gix_object::Kind, _compressed_size: usize) {}    fn get(&mut self, _pack_id: u32, _offset: u64, _out: &mut Vec<u8>) -> Option<(gix_object::Kind, usize)> {        None    }} impl<T: DecodeEntry + ?Sized> DecodeEntry for Box<T> {    fn put(&mut self, pack_id: u32, offset: u64, data: &[u8], kind: Kind, compressed_size: usize) {        self.deref_mut().put(pack_id, offset, data, kind, compressed_size);    }     fn get(&mut self, pack_id: u32, offset: u64, out: &mut Vec<u8>) -> Option<(Kind, usize)> {        self.deref_mut().get(pack_id, offset, out)    }} /// A way of storing and retrieving entire objects to and from a cache.pub trait Object {    /// Put the object going by `id` of `kind` with `data` into the cache.    fn put(&mut self, id: gix_hash::ObjectId, kind: gix_object::Kind, data: &[u8]);     /// Try to retrieve the object named `id` and place its data into `out` if available and return `Some(kind)` if found.    fn get(&mut self, id: &gix_hash::ObjectId, out: &mut Vec<u8>) -> Option<gix_object::Kind>;} /// Various implementations of [`DecodeEntry`] using least-recently-used algorithms.#[cfg(any(feature = "pack-cache-lru-dynamic", feature = "pack-cache-lru-static"))]pub mod lru; pub mod object; /// Index-less parallel pack traversal.////// Build a delta [`delta::Tree`] directly from a streaming pack scan with/// [`delta::Tree::from_offsets_in_pack()`] — no pre-built `.idx` — then resolve every/// object in parallel with [`delta::Tree::traverse()`]. This is the index-less companion/// to the idx-verified [`crate::index::File::traverse_with_index()`]; [`delta::traverse::Context`] and/// [`delta::traverse::Options`] configure the traversal.////// ```no_run/// use gix_pack::cache::delta::Tree;/// use std::sync::atomic::AtomicBool;////// # fn build_index_less(/// #     pack_path: &std::path::Path,/// #     offsets: Vec<gix_pack::data::Offset>,/// # ) -> Result<(), Box<dyn std::error::Error>> {/// // Build the delta tree straight from the pack — no `.idx` required:/// let tree = Tree::from_offsets_in_pack(///     pack_path,///     offsets.into_iter(),///     &|offset| *offset,///     &|_id| None,                     // self-contained pack: no ref-delta lookups///     &mut gix_features::progress::Discard,///     &AtomicBool::default(),///     gix_hash::Kind::default(),/// )?;/// // `tree.traverse(resolve, &pack, pack_end, inspect, Options { .. })` then/// // resolves every object in parallel across threads./// let _ = tree;/// # Ok(()) }/// ```pub mod delta; /// Replaces content of the given `Vec` with the slice. The vec will have the same length/// as the slice. The vec can be either `&mut Vec` or `Vec`./// Returns `None` if no memory could be allocated.#[cfg(any(    feature = "pack-cache-lru-static",    feature = "pack-cache-lru-dynamic",    feature = "object-cache-dynamic"))]fn set_vec_to_slice<V: std::borrow::BorrowMut<Vec<u8>>>(mut vec: V, source: &[u8]) -> Option<V> {    let out = vec.borrow_mut();    out.clear();    out.try_reserve(source.len()).ok()?;    out.extend_from_slice(source);    Some(vec)}