Struct PackIndexCache 

pub struct PackIndexCache { /* private fields */ }

In-process LRU cache of decoded pack indices keyed by (prefix, content-sha).

Capacity is bounded by byte size, not entry count: a single 1 GB pack carries an .idx file of multiple MiB, so an entry-count cap would either over- or under-budget for realistic chains. Eviction is least-recently-used.

The cache is Send + Sync and shareable across read_blob calls. Multiple concurrent calls block briefly on the inner mutex during lookup / insert; the inflate / range-GET work happens outside the lock so contention stays bounded.

LRU bookkeeping cost

get and insert walk the order VecDeque via iter().position to move the touched key to the back — O(n) in the cache size. For typical packchain workloads (single-digit indices in flight), the constant factor dominates and this is faster than a true O(1) linked-list LRU. If a workload starts seeing hundreds of cached indices, this should be revisited (e.g. swap to the lru crate or hand-roll a HashMap + intrusive doubly-linked list). The simple shape is intentional for now.

Example

use git_remote_object_store::{packchain::PackIndexCache, Remote};

let remote = Remote::connect("s3+https://bucket/repo?engine=packchain").await?;
let cache = PackIndexCache::default();
let bytes = git_remote_object_store::packchain::read_blob(
    &remote,
    "refs/heads/main",
    "src/main.rs",
    &cache,
).await?;
println!("{}", String::from_utf8_lossy(&bytes));

Implementations

impl PackIndexCache

pub fn new(capacity_bytes: u64) -> Self

Construct a cache with the requested byte budget.

capacity_bytes of zero disables caching (every lookup misses). Use Self::default for the standard 64 MiB budget.

pub fn resident_bytes(&self) -> u64

Total resident bytes accounted for by the cache.

Panics

Panics only if a previous holder of the inner mutex panicked while mutating cache state — an invariant violation that would be unsafe to silently recover from.

pub fn len(&self) -> usize

Number of cached entries.

Panics

See Self::resident_bytes.

pub fn is_empty(&self) -> bool

Whether the cache currently holds zero entries.

Trait Implementations

impl Debug for PackIndexCache

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for PackIndexCache

fn default() -> Self

Returns the “default value” for a type.