Struct DecompressedChunkCache 

pub struct DecompressedChunkCache { /* private fields */ }

A shared, bytes-bounded, sharded decompressed-chunk cache.

Implementations

impl DecompressedChunkCache

pub fn with_budget_bytes(total_budget_bytes: usize) -> Self

Create a cache with total_budget_bytes split across DEFAULT_SHARDS shards.

pub fn with_budget_and_shards( total_budget_bytes: usize, shard_count: usize, ) -> Self

Create a cache with total_budget_bytes split across shard_count shards.

shard_count is rounded UP to the next power of two (min 1) so shard selection can mask instead of modulo. Unit tests use shard_count = 1 for deterministic eviction ordering; production uses DEFAULT_SHARDS.

pub fn disabled() -> Self

Create a genuine no-op cache (issue #1568): reads bypass it entirely.

Used when config.memory.block_cache.enabled == false so the advertised toggle really disables caching instead of being decorative. get always returns None (no counters touched), insert returns the Arc without retaining it, and resident_bytes() / len() / budget_bytes() all report 0. A single dummy shard is allocated only so shard indexing stays valid; nothing is ever stored in it.

pub fn get(&self, key: &ChunkKey) -> Option<Bytes>

Look up a resident chunk. On a hit this bumps recency and returns a Bytes::clone (refcount bump, no chunk-sized allocation). On a miss returns None.

pub fn insert(&self, key: ChunkKey, data: Vec<u8>) -> Bytes

Insert data under key, returning the resident Bytes.

The Vec<u8> is converted to Bytes exactly once here via Bytes::from, which is ZERO-COPY: it takes ownership of the Vec’s existing heap allocation rather than allocating a new backing store and copying (issue #1940 substrate). The returned handle and any subsequent get share that one buffer (refcount-bumped clones). After insertion the owning shard evicts LRU entries until it is within its byte budget (never evicting the just-inserted entry).

pub fn resident_bytes(&self) -> usize

Total resident decompressed bytes across all shards.

pub fn len(&self) -> usize

Total resident entry count across all shards.

pub fn is_empty(&self) -> bool

Whether the cache currently holds no entries.

pub fn budget_bytes(&self) -> usize

The configured total byte budget (budget_per_shard * shard count).

A disabled no-op cache reports 0 (it holds nothing).

pub fn hit_count(&self) -> u64

Cumulative cache hits (test/observability instrumentation).

pub fn miss_count(&self) -> u64

Cumulative cache misses (test/observability instrumentation).

pub fn eviction_count(&self) -> u64

Cumulative entries evicted to stay within budget (issue #1571, B5).

Real relaxed-atomic counter; a disabled no-op cache never evicts and reports 0.

Trait Implementations

impl Debug for DecompressedChunkCache

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

Formats the value using the given formatter.

impl Default for DecompressedChunkCache

fn default() -> Self

Returns the “default value” for a type.