Struct InternedStringMap 

pub struct InternedStringMap { /* private fields */ }

The short-string intern table, shaped like C-Lua’s stringtable (lstring.c): power-of-two hash buckets of GcRef<LuaString> chained by Vec instead of u.hnext. Compared to the previous HashMap<Box<[u8]>, GcRef<LuaString>>:

• lookup hashes the input bytes ONCE and never allocates (the entry-API shape boxed the key on every call — rejected experiment intern-hitpath-borrowed-lookup documents why a partial fix loses);
• insert reuses the same hash, no second probe;
• bytes are stored once (in the LuaString), not duplicated in a map key;
• dead strings are removed O(dead) by (hash, identity) pairs collected during the GC mark phase, replacing the O(table·log live) sort + binary-search retain that dominated churn-heavy profiles (concat_chain 20260609T2201Z: intern machinery ~25% of wall).

Implementations

impl InternedStringMap

pub fn len(&self) -> usize

pub fn is_empty(&self) -> bool

pub fn bucket_count(&self) -> usize

Number of hash buckets currently allocated (the power-of-two table size, C’s strt.size). Exposed for the shrink-policy test, which asserts the array grows under a flood and shrinks back toward 64 once the interned strings are collected.

pub fn find(&self, bytes: &[u8], hash: u32) -> Option<GcRef<LuaString>>

pub fn insert(&mut self, s: GcRef<LuaString>)

C’s luaS_resize growth rule: keep average chain length ~1.

pub fn shrink_if_sparse(&mut self)

C’s luaS_resize shrink path, driven by lgc.c:checkSizes (if (g->strt.nuse < g->strt.size / 4) luaS_resize(L, size/2)). Shrinks the bucket array when the live load factor falls below 25% (count * 4 < buckets.len()), down to next_power_of_two(count) floored at the initial 64 (C’s MINSTRTABSIZE). The 4× gap is hysteresis: a table at load factor just under 1.0 will not thrash, since the next grow-then-shrink cycle needs the population to drop fourfold first. Rehashing only relocates the surviving GcRef<LuaString> entries by their cached hash(); it never derefs a string, so it is safe to call from the post-mark/sweep GC hook AFTER all dead entries have been removed (only live refs remain).

pub fn remove(&mut self, hash: u32, identity: usize)

O(dead): removes one entry located by its cached hash + GC identity.

pub fn iter(&self) -> impl Iterator<Item = &GcRef<LuaString>>

pub fn contains_key(&self, bytes: &[u8]) -> bool

Trait Implementations

impl Default for InternedStringMap

fn default() -> Self

Returns the “default value” for a type.