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WeakMap and WeakSet kept each collection's entries in one list and found a key by walking it, and every collection's entries for a key in 1,024 shared buckets. Filling a collection and reading it back took quadratic time: 40,000 keys took 6.7 s against Node's 0.2 s, and 200,000 keys did not finish. Each thread now indexes its entries twice, in open-addressing tables with linear probing and backward-shift deletion: by collection, key and kind, for get, set, has and delete, and by key pointer, for a key's disposal, which ends the key's entries in every collection. A collection's entries and a key's entries are doubly linked, so an entry leaves both in constant time. The tables grow at half load and are freed when their last entry goes, so an exiting worker leaves none. 200,000 keys now take 0.24 s (Node 0.30 s). Closes #1702 Co-authored-by: ejc3 <1694850+ejc3@users.noreply.github.com>
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| static inline size_t scr_weak_mix(uintptr_t bits) { | ||
| bits ^= bits >> 33; | ||
| bits *= 0xff51afd7ed558ccdull; | ||
| bits ^= bits >> 29; | ||
| return (size_t)bits; | ||
| } | ||
| static inline size_t scr_weak_entry_hash(const ScrWeakMap *owner, const void *key, unsigned kind) { | ||
| return scr_weak_mix((uintptr_t)key ^ ((uintptr_t)owner * 0x9E3779B97F4A7C15ull) ^ ((uintptr_t)kind << 56)); | ||
| } |
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On the supported wasm32-wasi target, the new weak-collection hashes shift 32-bit uintptr_t values by 33 and 56 bits, introducing undefined behavior into every weak-collection lookup and insertion.
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get,set,hasanddeletetake expected constant time.Closes #1702