Bug: 153120147

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  1. 8a30e28 Update TEST_MAPPING by Jeff Vander Stoep · 9 days ago master
  2. 631762c Merge "Update TEST_MAPPING" am: d09089c402 am: fda4ae1691 am: b9e389d827 am: 15c89bb590 by Treehugger Robot · 8 months ago main-16k-with-phones
  3. 15c89bb Merge "Update TEST_MAPPING" am: d09089c402 am: fda4ae1691 am: b9e389d827 by Treehugger Robot · 8 months ago
  4. b9e389d Merge "Update TEST_MAPPING" am: d09089c402 am: fda4ae1691 by Treehugger Robot · 8 months ago main-16k
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rustc-hash

crates.io Documentation

A speedy hash algorithm used within rustc. The hashmap in liballoc by default uses SipHash which isn‘t quite as speedy as we want. In the compiler we’re not really worried about DOS attempts, so we use a fast non-cryptographic hash.

This is the same as the algorithm used by Firefox -- which is a homespun one not based on any widely-known algorithm -- though modified to produce 64-bit hash values instead of 32-bit hash values. It consistently out-performs an FNV-based hash within rustc itself -- the collision rate is similar or slightly worse than FNV, but the speed of the hash function itself is much higher because it works on up to 8 bytes at a time.

Usage

use rustc_hash::FxHashMap;

let mut map: FxHashMap<u32, u32> = FxHashMap::default();
map.insert(22, 44);

no_std

This crate can be used as a no_std crate by disabling the std feature, which is on by default, as follows:

rustc-hash = { version = "1.0", default-features = false }

In this configuration, FxHasher is the only export, and the FxHashMap/FxHashSet type aliases are omitted.