Bug: 153120147

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  1. d1fefa5 Merge "Refresh Android.bp, cargo2android.json, TEST_MAPPING." by Joel Galenson · 6 weeks ago master
  2. b730a19 Refresh Android.bp, cargo2android.json, TEST_MAPPING. by Joel Galenson · 8 weeks ago
  3. b27d6cf Update TEST_MAPPING am: 2126573e27 am: 50d4598f29 am: 702b38976f by Joel Galenson · 5 months ago
  4. 702b389 Update TEST_MAPPING am: 2126573e27 am: 50d4598f29 by Joel Galenson · 5 months ago
  5. 50d4598 Update TEST_MAPPING am: 2126573e27 by Joel Galenson · 5 months ago android-s-v2-preview-1 android-s-v2-beta-2 android-s-v2-preview-2


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.


use rustc_hash::FxHashMap;

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


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.