Snap for 7168215 from 5f5d8f269f1b6302b2742b5f220cd106128e32d9 to simpleperf-release

Change-Id: I71193dc076eaf971f3c7d1ae1f59b53f5bfaff84
tree: 16244a35292a0f1c14f6fbc0d6998e7e774c4ad7
  1. .cargo_vcs_info.json
  2. .gitignore
  3. Android.bp
  4. CODE_OF_CONDUCT.md
  5. Cargo.toml
  6. Cargo.toml.orig
  7. LICENSE-APACHE
  8. LICENSE-MIT
  9. METADATA
  10. MODULE_LICENSE_APACHE2
  11. OWNERS
  12. README.md
  13. TEST_MAPPING
  14. src/
README.md

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.