3 [![crates.io](https://img.shields.io/crates/v/rustc-hash.svg)](https://crates.io/crates/rustc-hash)
4 [![Documentation](https://docs.rs/rustc-hash/badge.svg)](https://docs.rs/rustc-hash)
6 A speedy hash algorithm used within rustc. The hashmap in liballoc by
7 default uses SipHash which isn't quite as speedy as we want. In the
8 compiler we're not really worried about DOS attempts, so we use a fast
9 non-cryptographic hash.
11 This is the same as the algorithm used by Firefox -- which is a
12 homespun one not based on any widely-known algorithm -- though
13 modified to produce 64-bit hash values instead of 32-bit hash
14 values. It consistently out-performs an FNV-based hash within rustc
15 itself -- the collision rate is similar or slightly worse than FNV,
16 but the speed of the hash function itself is much higher because it
17 works on up to 8 bytes at a time.
22 use rustc_hash::FxHashMap;
24 let mut map: FxHashMap<u32, u32> = FxHashMap::default();
30 This crate can be used as a `no_std` crate by disabling the `std`
31 feature, which is on by default, as follows:
34 rustc-hash = { version = "1.0", default-features = false }
37 In this configuration, `FxHasher` is the only export, and the
38 `FxHashMap`/`FxHashSet` type aliases are omitted.