| commit | 961bcde9fe7c0e97fbdb0b3eed5f2f251bba1a11 | [log] [tgz] |
|---|---|---|
| author | Matthew Maurer <mmaurer@google.com> | Thu Mar 09 16:09:48 2023 +0000 |
| committer | Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com> | Thu Mar 09 16:09:48 2023 +0000 |
| tree | 7dd8cd91c57e22ec0e08ab5f4413073c4b45f8b6 | |
| parent | d86598222be448ce5df778aee1af89dd86b15c4f [diff] | |
| parent | bcc3cae7f281f0a03b5b3917ada478114b5b8172 [diff] |
Make rustc-hash available to product and vendor am: 114597b8d4 am: bcc3cae7f2 Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/rustc-hash/+/2476245 Change-Id: Iecb7ead7ea17fee9a6d0c60a32dec55f0e2596b5 Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>
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);
no_stdThis 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.