mirror of
https://gitee.com/openharmony/third_party_rust_rustc-hash
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fbcc679024
This version has already been published, yet the version change never arrived in the repo. Let's bump that in the Cargo.toml and README, so people don't copy old versions. Let's also fix a typo while we're here.
39 lines
1.3 KiB
Markdown
39 lines
1.3 KiB
Markdown
# rustc-hash
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[](https://crates.io/crates/rustc-hash)
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[](https://docs.rs/rustc-hash)
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A speedy hash algorithm used within rustc. The hashmap in liballoc by
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default uses SipHash which isn't quite as speedy as we want. In the
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compiler we're not really worried about DOS attempts, so we use a fast
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non-cryptographic hash.
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This is the same as the algorithm used by Firefox -- which is a
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homespun one not based on any widely-known algorithm -- though
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modified to produce 64-bit hash values instead of 32-bit hash
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values. It consistently out-performs an FNV-based hash within rustc
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itself -- the collision rate is similar or slightly worse than FNV,
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but the speed of the hash function itself is much higher because it
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works on up to 8 bytes at a time.
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## Usage
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```rust
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use rustc_hash::FxHashMap;
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let mut map: FxHashMap<u32, u32> = FxHashMap::default();
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map.insert(22, 44);
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```
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### `no_std`
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This crate can be used as a `no_std` crate by disabling the `std`
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feature, which is on by default, as follows:
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```toml
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rustc-hash = { version = "1.1", default-features = false }
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```
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In this configuration, `FxHasher` is the only export, and the
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`FxHashMap`/`FxHashSet` type aliases are omitted.
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