76 lines
8.8 KiB
Plaintext
76 lines
8.8 KiB
Plaintext
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rust
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<EFBFBD>! #rustc 1.93.1 (01f6ddf75 2026-02-11)<29><02>ZF<5A>P<EFBFBD><50>v<EFBFBD><76><EFBFBD>]<5D>d9uu -4d8b4da6b4ab36bd<62> <02><05><11><><EFBFBD>GȬx<C8AC>92X<32>l -5bed970bceb2abc5<63> <02>.g<>:<3A><>Ld<4C><64>q<EFBFBD>T<EFBFBD>d -f090014afa110f38<33> <02>L<><4C><EFBFBD><EFBFBD><EFBFBD>l<EFBFBD>E,<07>R<EFBFBD><52> -3d16dd14375d91ab<61><02><11>b' ;<3B><>ݕ<EFBFBD><DD95>+<2B><>74 -cda84f9d48ee8a39<33> rustc_std_workspace_core<72><65><EFBFBD><EFBFBD><EFBFBD>7]<5D><><EFBFBD> <1F>}^ -d51aa419dcaa4806<30> hashbrown<77>\<5C><01><><EFBFBD>Y8
<0A> <0B>9!~ -828ad423d679028a<38> rustc_std_workspace_alloc<6F>)Z<7F><5A>T+@<15>U<EFBFBD><15><><EFBFBD> -456872f450a959d9<64>
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std_detect<EFBFBD><EFBFBD><<03>dpܞ.P\aܘ<61>L -20f4fe7d6fc49ef1<66> rustc_demangle<6C> $<24><><EFBFBD><EFBFBD><EFBFBD>.<2E>u
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@<40><>! -8707d0f6cef74754<35> windows_targets<74>aG<61>"T<>S<EFBFBD><53><02><> i -a000ab9e204fd71e<31> cfg_if<69>S]<5D><><EFBFBD><EFBFBD>]<5D><>8RH<52><48> -be85b4d8c54eea3b<33><02> <0C><08><><EFBFBD><EFBFBD>N<EFBFBD>}<7D>]<5D><>y^ -a8029966e34624a3<61> <02>,<2C> <02><<3C> <02>,<2C> |<7C> <00><> <02><<3C> <02><<3C> <02>,<2C> |<7C> <00><> <02>4<> <02><<3C> <02>,<2C> |<7C> <00><> BuildHasherDefault<6C><74><EFBFBD> <02>5<02>31/1 <02>$<24> <02>$<24> <02> FnvHasher<65>
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<02>
> with_key<65> finish<73> write<74> FnvBuildHasher<65>
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FnvHashMap<EFBFBD> K<> V<>
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FnvHashSet<EFBFBD> <02>
<02>
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<01> <02>
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<EFBFBD>3<EFBFBD><EFBFBD>R<EFBFBD><EFBFBD> <02>b<01>
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<02>
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<02>b<01><>
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# <01> . 5 <
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<02> <02><<3C> <02> <02> <02> <02>4<> <02>b <01><06><> <02>b <02><<3C> <01> <02><<3C> <01> <09> <00><> <00> H E An implementation of the [Fowler–Noll–Vo hash function][chongo].<2E> I <02> dM ## About<75> Z <02> <00>^J G The FNV hash function is a custom `Hasher` implementation that is more<72> <00><>$ ! efficient for smaller hash keys.<2E> <1C> <02> <00><>N K [The Rust FAQ states that][faq] while the default `Hasher` implementation,<2C> <00><>N K SipHash, is good in many cases, it is notably slower than other algorithms<6D> <00><>M J with short keys, such as when you have a map of integers to other values.<2E> <00><>> ; In cases like these, [FNV is demonstrably faster][graphs].<2E> <1C> <02> <00><>F C Its disadvantages are that it performs badly on larger inputs, and<6E> <00><>L I provides no protection against collision attacks, where a malicious user<65> <00><>G D can craft specific keys designed to slow a hasher down. Thus, it is<69> <00><>M J important to profile your program to ensure that you are using small hash<73> <00><>L I keys, and be certain that your program could not be exposed to malicious<75> <00><>0 - inputs (including being a networked server).<2E> <1C> <02> <00><>A > The Rust compiler itself uses FNV, as it is not worried about<75> <00><>M J denial-of-service attacks, and can assume that its inputs are going to be<62> <00><>' $ small—a perfect use case for FNV.<2E> <1C> <02><02> <1C> <0C> <00>
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## Using FNV in a `HashMap`
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The `FnvHashMap` type alias is the easiest way to use the standard library’s
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`HashMap` with FNV.
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```rust
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use fnv::FnvHashMap;
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let mut map = FnvHashMap::default();
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map.insert(1, "one");
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map.insert(2, "two");
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map = FnvHashMap::with_capacity_and_hasher(10, Default::default());
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map.insert(1, "one");
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map.insert(2, "two");
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```
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Note, the standard library’s `HashMap::new` and `HashMap::with_capacity`
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are only implemented for the `RandomState` hasher, so using `Default` to
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get the hasher is the next best option.
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## Using FNV in a `HashSet`
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Similarly, `FnvHashSet` is a type alias for the standard library’s `HashSet`
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with FNV.
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```rust
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use fnv::FnvHashSet;
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let mut set = FnvHashSet::default();
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set.insert(1);
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set.insert(2);
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set = FnvHashSet::with_capacity_and_hasher(10, Default::default());
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set.insert(1);
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set.insert(2);
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```
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<EFBFBD> <01><01><> <09> <01><> <09> <1C> <02> <00><>B ? [chongo]: http://www.isthe.com/chongo/tech/comp/fnv/index.html<6D> <00><>O L [faq]: https://www.rust-lang.org/en-US/faq.html#why-are-rusts-hashmaps-slow<6F> <00><>6 3 [graphs]: https://cglab.ca/~abeinges/blah/hash-rs/<2F>
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<02><13> <02><13> <02> <02><13> <02> <02> <02>b <01> <02>b <02>2 <01> <02>E <01> <04><> <13><04><>' <05><>$ 22EE<13> <00><>> ; An implementation of the Fowler–Noll–Vo hash function.<2E> <1C> <02> <00><>? < See the [crate documentation](index.html) for more details.<2E> L<> <00>
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<EFBFBD>3<EFBFBD><EFBFBD>R<EFBFBD><EFBFBD> <02>
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<EFBFBD> <13>1 <02>
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<EFBFBD>
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<1C>
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<00>
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Ե <00> <02> <00><> <<3C> <01>
t<> <00> <00><>& <00><>< 9 Create an FNV hasher starting with a state corresponding<6E> <00><> to the hash `key`.<2E>D<EFBFBD> <02>
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<EFBFBD>
key<65> <1C> <00><> <00> <02>b <02>b <00><> 4<> <1A> <00>
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<0C>
$<24> <00><>! ,<2C> <1B>
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<0C>
$<24> bytes<65>,<2C> <00><> <00><>& # A builder for default FNV hashers.<2E>t<EFBFBD> <02>b<02>b <02>b<01> <02>b<02><02>a MqA<71><41><EFBFBD><01> ̒ <00><> + ( A `HashMap` using a default FNV hasher.<2E><02> <1C> <0C> <0C> 8<02> <<3C> <0C> 7<02> ,<2C> <00><> T<> <01> <01> <02><> <01> <0C> <02><><01> <0C> <01><01> <02> <01> base<73><01> <00>!<21><>+&<26><01>(<01>(<01>&PR JL <00><> <00><> + ( A `HashSet` using a default FNV hasher.<2E><02> <1C> <0C> <0C> 8<02> <<3C> <0C> 7<02> ,<2C> <00><> T<> <02> <02><> <02> <0C> <01> <01> <02> <01> <01>'<01> <00><>nO<6E>"<22><><01>*<01>&68 <17><13><17><13> <0C> <13> 4http://www.isthe.com/chongo/tech/comp/fnv/index.html<6D>
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index.html<6D> FNV is demonstrably faster<65> (https://cglab.ca/~abeinges/blah/hash-rs/<2F> Fowler–Noll–Vo hash function<6F> crate documentation<6F> <01>* The Rust FAQ states that<61> (https://www.rust-lang.org/en-US/faq.html<6D> <01>* <01>* <01>* <01>+ <01>+ <01>+ <01>* <01>* <01>+ <01>* <01>* <01>+ <01>+ <01>+ <01>+ <00><>p<EFBFBD>`:.<2E><0F><><EFBFBD><7F>we<77>+<2B><>7m<37><6D><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><h<><68>k.<2E><>4,<03><>@<40>}<7D>f.<2E>El<45><6C> <1C><>K^<14>$P<>}<7D>6<EFBFBD>@<40>:)<29><>@<40><>6<EFBFBD><36><EFBFBD>ƣ<12>ϗ<EFBFBD> <1D>r<EFBFBD><72>,\<5C><>#_k<5F>Ӽ3<D3BC>
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<EFBFBD>"<22><><EFBFBD><EFBFBD>\<5C>q%4<><34>2<EFBFBD>qp<71><70><EFBFBD><EFBFBD><EFBFBD>bs<1B>R<EFBFBD><52><EFBFBD><EFBFBD><EFBFBD> WC:\Users\dxzq\.cargo\registry\src\mirrors.ustc.edu.cn-38d0e5eb5da2abae\fnv-1.0.7\lib.rs<72> 2<><17><>L(Y<><59><EFBFBD><EFBFBD>y<EFBFBD> <09><18><1B>Cn<43>X-<2D>0<EFBFBD><30><EFBFBD>& <00><><01><><01>I
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<0A>C <05> <02> <00># <00> !
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