Commit Graph

35 Commits

Author SHA1 Message Date
Yuki Okushi
0765536c0b
Rollup merge of #78083 - ChaiTRex:master, r=m-ou-se
Stabilize or_insert_with_key

Stabilizes the `or_insert_with_key` feature from https://github.com/rust-lang/rust/issues/71024. This allows inserting key-derived values when a `HashMap`/`BTreeMap` entry is vacant.

The difference between this and  `.or_insert_with(|| ... )` is that this provides a reference to the key to the closure after it is moved with `.entry(key_being_moved)`, avoiding the need to copy or clone the key.
2020-12-19 15:15:57 +09:00
Chai T. Rex
f1b930d57c Improved documentation for HashMap/BTreeMap Entry's .or_insert_with_key method 2020-12-07 21:36:01 -05:00
Chai T. Rex
866ef87d3f Update rustc version that or_insert_with_key landed 2020-12-01 01:06:40 -05:00
Guillaume Gomez
ef32ef7baf
Rollup merge of #77996 - tkaitchuck:master, r=m-ou-se
Doc change: Remove mention of `fnv` in HashMap

Disclaimer: I am the author of [aHash](https://github.com/tkaitchuck/aHash).

This changes the Rustdoc in `HashMap` from mentioning the `fnv` crate to mentioning the `aHash` crate, as an alternative `Hasher` implementation.

### Why

Fnv [has poor hash quality](https://github.com/rurban/smhasher), is [slow for larger keys](https://github.com/tkaitchuck/aHash/blob/master/compare/readme.md#speed), and does not provide dos resistance, because it is unkeyed (this can also cause [other problems](https://accidentallyquadratic.tumblr.com/post/153545455987/rust-hash-iteration-reinsertion)).

Fnv has acceptable performance for integers and has very poor performance with keys >32 bytes. This is the reason it was removed from the standard library in https://github.com/rust-lang/rust/pull/37229 .

Because regardless of which dimension you value, there are better alternatives, it does not make sense for anyone to consider using `fnv`.

The text mentioning `fnv` in the standard library continues to create confusion: https://github.com/rust-lang/hashbrown/issues/153  https://github.com/rust-lang/hashbrown/issues/9 . There are also a number of [crates using it](https://crates.io/crates/fnv/reverse_dependencies) a great many of which are hashing strings (Which is when Fnv is the [worst](https://github.com/cbreeden/fxhash#benchmarks), [possible](https://github.com/tkaitchuck/aHash#speed), [choice](http://cglab.ca/~abeinges/blah/hash-rs/).)

I think aHash makes the most sense to mention as an alternative because it is the most credible option (in my obviously biased opinion). It offers [good performance on numbers and strings](https://github.com/tkaitchuck/aHash/blob/master/compare/readme.md#speed), is [of high quality](https://github.com/tkaitchuck/aHash#hash-quality), and [provides dos resistance](https://github.com/tkaitchuck/aHash/wiki/How-aHash-is-resists-DOS-attacks). It is popular (see [stats](https://crates.io/crates/ahash)) and is the default hasher for [hashbrown](https://crates.io/crates/hashbrown) and [dashmap](https://crates.io/crates/dashmap) which are the most popular alternative hashmaps. Finally it does not have any of the [`gotcha` cases](https://github.com/tkaitchuck/aHash#fxhash) that `FxHash` suffers from. (Which is the other popular hashing option when DOS attacks are not a concern)

Signed-off-by: Tom Kaitchuck <tom.kaitchuck@emc.com>
2020-11-13 15:26:10 +01:00
Tom Kaitchuck
4e5848349c
Update library/std/src/collections/hash/map.rs
Co-authored-by: Mara Bos <m-ou.se@m-ou.se>
2020-11-12 20:14:57 -08:00
Camelid
8258cf285f Convert a bunch of intra-doc links 2020-11-07 12:50:57 -08:00
Tom Kaitchuck
5b3d98d9f8 Change link to point to crates.io keyword "hasher"
Signed-off-by: Tom Kaitchuck <Tom.Kaitchuck@gmail.com>
2020-10-27 20:49:52 -07:00
Camelid
59f108885e Improve formatting of hash collections docs 2020-10-26 14:05:06 -07:00
Chai T. Rex
c2de8fe294 Stabilize or_insert_with_key 2020-10-18 15:45:09 -04:00
Tom Kaitchuck
1d287255f5 Change mention of fnv in HashMap to mention aHash as an alternitive hasher.
Signed-off-by: Tom Kaitchuck <tom.kaitchuck@emc.com>
2020-10-15 14:03:39 -07:00
Jonas Schievink
4ae7710e1d
Rollup merge of #77072 - sharnoff:hash-docs, r=LukasKalbertodt
Minor `hash_map` doc adjustments + item attribute orderings

This PR is really a couple visual changes glued together:
1. Some of the doc comments for items in `std::collections::hash_map` referenced the names of types without escaping their formatting (e.g. using "VacantEntry" instead of "`VacantEntry`") - the ones I could find were changed to the latter
2. The vast majority of pre-item attributes seem to place doc comments as the first attribute (instead of things like `#[feature(...)]`), so the few that had the other order were changed.
3. Also ordering related: the general trend seems to be that `#[feature]` attributes follow `#[inline]`, so I swapped the two lines in places where that ordering was reversed. This is primarily a change based on stylistic continuity and aesthetics - I'm not sure how important that actually is / should be.

I figured this would be pretty uncontroversial, but some of these might have been intentional for reasons I don't know about - if so, I'd be happy to remove the relevant changes. Of these, the final set of changes is probably the most unnecessary, so it also might be better to leave those out (in favor of reducing code churn).
2020-10-04 15:45:33 +02:00
Jonas Schievink
1118ab9930
Rollup merge of #75377 - canova:map_debug_impl, r=dtolnay
Fix Debug implementations of some of the HashMap and BTreeMap iterator types

HashMap's `ValuesMut`, BTreeMaps `ValuesMut`, IntoValues and `IntoKeys` structs were printing both keys and values on their Debug implementations. But they are iterators over either keys or values. Irrelevant values should not be visible. With this PR, they only show relevant fields.
This fixes #75297.

[Here's an example code.](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=0c79356ed860e347a0c1a205616f93b7) This prints this on nightly:
```
ValuesMut { inner: IterMut { range: [(1, "hello"), (2, "goodbye")], length: 2 } }
IntoKeys { inner: [(1, "hello"), (2, "goodbye")] }
IntoValues { inner: [(1, "hello"), (2, "goodbye")] }
[(2, "goodbye"), (1, "hello")]
```

After the patch this example prints these instead:
```
["hello", "goodbye"]
["hello", "goodbye"]
[1, 2]
["hello", "goodbye"]
```

I didn't add test cases for them, since I couldn't see any tests for Debug implementations anywhere. But please let me know if I should add it to a specific place.

r? @dtolnay
2020-10-03 00:31:04 +02:00
Waffle
1c2c336dbc Link new method in DefautHashers doc 2020-10-02 00:30:19 +03:00
Jonas Schievink
9ab95c36e2
Rollup merge of #76917 - GuillaumeGomez:map-missing-code-examples, r=Dylan-DPC
Add missing code examples on HashMap types

r? @Dylan-DPC
2020-09-27 01:53:13 +02:00
sharnoff
8a011b5da2 minor doc changes, attribute orderings 2020-09-22 19:34:05 +01:00
Guillaume Gomez
be3d8e5d6c Add missing code examples on HashMap types 2020-09-21 13:32:03 +02:00
Ralf Jung
f24d279084
Rollup merge of #76887 - GuillaumeGomez:hashset-iter-types-examples, r=Dylan-DPC
Add missing examples on HashSet iter types
2020-09-20 15:51:59 +02:00
Guillaume Gomez
28588e5df1 Add missing examples on HashSet iter types 2020-09-18 20:09:31 +02:00
Amjad Alsharafi
878dfa6718 Fixed intra-docs links in library/std/src/collections/hash/map.rs 2020-09-18 07:50:22 +08:00
Matt Brubeck
fb1fab5a67 Tests for HashMap/HashSet::drain_filter 2020-09-08 17:24:28 -07:00
Matt Brubeck
49aef963d3 Add HashMap::drain_filter and HashSet::drain_filter
Implements #59618.
2020-09-08 17:24:28 -07:00
Matt Brubeck
ebd15e790a Implement HashSet in terms of hashbrown::HashSet 2020-09-08 17:24:23 -07:00
Matt Brubeck
15ccdeb224 Update to hashbrown 0.9 2020-09-08 17:23:26 -07:00
bors
aa81d32165 Auto merge of #76128 - poliorcetics:doc-use-arc-clone, r=KodrAus
Use Arc::clone and Rc::clone in documentation

This PR replaces uses of `x.clone()` by `Rc::clone(&x)` (or `Arc::clone(&x)`) to better match the documentation for those types.

@rustbot modify labels: T-doc
2020-09-06 12:34:31 +00:00
Lzu Tao
a4e926daee std: move "mod tests/benches" to separate files
Also doing fmt inplace as requested.
2020-08-31 02:56:59 +00:00
Alexis Bourget
81e85ce76d Move to Arc::clone(&x) over x.clone() in library/std 2020-08-30 21:59:43 +02:00
Camelid
e9928d8926
Switch to intra-doc links in std::collections 2020-08-23 13:51:01 -07:00
Nazım Can Altınova
8faf550e5f
Remove the unused bounds from Debug impl of HashMap::{IntoKeys,IntoValues} 2020-08-11 20:42:02 +02:00
Nazım Can Altınova
456738e3d1
Only print values in the Debug of HashMap::ValuesMut struct 2020-08-10 23:06:04 +02:00
Nazım Can Altınova
4cd2637e2b
Update the tracking issue number of map_into_keys_values 2020-08-08 16:35:54 +02:00
Nazım Can Altınova
25545ed180
Only print the fields that are relevant to iterators for Debug of IntoKeys and IntoValues 2020-08-07 13:47:04 +02:00
Nazım Can Altınova
41dd4ee7ff
Add unit tests for new HashMap::into_{keys,values} methods 2020-08-07 13:13:41 +02:00
Nazım Can Altınova
e31116af50
Add into_{keys,values} methods for HashMap 2020-08-07 13:13:37 +02:00
Amanieu d'Antras
d51b7b229a Update hashbrown to 0.8.1 2020-08-07 07:03:12 +01:00
mark
2c31b45ae8 mv std libs to library/ 2020-07-27 19:51:13 -05:00