hashbrown/lib.rs
1//! This crate is a Rust port of Google's high-performance [SwissTable] hash
2//! map, adapted to make it a drop-in replacement for Rust's standard `HashMap`
3//! and `HashSet` types.
4//!
5//! The original C++ version of [SwissTable] can be found [here], and this
6//! [CppCon talk] gives an overview of how the algorithm works.
7//!
8//! [SwissTable]: https://abseil.io/blog/20180927-swisstables
9//! [here]: https://github.com/abseil/abseil-cpp/blob/master/absl/container/internal/raw_hash_set.h
10//! [CppCon talk]: https://www.youtube.com/watch?v=ncHmEUmJZf4
11
12#![no_std]
13#![cfg_attr(
14 feature = "nightly",
15 feature(
16 test,
17 core_intrinsics,
18 dropck_eyepatch,
19 min_specialization,
20 extend_one,
21 allocator_api,
22 slice_ptr_get,
23 maybe_uninit_array_assume_init,
24 strict_provenance
25 )
26)]
27#![allow(
28 clippy::doc_markdown,
29 clippy::module_name_repetitions,
30 clippy::must_use_candidate,
31 clippy::option_if_let_else,
32 clippy::redundant_else,
33 clippy::manual_map,
34 clippy::missing_safety_doc,
35 clippy::missing_errors_doc
36)]
37#![warn(missing_docs)]
38#![warn(rust_2018_idioms)]
39#![cfg_attr(feature = "nightly", warn(fuzzy_provenance_casts))]
40#![cfg_attr(feature = "nightly", allow(internal_features))]
41
42#[cfg(test)]
43#[macro_use]
44extern crate std;
45
46#[cfg_attr(test, macro_use)]
47extern crate alloc;
48
49#[cfg(feature = "nightly")]
50#[cfg(doctest)]
51doc_comment::doctest!("../README.md");
52
53#[macro_use]
54mod macros;
55
56#[cfg(feature = "raw")]
57/// Experimental and unsafe `RawTable` API. This module is only available if the
58/// `raw` feature is enabled.
59pub mod raw {
60 // The RawTable API is still experimental and is not properly documented yet.
61 #[allow(missing_docs)]
62 #[path = "mod.rs"]
63 mod inner;
64 pub use inner::*;
65
66 #[cfg(feature = "rayon")]
67 /// [rayon]-based parallel iterator types for hash maps.
68 /// You will rarely need to interact with it directly unless you have need
69 /// to name one of the iterator types.
70 ///
71 /// [rayon]: https://docs.rs/rayon/1.0/rayon
72 pub mod rayon {
73 pub use crate::external_trait_impls::rayon::raw::*;
74 }
75}
76#[cfg(not(feature = "raw"))]
77mod raw;
78
79mod external_trait_impls;
80mod map;
81#[cfg(feature = "rustc-internal-api")]
82mod rustc_entry;
83mod scopeguard;
84mod set;
85mod table;
86
87pub mod hash_map {
88 //! A hash map implemented with quadratic probing and SIMD lookup.
89 pub use crate::map::*;
90
91 #[cfg(feature = "rustc-internal-api")]
92 pub use crate::rustc_entry::*;
93
94 #[cfg(feature = "rayon")]
95 /// [rayon]-based parallel iterator types for hash maps.
96 /// You will rarely need to interact with it directly unless you have need
97 /// to name one of the iterator types.
98 ///
99 /// [rayon]: https://docs.rs/rayon/1.0/rayon
100 pub mod rayon {
101 pub use crate::external_trait_impls::rayon::map::*;
102 }
103}
104pub mod hash_set {
105 //! A hash set implemented as a `HashMap` where the value is `()`.
106 pub use crate::set::*;
107
108 #[cfg(feature = "rayon")]
109 /// [rayon]-based parallel iterator types for hash sets.
110 /// You will rarely need to interact with it directly unless you have need
111 /// to name one of the iterator types.
112 ///
113 /// [rayon]: https://docs.rs/rayon/1.0/rayon
114 pub mod rayon {
115 pub use crate::external_trait_impls::rayon::set::*;
116 }
117}
118pub mod hash_table {
119 //! A hash table implemented with quadratic probing and SIMD lookup.
120 pub use crate::table::*;
121
122 #[cfg(feature = "rayon")]
123 /// [rayon]-based parallel iterator types for hash tables.
124 /// You will rarely need to interact with it directly unless you have need
125 /// to name one of the iterator types.
126 ///
127 /// [rayon]: https://docs.rs/rayon/1.0/rayon
128 pub mod rayon {
129 pub use crate::external_trait_impls::rayon::table::*;
130 }
131}
132
133pub use crate::map::HashMap;
134pub use crate::set::HashSet;
135pub use crate::table::HashTable;
136
137#[cfg(feature = "equivalent")]
138pub use equivalent::Equivalent;
139
140// This is only used as a fallback when building as part of `std`.
141#[cfg(not(feature = "equivalent"))]
142/// Key equivalence trait.
143///
144/// This trait defines the function used to compare the input value with the
145/// map keys (or set values) during a lookup operation such as [`HashMap::get`]
146/// or [`HashSet::contains`].
147/// It is provided with a blanket implementation based on the
148/// [`Borrow`](core::borrow::Borrow) trait.
149///
150/// # Correctness
151///
152/// Equivalent values must hash to the same value.
153pub trait Equivalent<K: ?Sized> {
154 /// Checks if this value is equivalent to the given key.
155 ///
156 /// Returns `true` if both values are equivalent, and `false` otherwise.
157 ///
158 /// # Correctness
159 ///
160 /// When this function returns `true`, both `self` and `key` must hash to
161 /// the same value.
162 fn equivalent(&self, key: &K) -> bool;
163}
164
165#[cfg(not(feature = "equivalent"))]
166impl<Q: ?Sized, K: ?Sized> Equivalent<K> for Q
167where
168 Q: Eq,
169 K: core::borrow::Borrow<Q>,
170{
171 fn equivalent(&self, key: &K) -> bool {
172 self == key.borrow()
173 }
174}
175
176/// The error type for `try_reserve` methods.
177#[derive(Clone, PartialEq, Eq, Debug)]
178pub enum TryReserveError {
179 /// Error due to the computed capacity exceeding the collection's maximum
180 /// (usually `isize::MAX` bytes).
181 CapacityOverflow,
182
183 /// The memory allocator returned an error
184 AllocError {
185 /// The layout of the allocation request that failed.
186 layout: alloc::alloc::Layout,
187 },
188}