hashbrown/
hasher.rs

1#[cfg(feature = "default-hasher")]
2use {
3    core::hash::{BuildHasher, Hasher},
4    foldhash::fast::RandomState,
5};
6
7/// Default hash builder for the `S` type parameter of
8/// [`HashMap`](crate::HashMap) and [`HashSet`](crate::HashSet).
9///
10/// This only implements `BuildHasher` when the "default-hasher" crate feature
11/// is enabled; otherwise it just serves as a placeholder, and a custom `S` type
12/// must be used to have a fully functional `HashMap` or `HashSet`.
13#[derive(Clone, Debug, Default)]
14pub struct DefaultHashBuilder {
15    #[cfg(feature = "default-hasher")]
16    inner: RandomState,
17}
18
19#[cfg(feature = "default-hasher")]
20impl BuildHasher for DefaultHashBuilder {
21    type Hasher = DefaultHasher;
22
23    #[inline(always)]
24    fn build_hasher(&self) -> Self::Hasher {
25        DefaultHasher {
26            inner: self.inner.build_hasher(),
27        }
28    }
29}
30
31/// Default hasher for [`HashMap`](crate::HashMap) and [`HashSet`](crate::HashSet).
32#[cfg(feature = "default-hasher")]
33#[derive(Clone)]
34pub struct DefaultHasher {
35    inner: <RandomState as BuildHasher>::Hasher,
36}
37
38#[cfg(feature = "default-hasher")]
39macro_rules! forward_writes {
40    ($( $write:ident ( $ty:ty ) , )*) => {$(
41        #[inline(always)]
42        fn $write(&mut self, arg: $ty) {
43            self.inner.$write(arg);
44        }
45    )*}
46}
47
48#[cfg(feature = "default-hasher")]
49impl Hasher for DefaultHasher {
50    forward_writes! {
51        write(&[u8]),
52        write_u8(u8),
53        write_u16(u16),
54        write_u32(u32),
55        write_u64(u64),
56        write_u128(u128),
57        write_usize(usize),
58        write_i8(i8),
59        write_i16(i16),
60        write_i32(i32),
61        write_i64(i64),
62        write_i128(i128),
63        write_isize(isize),
64    }
65
66    // feature(hasher_prefixfree_extras)
67    #[cfg(feature = "nightly")]
68    forward_writes! {
69        write_length_prefix(usize),
70        write_str(&str),
71    }
72
73    #[inline(always)]
74    fn finish(&self) -> u64 {
75        self.inner.finish()
76    }
77}
hashbrown/hasher.rs

hashbrown/
hasher.rs
