/rust/registry/src/index.crates.io-1949cf8c6b5b557f/foldhash-0.2.0/src/quality.rs

Source
//! The foldhash implementation optimized for quality.

use core::hash::{BuildHasher, Hasher};

use crate::seed::SharedSeed;

use crate::{fast, folded_multiply, ARBITRARY0, ARBITRARY4};

/// A [`Hasher`] instance implementing foldhash, optimized for quality.
///
/// While you can create one directly with [`FoldHasher::with_seed`], you
/// most likely want to use [`RandomState`], [`SeedableRandomState`] or
/// [`FixedState`] to create [`FoldHasher`]s.
#[derive(Clone)]
pub struct FoldHasher<'a> {
    pub(crate) inner: fast::FoldHasher<'a>,
}

impl<'a> FoldHasher<'a> {
    /// Initializes this [`FoldHasher`] with the given per-hasher seed and
    /// [`SharedSeed`].
    #[inline(always)]
    pub const fn with_seed(per_hasher_seed: u64, shared_seed: &'a SharedSeed) -> FoldHasher<'a> {
        FoldHasher {
            inner: fast::FoldHasher::with_seed(per_hasher_seed, shared_seed),
        }
    }
}

impl<'a> Hasher for FoldHasher<'a> {
    #[inline(always)]
    fn write(&mut self, bytes: &[u8]) {
        self.inner.write(bytes);
    }

    #[inline(always)]
    fn write_u8(&mut self, i: u8) {
        self.inner.write_u8(i);
    }

    #[inline(always)]
    fn write_u16(&mut self, i: u16) {
        self.inner.write_u16(i);
    }

    #[inline(always)]
    fn write_u32(&mut self, i: u32) {
        self.inner.write_u32(i);
    }

    #[inline(always)]
    fn write_u64(&mut self, i: u64) {
        self.inner.write_u64(i);
    }

    #[inline(always)]
    fn write_u128(&mut self, i: u128) {
        self.inner.write_u128(i);
    }

    #[inline(always)]
    fn write_usize(&mut self, i: usize) {
        self.inner.write_usize(i);
    }

    #[cfg(feature = "nightly")]
    #[inline(always)]
    fn write_str(&mut self, s: &str) {
        self.inner.write_str(s);
    }

    #[inline(always)]
    fn finish(&self) -> u64 {
        folded_multiply(self.inner.finish(), ARBITRARY0)
    }
}

/// A [`BuildHasher`] for [`quality::FoldHasher`](FoldHasher) that is randomly initialized.
#[derive(Clone, Default, Debug)]
pub struct RandomState {
    inner: fast::RandomState,
}

impl BuildHasher for RandomState {
    type Hasher = FoldHasher<'static>;

    #[inline(always)]
    fn build_hasher(&self) -> FoldHasher<'static> {
        FoldHasher {
            inner: self.inner.build_hasher(),
        }
    }
}

/// A [`BuildHasher`] for [`quality::FoldHasher`](FoldHasher) that is randomly
/// initialized by default, but can also be initialized with a specific seed.
///
/// This can be useful for e.g. testing, but the downside is that this type
/// has a size of 16 bytes rather than the 8 bytes [`RandomState`] is.
#[derive(Clone, Default, Debug)]
pub struct SeedableRandomState {
    inner: fast::SeedableRandomState,
}

impl SeedableRandomState {
    /// Generates a random [`SeedableRandomState`], similar to [`RandomState`].
    #[inline(always)]
    pub fn random() -> Self {
        Self {
            inner: fast::SeedableRandomState::random(),
        }
    }

    /// Generates a fixed [`SeedableRandomState`], similar to [`FixedState`].
    #[inline(always)]
    pub fn fixed() -> Self {
        Self {
            inner: fast::SeedableRandomState::fixed(),
        }
    }

    /// Generates a [`SeedableRandomState`] with the given per-hasher seed
    /// and [`SharedSeed`].
    #[inline(always)]
    pub fn with_seed(per_hasher_seed: u64, shared_seed: &'static SharedSeed) -> Self {
        Self {
            // We do an additional folded multiply with the seed here for
            // the quality hash to ensure better independence between seed
            // and hash.
            inner: fast::SeedableRandomState::with_seed(
                folded_multiply(per_hasher_seed, ARBITRARY4),
                shared_seed,
            ),
        }
    }
}

impl BuildHasher for SeedableRandomState {
    type Hasher = FoldHasher<'static>;

    #[inline(always)]
    fn build_hasher(&self) -> FoldHasher<'static> {
        FoldHasher {
            inner: self.inner.build_hasher(),
        }
    }
}

/// A [`BuildHasher`] for [`quality::FoldHasher`](FoldHasher) that always has the same fixed seed.
///
/// Not recommended unless you absolutely need determinism.
#[derive(Clone, Default, Debug)]
pub struct FixedState {
    inner: fast::FixedState,
}

impl FixedState {
    /// Creates a [`FixedState`] with the given per-hasher seed.
    #[inline(always)]
    pub const fn with_seed(per_hasher_seed: u64) -> Self {
        Self {
            // We do an additional folded multiply with the seed here for
            // the quality hash to ensure better independence between seed
            // and hash. If the seed is zero the folded multiply is zero,
            // preserving with_seed(0) == default().
            inner: fast::FixedState::with_seed(folded_multiply(per_hasher_seed, ARBITRARY4)),
        }
    }
}

impl BuildHasher for FixedState {
    type Hasher = FoldHasher<'static>;

    #[inline(always)]
    fn build_hasher(&self) -> FoldHasher<'static> {
        FoldHasher {
            inner: self.inner.build_hasher(),
        }
    }
}

Line	Count	Source
1		//! The foldhash implementation optimized for quality.
2
3		use core::hash::{BuildHasher, Hasher};
4
5		use crate::seed::SharedSeed;
6
7		use crate::{fast, folded_multiply, ARBITRARY0, ARBITRARY4};
8
9		/// A [`Hasher`] instance implementing foldhash, optimized for quality.
10		///
11		/// While you can create one directly with [`FoldHasher::with_seed`], you
12		/// most likely want to use [`RandomState`], [`SeedableRandomState`] or
13		/// [`FixedState`] to create [`FoldHasher`]s.
14		#[derive(Clone)]
15		pub struct FoldHasher<'a> {
16		pub(crate) inner: fast::FoldHasher<'a>,
17		}
18
19		impl<'a> FoldHasher<'a> {
20		/// Initializes this [`FoldHasher`] with the given per-hasher seed and
21		/// [`SharedSeed`].
22		#[inline(always)]
23	0	pub const fn with_seed(per_hasher_seed: u64, shared_seed: &'a SharedSeed) -> FoldHasher<'a> {
24	0	FoldHasher {
25	0	inner: fast::FoldHasher::with_seed(per_hasher_seed, shared_seed),
26	0	}
27	0	}
28		}
29
30		impl<'a> Hasher for FoldHasher<'a> {
31		#[inline(always)]
32	0	fn write(&mut self, bytes: &[u8]) {
33	0	self.inner.write(bytes);
34	0	}
35
36		#[inline(always)]
37	0	fn write_u8(&mut self, i: u8) {
38	0	self.inner.write_u8(i);
39	0	}
40
41		#[inline(always)]
42	0	fn write_u16(&mut self, i: u16) {
43	0	self.inner.write_u16(i);
44	0	}
45
46		#[inline(always)]
47	0	fn write_u32(&mut self, i: u32) {
48	0	self.inner.write_u32(i);
49	0	}
50
51		#[inline(always)]
52	0	fn write_u64(&mut self, i: u64) {
53	0	self.inner.write_u64(i);
54	0	}
55
56		#[inline(always)]
57	0	fn write_u128(&mut self, i: u128) {
58	0	self.inner.write_u128(i);
59	0	}
60
61		#[inline(always)]
62	0	fn write_usize(&mut self, i: usize) {
63	0	self.inner.write_usize(i);
64	0	}
65
66		#[cfg(feature = "nightly")]
67		#[inline(always)]
68		fn write_str(&mut self, s: &str) {
69		self.inner.write_str(s);
70		}
71
72		#[inline(always)]
73	0	fn finish(&self) -> u64 {
74	0	folded_multiply(self.inner.finish(), ARBITRARY0)
75	0	}
76		}
77
78		/// A [`BuildHasher`] for [`quality::FoldHasher`](FoldHasher) that is randomly initialized.
79		#[derive(Clone, Default, Debug)]
80		pub struct RandomState {
81		inner: fast::RandomState,
82		}
83
84		impl BuildHasher for RandomState {
85		type Hasher = FoldHasher<'static>;
86
87		#[inline(always)]
88	0	fn build_hasher(&self) -> FoldHasher<'static> {
89	0	FoldHasher {
90	0	inner: self.inner.build_hasher(),
91	0	}
92	0	}
93		}
94
95		/// A [`BuildHasher`] for [`quality::FoldHasher`](FoldHasher) that is randomly
96		/// initialized by default, but can also be initialized with a specific seed.
97		///
98		/// This can be useful for e.g. testing, but the downside is that this type
99		/// has a size of 16 bytes rather than the 8 bytes [`RandomState`] is.
100		#[derive(Clone, Default, Debug)]
101		pub struct SeedableRandomState {
102		inner: fast::SeedableRandomState,
103		}
104
105		impl SeedableRandomState {
106		/// Generates a random [`SeedableRandomState`], similar to [`RandomState`].
107		#[inline(always)]
108	0	pub fn random() -> Self {
109	0	Self {
110	0	inner: fast::SeedableRandomState::random(),
111	0	}
112	0	}
113
114		/// Generates a fixed [`SeedableRandomState`], similar to [`FixedState`].
115		#[inline(always)]
116	0	pub fn fixed() -> Self {
117	0	Self {
118	0	inner: fast::SeedableRandomState::fixed(),
119	0	}
120	0	}
121
122		/// Generates a [`SeedableRandomState`] with the given per-hasher seed
123		/// and [`SharedSeed`].
124		#[inline(always)]
125	0	pub fn with_seed(per_hasher_seed: u64, shared_seed: &'static SharedSeed) -> Self {
126	0	Self {
127	0	// We do an additional folded multiply with the seed here for
128	0	// the quality hash to ensure better independence between seed
129	0	// and hash.
130	0	inner: fast::SeedableRandomState::with_seed(
131	0	folded_multiply(per_hasher_seed, ARBITRARY4),
132	0	shared_seed,
133	0	),
134	0	}
135	0	}
136		}
137
138		impl BuildHasher for SeedableRandomState {
139		type Hasher = FoldHasher<'static>;
140
141		#[inline(always)]
142	0	fn build_hasher(&self) -> FoldHasher<'static> {
143	0	FoldHasher {
144	0	inner: self.inner.build_hasher(),
145	0	}
146	0	}
147		}
148
149		/// A [`BuildHasher`] for [`quality::FoldHasher`](FoldHasher) that always has the same fixed seed.
150		///
151		/// Not recommended unless you absolutely need determinism.
152		#[derive(Clone, Default, Debug)]
153		pub struct FixedState {
154		inner: fast::FixedState,
155		}
156
157		impl FixedState {
158		/// Creates a [`FixedState`] with the given per-hasher seed.
159		#[inline(always)]
160	0	pub const fn with_seed(per_hasher_seed: u64) -> Self {
161	0	Self {
162	0	// We do an additional folded multiply with the seed here for
163	0	// the quality hash to ensure better independence between seed
164	0	// and hash. If the seed is zero the folded multiply is zero,
165	0	// preserving with_seed(0) == default().
166	0	inner: fast::FixedState::with_seed(folded_multiply(per_hasher_seed, ARBITRARY4)),
167	0	}
168	0	}
169		}
170
171		impl BuildHasher for FixedState {
172		type Hasher = FoldHasher<'static>;
173
174		#[inline(always)]
175	0	fn build_hasher(&self) -> FoldHasher<'static> {
176	0	FoldHasher {
177	0	inner: self.inner.build_hasher(),
178	0	}
179	0	}
180		}

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Created: 2026-09-19 07:25