1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102

use locspan::{Stripped, StrippedHash};
use std::collections::{hash_map::DefaultHasher, HashMap};
use std::hash::{Hash, Hasher};

/// Hash a [`HashSet`].
///
/// The standard library does not provide (yet) a `Hash` implementation
/// for the [`HashSet`] type. This can be used instead.
///
/// Note that this function not particularly strong and does
/// not protect against DoS attacks.
pub fn hash_set<S: IntoIterator, H: Hasher>(set: S, hasher: &mut H)
where
	S::Item: Hash,
{
	// See: https://github.com/rust-lang/rust/pull/48366
	// Elements must be combined with a associative and commutative operation •.
	// (u64, •, 0) must form a commutative monoid.
	// This is satisfied by • = u64::wrapping_add.
	let mut hash = 0;
	for item in set {
		let mut h = DefaultHasher::new();
		item.hash(&mut h);
		hash = u64::wrapping_add(hash, h.finish());
	}

	hasher.write_u64(hash);
}

pub fn hash_set_stripped<S: IntoIterator, H: Hasher>(set: S, hasher: &mut H)
where
	S::Item: StrippedHash,
{
	// See: https://github.com/rust-lang/rust/pull/48366
	// Elements must be combined with a associative and commutative operation •.
	// (u64, •, 0) must form a commutative monoid.
	// This is satisfied by • = u64::wrapping_add.
	let mut hash = 0;
	for item in set {
		let mut h = DefaultHasher::new();
		item.stripped_hash(&mut h);
		hash = u64::wrapping_add(hash, h.finish());
	}

	hasher.write_u64(hash);
}

/// Hash an optional [`HashSet`].
pub fn hash_set_opt<S: IntoIterator, H: Hasher>(set_opt: Option<S>, hasher: &mut H)
where
	S::Item: Hash,
{
	if let Some(set) = set_opt {
		hash_set(set, hasher)
	}
}

pub fn hash_set_stripped_opt<S: IntoIterator, H: Hasher>(set_opt: Option<S>, hasher: &mut H)
where
	S::Item: StrippedHash,
{
	if let Some(set) = set_opt {
		hash_set_stripped(set, hasher)
	}
}

/// Hash a [`HashMap`].
///
/// The standard library does not provide (yet) a `Hash` implementation
/// for the [`HashMap`] type. This can be used instead.
///
/// Note that this function not particularly strong and does
/// not protect against DoS attacks.
pub fn hash_map<K: Hash, V: Hash, H: Hasher>(map: &HashMap<K, V>, hasher: &mut H) {
	// See: https://github.com/rust-lang/rust/pull/48366
	// Elements must be combined with a associative and commutative operation •.
	// (u64, •, 0) must form a commutative monoid.
	// This is satisfied by • = u64::wrapping_add.
	let mut hash = 0;
	for entry in map {
		let mut h = DefaultHasher::new();
		entry.hash(&mut h);
		hash = u64::wrapping_add(hash, h.finish());
	}

	hasher.write_u64(hash);
}

pub fn hash_map_stripped<K: Hash, V: StrippedHash, H: Hasher>(map: &HashMap<K, V>, hasher: &mut H) {
	// See: https://github.com/rust-lang/rust/pull/48366
	// Elements must be combined with a associative and commutative operation •.
	// (u64, •, 0) must form a commutative monoid.
	// This is satisfied by • = u64::wrapping_add.
	let mut hash = 0;
	for (k, v) in map {
		let mut h = DefaultHasher::new();
		(k, Stripped(v)).hash(&mut h);
		hash = u64::wrapping_add(hash, h.finish());
	}

	hasher.write_u64(hash);
}