phf_shared/
hasher.rs

1use core::hash::Hasher;
2use siphasher::sip128::{Hash128, Hasher128};
3
4pub struct PortableSipHasher<H> {
5    inner: H,
6}
7
8impl<H> PortableSipHasher<H> {
9    pub fn new(inner: H) -> Self {
10        Self { inner }
11    }
12}
13
14impl<H: Hasher> Hasher for PortableSipHasher<H> {
15    fn finish(&self) -> u64 {
16        self.inner.finish()
17    }
18
19    fn write(&mut self, bytes: &[u8]) {
20        self.inner.write(bytes)
21    }
22
23    fn write_u8(&mut self, i: u8) {
24        self.inner.write_u8(i)
25    }
26
27    // `SipHasher` invokes `to_le` on integers before encoding them, treating them as byte arrays
28    // rather than values, which is not the right interpretation for us; fix that by flipping
29    // endianness twice.
30    fn write_u16(&mut self, i: u16) {
31        self.inner.write_u16(i.to_le());
32    }
33    fn write_u32(&mut self, i: u32) {
34        self.inner.write_u32(i.to_le());
35    }
36    fn write_u64(&mut self, i: u64) {
37        self.inner.write_u64(i.to_le());
38    }
39    fn write_u128(&mut self, i: u128) {
40        self.inner.write_u128(i.to_le());
41    }
42
43    fn write_usize(&mut self, i: usize) {
44        self.inner.write_u64((i as u64).to_le());
45    }
46    // The default `write_isize` implementation casts to `usize` first, so we end up with
47    // `i as usize as u64`, which is different on 32-bit and 64-bit architectures:
48    //
49    // 32-bit: `-1` -> `2^32 - 1` -> `2^32 - 1`
50    // 64-bit: `-1` -> `2^64 - 1` -> `2^64 - 1`
51    fn write_isize(&mut self, i: isize) {
52        self.inner.write_u64((i as u64).to_le());
53    }
54
55    // Fixed-size signed integers correctly forward to unsigned implementations.
56}
57
58impl<H: Hasher128> Hasher128 for PortableSipHasher<H> {
59    fn finish128(&self) -> Hash128 {
60        self.inner.finish128()
61    }
62}
phf_shared/hasher.rs

phf_shared/
hasher.rs
