simd_adler32/imp/
scalar.rs

1const MOD: u32 = 65521;
2const NMAX: usize = 5552;
3
4pub fn update(a: u16, b: u16, data: &[u8]) -> (u16, u16) {
5  let mut a = a as u32;
6  let mut b = b as u32;
7
8  let chunks = data.chunks_exact(NMAX);
9  let remainder = chunks.remainder();
10
11  for chunk in chunks {
12    for byte in chunk {
13      a = a.wrapping_add(*byte as _);
14      b = b.wrapping_add(a);
15    }
16
17    a %= MOD;
18    b %= MOD;
19  }
20
21  for byte in remainder {
22    a = a.wrapping_add(*byte as _);
23    b = b.wrapping_add(a);
24  }
25
26  a %= MOD;
27  b %= MOD;
28
29  (a as u16, b as u16)
30}
31
32#[cfg(test)]
33mod tests {
34  #[test]
35  fn zeroes_short() {
36    assert_eq!(adler32(&[]), 1);
37    assert_eq!(adler32(&[0]), 1 | 1 << 16);
38    assert_eq!(adler32(&[0, 0]), 1 | 2 << 16);
39    assert_eq!(adler32(&[0; 100]), 0x00640001);
40    assert_eq!(adler32(&[0; 1024]), 0x04000001);
41  }
42
43  #[test]
44  #[cfg_attr(miri, ignore)]
45  fn zeroes_long() {
46    assert_eq!(adler32(&[0; 1024 * 1024]), 0x00f00001);
47  }
48
49  #[test]
50  fn ones_short() {
51    assert_eq!(adler32(&[0xff; 1024]), 0x79a6fc2e);
52  }
53
54  #[test]
55  #[cfg_attr(miri, ignore)]
56  fn ones_long() {
57    assert_eq!(adler32(&[0xff; 1024 * 1024]), 0x8e88ef11);
58  }
59
60  #[test]
61  fn mixed_short() {
62    assert_eq!(adler32(&[1]), 2 | 2 << 16);
63    assert_eq!(adler32(&[40]), 41 | 41 << 16);
64  }
65
66  #[test]
67  #[cfg_attr(miri, ignore)]
68  fn mixed_long() {
69    assert_eq!(adler32(&[0xA5; 1024 * 1024]), 0xd5009ab1);
70  }
71
72  /// Example calculation from https://en.wikipedia.org/wiki/Adler-32.
73  #[test]
74  fn wiki() {
75    assert_eq!(adler32(b"Wikipedia"), 0x11E60398);
76  }
77
78  fn adler32(data: &[u8]) -> u32 {
79    let (a, b) = super::update(1, 0, data);
80
81    u32::from(b) << 16 | u32::from(a)
82  }
83}
simd_adler32/imp/scalar.rs

simd_adler32/imp/
scalar.rs
