1use table::CRC32_TABLE;
2
3#[derive(Clone)]
4pub struct State {
5 state: u32,
6}
7
8impl State {
9 pub fn new(state: u32) -> Self {
10 State { state }
11 }
12
13 pub fn update(&mut self, buf: &[u8]) {
14 self.state = update_fast_16(self.state, buf);
15 }
16
17 pub fn finalize(self) -> u32 {
18 self.state
19 }
20
21 pub fn reset(&mut self) {
22 self.state = 0;
23 }
24
25 pub fn combine(&mut self, other: u32, amount: u64) {
26 self.state = ::combine::combine(self.state, crc2:other, len2:amount);
27 }
28}
29
30pub(crate) fn update_fast_16(prev: u32, mut buf: &[u8]) -> u32 {
31 const UNROLL: usize = 4;
32 const BYTES_AT_ONCE: usize = 16 * UNROLL;
33
34 let mut crc = !prev;
35
36 while buf.len() >= BYTES_AT_ONCE {
37 for _ in 0..UNROLL {
38 crc = CRC32_TABLE[0x0][buf[0xf] as usize]
39 ^ CRC32_TABLE[0x1][buf[0xe] as usize]
40 ^ CRC32_TABLE[0x2][buf[0xd] as usize]
41 ^ CRC32_TABLE[0x3][buf[0xc] as usize]
42 ^ CRC32_TABLE[0x4][buf[0xb] as usize]
43 ^ CRC32_TABLE[0x5][buf[0xa] as usize]
44 ^ CRC32_TABLE[0x6][buf[0x9] as usize]
45 ^ CRC32_TABLE[0x7][buf[0x8] as usize]
46 ^ CRC32_TABLE[0x8][buf[0x7] as usize]
47 ^ CRC32_TABLE[0x9][buf[0x6] as usize]
48 ^ CRC32_TABLE[0xa][buf[0x5] as usize]
49 ^ CRC32_TABLE[0xb][buf[0x4] as usize]
50 ^ CRC32_TABLE[0xc][buf[0x3] as usize ^ ((crc >> 0x18) & 0xFF) as usize]
51 ^ CRC32_TABLE[0xd][buf[0x2] as usize ^ ((crc >> 0x10) & 0xFF) as usize]
52 ^ CRC32_TABLE[0xe][buf[0x1] as usize ^ ((crc >> 0x08) & 0xFF) as usize]
53 ^ CRC32_TABLE[0xf][buf[0x0] as usize ^ ((crc >> 0x00) & 0xFF) as usize];
54 buf = &buf[16..];
55 }
56 }
57
58 update_slow(!crc, buf)
59}
60
61pub(crate) fn update_slow(prev: u32, buf: &[u8]) -> u32 {
62 let mut crc: u32 = !prev;
63
64 for &byte: u8 in buf.iter() {
65 crc = CRC32_TABLE[0][((crc as u8) ^ byte) as usize] ^ (crc >> 8);
66 }
67
68 !crc
69}
70
71#[cfg(test)]
72mod test {
73 #[test]
74 fn slow() {
75 assert_eq!(super::update_slow(0, b""), 0);
76
77 // test vectors from the iPXE project (input and output are bitwise negated)
78 assert_eq!(super::update_slow(!0x12345678, b""), !0x12345678);
79 assert_eq!(super::update_slow(!0xffffffff, b"hello world"), !0xf2b5ee7a);
80 assert_eq!(super::update_slow(!0xffffffff, b"hello"), !0xc9ef5979);
81 assert_eq!(super::update_slow(!0xc9ef5979, b" world"), !0xf2b5ee7a);
82
83 // Some vectors found on Rosetta code
84 assert_eq!(super::update_slow(0, b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"), 0x190A55AD);
85 assert_eq!(super::update_slow(0, b"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"), 0xFF6CAB0B);
86 assert_eq!(super::update_slow(0, b"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F"), 0x91267E8A);
87 }
88
89 quickcheck! {
90 fn fast_16_is_the_same_as_slow(crc: u32, bytes: Vec<u8>) -> bool {
91 super::update_fast_16(crc, &bytes) == super::update_slow(crc, &bytes)
92 }
93 }
94}
95