1 | use table::CRC32_TABLE; |
2 | |
3 | #[derive (Clone)] |
4 | pub struct State { |
5 | state: u32, |
6 | } |
7 | |
8 | impl 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 | |
30 | pub(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 | |
61 | pub(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)] |
72 | mod 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 | |