1 const GF2_DIM: usize = 32;
2
gf2_matrix_times(mat: &[u32; GF2_DIM], mut vec: u32) -> u323 fn gf2_matrix_times(mat: &[u32; GF2_DIM], mut vec: u32) -> u32 {
4 let mut sum = 0;
5 let mut idx = 0;
6 while vec > 0 {
7 if vec & 1 == 1 {
8 sum ^= mat[idx];
9 }
10 vec >>= 1;
11 idx += 1;
12 }
13 return sum;
14 }
15
gf2_matrix_square(square: &mut [u32; GF2_DIM], mat: &[u32; GF2_DIM])16 fn gf2_matrix_square(square: &mut [u32; GF2_DIM], mat: &[u32; GF2_DIM]) {
17 for n in 0..GF2_DIM {
18 square[n] = gf2_matrix_times(mat, mat[n]);
19 }
20 }
21
combine(mut crc1: u32, crc2: u32, mut len2: u64) -> u3222 pub(crate) fn combine(mut crc1: u32, crc2: u32, mut len2: u64) -> u32 {
23 let mut row: u32;
24 let mut even = [0u32; GF2_DIM]; /* even-power-of-two zeros operator */
25 let mut odd = [0u32; GF2_DIM]; /* odd-power-of-two zeros operator */
26
27 /* degenerate case (also disallow negative lengths) */
28 if len2 <= 0 {
29 return crc1;
30 }
31
32 /* put operator for one zero bit in odd */
33 odd[0] = 0xedb88320; /* CRC-32 polynomial */
34 row = 1;
35 for n in 1..GF2_DIM {
36 odd[n] = row;
37 row <<= 1;
38 }
39
40 /* put operator for two zero bits in even */
41 gf2_matrix_square(&mut even, &odd);
42
43 /* put operator for four zero bits in odd */
44 gf2_matrix_square(&mut odd, &even);
45
46 /* apply len2 zeros to crc1 (first square will put the operator for one
47 zero byte, eight zero bits, in even) */
48 loop {
49 /* apply zeros operator for this bit of len2 */
50 gf2_matrix_square(&mut even, &odd);
51 if len2 & 1 == 1 {
52 crc1 = gf2_matrix_times(&even, crc1);
53 }
54 len2 >>= 1;
55
56 /* if no more bits set, then done */
57 if len2 == 0 {
58 break;
59 }
60
61 /* another iteration of the loop with odd and even swapped */
62 gf2_matrix_square(&mut odd, &even);
63 if len2 & 1 == 1 {
64 crc1 = gf2_matrix_times(&odd, crc1);
65 }
66 len2 >>= 1;
67
68 /* if no more bits set, then done */
69 if len2 == 0 {
70 break;
71 }
72 }
73
74 /* return combined crc */
75 crc1 ^= crc2;
76 return crc1;
77 }
78