dryoc/
utils.rs

1/// Increments `bytes` in constant time, representing a large little-endian
2/// integer; equivalent to `sodium_increment`.
3#[inline]
4pub fn increment_bytes(bytes: &mut [u8]) {
5    let mut carry: u16 = 1;
6    for b in bytes {
7        carry += *b as u16;
8        *b = (carry & 0xff) as u8;
9        carry >>= 8;
10    }
11}
12
13/// Convenience wrapper for [`increment_bytes`]. Functionally equivalent to
14/// `sodium_increment`.
15pub fn sodium_increment(bytes: &mut [u8]) {
16    increment_bytes(bytes)
17}
18
19#[inline]
20pub(crate) fn xor_buf(out: &mut [u8], in_: &[u8]) {
21    let len = std::cmp::min(out.len(), in_.len());
22    for i in 0..len {
23        out[i] ^= in_[i];
24    }
25}
26
27#[inline]
28pub(crate) fn load_u64_le(bytes: &[u8]) -> u64 {
29    (bytes[0] as u64)
30        | ((bytes[1] as u64) << 8)
31        | ((bytes[2] as u64) << 16)
32        | ((bytes[3] as u64) << 24)
33        | ((bytes[4] as u64) << 32)
34        | ((bytes[5] as u64) << 40)
35        | ((bytes[6] as u64) << 48)
36        | ((bytes[7] as u64) << 56)
37}
38
39#[inline]
40pub(crate) fn load_u32_le(bytes: &[u8]) -> u32 {
41    (bytes[0] as u32)
42        | ((bytes[1] as u32) << 8)
43        | ((bytes[2] as u32) << 16)
44        | ((bytes[3] as u32) << 24)
45}
46
47#[inline]
48#[cfg_attr(all(feature = "simd_backend", feature = "nightly"), allow(dead_code))]
49pub(crate) fn rotr64(x: u64, b: u32) -> u64 {
50    x.rotate_right(b)
51}
52
53#[inline]
54pub(crate) fn pad16(n: usize) -> usize {
55    (0x10 - (n % 16)) & 0xf
56}
57
58#[cfg(test)]
59mod tests {
60    use super::*;
61
62    #[test]
63    fn test_increment_bytes() {
64        let mut b = [0];
65
66        increment_bytes(&mut b);
67        assert_eq!(b, [1]);
68        increment_bytes(&mut b);
69        assert_eq!(b, [2]);
70
71        let mut b = [0xff];
72
73        increment_bytes(&mut b);
74        assert_eq!(b, [0]);
75        increment_bytes(&mut b);
76        assert_eq!(b, [1]);
77
78        let mut b = [0xff, 0];
79
80        increment_bytes(&mut b);
81        assert_eq!(b, [0, 1]);
82        increment_bytes(&mut b);
83        assert_eq!(b, [1, 1]);
84        increment_bytes(&mut b);
85        assert_eq!(b, [2, 1]);
86    }
87
88    #[test]
89    fn test_xor_buf() {
90        let mut a = [0];
91        let b = [0];
92
93        xor_buf(&mut a, &b);
94        assert_eq!([0], a);
95
96        let mut a = [1];
97        let b = [0];
98
99        xor_buf(&mut a, &b);
100        assert_eq!([1], a);
101
102        let mut a = [1, 1, 1];
103        let b = [0];
104
105        xor_buf(&mut a, &b);
106        assert_eq!([1, 1, 1], a);
107
108        let mut a = [1, 1, 1];
109        let b = [0];
110
111        xor_buf(&mut a, &b);
112        assert_eq!([1, 1, 1], a);
113
114        let mut a = [1, 1, 1];
115        let b = [0, 1, 1];
116
117        xor_buf(&mut a, &b);
118        assert_eq!([1, 0, 0], a);
119    }
120
121    #[test]
122    fn test_pad16() {
123        assert_eq!(pad16(0), 0);
124        assert_eq!(pad16(1), 15);
125        assert_eq!(pad16(2), 14);
126        assert_eq!(pad16(15), 1);
127        assert_eq!(pad16(16), 0);
128        assert_eq!(pad16(17), 15);
129        assert_eq!(pad16(32), 0);
130        assert_eq!(pad16(33), 15);
131    }
132
133    #[cfg(dryoc_native_tests)]
134    mod native_tests {
135        use super::*;
136
137        #[test]
138        fn test_sodium_increment() {
139            use libsodium_sys::sodium_increment as so_sodium_increment;
140            use rand::TryRng;
141            use rand::rngs::SysRng;
142
143            use crate::rng::copy_randombytes;
144
145            for _ in 0..20 {
146                let rand_usize = (SysRng.try_next_u32().unwrap() % 1000) as usize;
147                let mut data = vec![0u8; rand_usize];
148                copy_randombytes(&mut data);
149
150                let mut data_copy = data.clone();
151
152                sodium_increment(&mut data);
153
154                unsafe { so_sodium_increment(data_copy.as_mut_ptr(), data_copy.len()) };
155
156                assert_eq!(data, data_copy);
157            }
158        }
159    }
160}
dryoc/utils.rs

dryoc/
utils.rs
