network_types/
bitfield.rs

1//! A Rust bitfield implementation, copied from
2//! [bindgen](https://github.com/rust-lang/rust-bindgen/blob/master/bindgen/codegen/bitfield_unit.rs)
3//! which is licensed under the
4//! [BSD 3-Clause license](https://github.com/rust-lang/rust-bindgen/blob/master/LICENSE).
5
6#[repr(C)]
7#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
8#[cfg_attr(feature = "wincode", derive(wincode::SchemaRead, wincode::SchemaWrite))]
9#[cfg_attr(feature = "wincode", wincode(assert_zero_copy))]
10pub struct BitfieldU16 {
11    storage: [u8; 2],
12}
13
14impl BitfieldU16 {
15    #[inline]
16    pub const fn new(storage: [u8; 2]) -> Self {
17        Self { storage }
18    }
19
20    #[inline]
21    pub fn get_bit(&self, index: usize) -> bool {
22        debug_assert!(index / 8 < self.storage.as_ref().len());
23
24        let byte_index = index / 8;
25        let byte = self.storage.as_ref()[byte_index];
26
27        let bit_index = if cfg!(target_endian = "big") {
28            7 - (index % 8)
29        } else {
30            index % 8
31        };
32
33        let mask = 1 << bit_index;
34
35        byte & mask == mask
36    }
37
38    #[inline]
39    pub fn set_bit(&mut self, index: usize, val: bool) {
40        debug_assert!(index / 8 < self.storage.as_ref().len());
41
42        let byte_index = index / 8;
43        let byte = &mut self.storage.as_mut()[byte_index];
44
45        let bit_index = if cfg!(target_endian = "big") {
46            7 - (index % 8)
47        } else {
48            index % 8
49        };
50
51        let mask = 1 << bit_index;
52        if val {
53            *byte |= mask;
54        } else {
55            *byte &= !mask;
56        }
57    }
58
59    #[inline]
60    pub fn get(&self, bit_offset: usize, bit_width: u8) -> u64 {
61        debug_assert!(bit_width <= 64);
62        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
63        debug_assert!((bit_offset + (bit_width as usize)) / 8 <= self.storage.as_ref().len());
64
65        let mut val = 0;
66
67        for i in 0..(bit_width as usize) {
68            if self.get_bit(i + bit_offset) {
69                let index = if cfg!(target_endian = "big") {
70                    bit_width as usize - 1 - i
71                } else {
72                    i
73                };
74                val |= 1 << index;
75            }
76        }
77
78        val
79    }
80
81    #[inline]
82    pub fn set(&mut self, bit_offset: usize, bit_width: u8, val: u64) {
83        debug_assert!(bit_width <= 64);
84        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
85        debug_assert!((bit_offset + (bit_width as usize)) / 8 <= self.storage.as_ref().len());
86
87        for i in 0..(bit_width as usize) {
88            let mask = 1 << i;
89            let val_bit_is_set = val & mask == mask;
90            let index = if cfg!(target_endian = "big") {
91                bit_width as usize - 1 - i
92            } else {
93                i
94            };
95            self.set_bit(index + bit_offset, val_bit_is_set);
96        }
97    }
98}
99
100#[cfg(all(test, feature = "wincode"))]
101mod wincode_prop_tests {
102    use super::*;
103    use core::mem;
104    use proptest::prelude::*;
105    use proptest::test_runner::Config as ProptestConfig;
106
107    fn round_trip(unit: &BitfieldU16) -> BitfieldU16 {
108        let mut buf = [0u8; mem::size_of::<BitfieldU16>()];
109        wincode::serialize_into(buf.as_mut_slice(), unit).unwrap();
110        wincode::deserialize(&buf).unwrap()
111    }
112
113    proptest! {
114        #![proptest_config(ProptestConfig {
115            failure_persistence: None,
116            ..ProptestConfig::default()
117        })]
118
119        #[test]
120        fn bitfield_unit_round_trip(initial in proptest::array::uniform2(any::<u8>())) {
121            let mut unit = BitfieldU16::new(initial);
122            let bit = (initial[0] as usize) % (initial.len() * 8);
123            unit.set_bit(bit, true);
124
125            let via_wincode = round_trip(&unit);
126            prop_assert_eq!(via_wincode.storage, unit.storage);
127        }
128    }
129}
network_types/bitfield.rs

network_types/
bitfield.rs
