network-types 0.2.0

Rust structs representing network-related types in Linux.
Documentation 
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//! A Rust bitfield implementation, copied from
//! [bindgen](https://github.com/rust-lang/rust-bindgen/blob/master/bindgen/codegen/bitfield_unit.rs)
//! which is licensed under the
//! [BSD 3-Clause license](https://github.com/rust-lang/rust-bindgen/blob/master/LICENSE).

#[repr(C)]
#[derive(Copy, Clone, Debug, Default, Eq, Hash, Ord, PartialEq, PartialOrd)]
#[cfg_attr(feature = "wincode", derive(wincode::SchemaRead, wincode::SchemaWrite))]
#[cfg_attr(feature = "wincode", wincode(assert_zero_copy))]
pub struct BitfieldU16 {
    storage: [u8; 2],
}

impl BitfieldU16 {
    #[inline]
    pub const fn new(storage: [u8; 2]) -> Self {
        Self { storage }
    }

    #[inline]
    pub fn get_bit(&self, index: usize) -> bool {
        debug_assert!(index / 8 < self.storage.as_ref().len());

        let byte_index = index / 8;
        let byte = self.storage.as_ref()[byte_index];

        let bit_index = if cfg!(target_endian = "big") {
            7 - (index % 8)
        } else {
            index % 8
        };

        let mask = 1 << bit_index;

        byte & mask == mask
    }

    #[inline]
    pub fn set_bit(&mut self, index: usize, val: bool) {
        debug_assert!(index / 8 < self.storage.as_ref().len());

        let byte_index = index / 8;
        let byte = &mut self.storage.as_mut()[byte_index];

        let bit_index = if cfg!(target_endian = "big") {
            7 - (index % 8)
        } else {
            index % 8
        };

        let mask = 1 << bit_index;
        if val {
            *byte |= mask;
        } else {
            *byte &= !mask;
        }
    }

    #[inline]
    pub fn get(&self, bit_offset: usize, bit_width: u8) -> u64 {
        debug_assert!(bit_width <= 64);
        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
        debug_assert!((bit_offset + (bit_width as usize)) / 8 <= self.storage.as_ref().len());

        let mut val = 0;

        for i in 0..(bit_width as usize) {
            if self.get_bit(i + bit_offset) {
                let index = if cfg!(target_endian = "big") {
                    bit_width as usize - 1 - i
                } else {
                    i
                };
                val |= 1 << index;
            }
        }

        val
    }

    #[inline]
    pub fn set(&mut self, bit_offset: usize, bit_width: u8, val: u64) {
        debug_assert!(bit_width <= 64);
        debug_assert!(bit_offset / 8 < self.storage.as_ref().len());
        debug_assert!((bit_offset + (bit_width as usize)) / 8 <= self.storage.as_ref().len());

        for i in 0..(bit_width as usize) {
            let mask = 1 << i;
            let val_bit_is_set = val & mask == mask;
            let index = if cfg!(target_endian = "big") {
                bit_width as usize - 1 - i
            } else {
                i
            };
            self.set_bit(index + bit_offset, val_bit_is_set);
        }
    }
}

#[cfg(all(test, feature = "wincode"))]
mod wincode_prop_tests {
    use super::*;
    use core::mem;
    use proptest::prelude::*;
    use proptest::test_runner::Config as ProptestConfig;

    fn round_trip(unit: &BitfieldU16) -> BitfieldU16 {
        let mut buf = [0u8; mem::size_of::<BitfieldU16>()];
        wincode::serialize_into(buf.as_mut_slice(), unit).unwrap();
        wincode::deserialize(&buf).unwrap()
    }

    proptest! {
        #![proptest_config(ProptestConfig {
            failure_persistence: None,
            ..ProptestConfig::default()
        })]

        #[test]
        fn bitfield_unit_round_trip(initial in proptest::array::uniform2(any::<u8>())) {
            let mut unit = BitfieldU16::new(initial);
            let bit = (initial[0] as usize) % (initial.len() * 8);
            unit.set_bit(bit, true);

            let via_wincode = round_trip(&unit);
            prop_assert_eq!(via_wincode.storage, unit.storage);
        }
    }
}