# lib.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/bit_field-0.10.1/src/lib.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Provides the abstraction of a bit field, which allows for bit-level update and retrieval
    //! operations.

    #![no_std]

    #[cfg(test)]
    mod tests;

    use core::ops::{Bound, Range, RangeBounds};

    /// A generic trait which provides methods for extracting and setting specific bits or ranges of
    /// bits.
    pub trait BitField {
        /// The number of bits in this bit field.
        ///
        /// ```rust
        /// use bit_field::BitField;
        ///
        /// assert_eq!(u32::BIT_LENGTH, 32);
        /// assert_eq!(u64::BIT_LENGTH, 64);
        /// ```
        const BIT_LENGTH: usize;

        /// Obtains the bit at the index `bit`; note that index 0 is the least significant bit, while
        /// index `length() - 1` is the most significant bit.
        ///
        /// ```rust
        /// use bit_field::BitField;
        ///
        /// let value: u32 = 0b110101;
        ///
        /// assert_eq!(value.get_bit(1), false);
        /// assert_eq!(value.get_bit(2), true);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the bit index is out of bounds of the bit field.
        fn get_bit(&self, bit: usize) -> bool;

        /// Obtains the range of bits specified by `range`; note that index 0 is the least significant
        /// bit, while index `length() - 1` is the most significant bit.
        ///
        /// ```rust
        /// use bit_field::BitField;
        ///
        /// let value: u32 = 0b110101;
        ///
        /// assert_eq!(value.get_bits(0..3), 0b101);
        /// assert_eq!(value.get_bits(2..6), 0b1101);
        /// assert_eq!(value.get_bits(..), 0b110101);
        /// assert_eq!(value.get_bits(3..=3), value.get_bit(3) as u32);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the start or end indexes of the range are out of bounds of the
        /// bit field.
        fn get_bits<T: RangeBounds<usize>>(&self, range: T) -> Self;

        /// Sets the bit at the index `bit` to the value `value` (where true means a value of '1' and
        /// false means a value of '0'); note that index 0 is the least significant bit, while index
        /// `length() - 1` is the most significant bit.
        ///
        /// ```rust
        /// use bit_field::BitField;
        ///
        /// let mut value = 0u32;
        ///
        /// value.set_bit(1, true);
        /// assert_eq!(value, 2u32);
        ///
        /// value.set_bit(3, true);
        /// assert_eq!(value, 10u32);
        ///
        /// value.set_bit(1, false);
        /// assert_eq!(value, 8u32);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the bit index is out of the bounds of the bit field.
        fn set_bit(&mut self, bit: usize, value: bool) -> &mut Self;

        /// Sets the range of bits defined by the range `range` to the lower bits of `value`; to be
        /// specific, if the range is N bits long, the N lower bits of `value` will be used; if any of
        /// the other bits in `value` are set to 1, this function will panic.
        ///
        /// ```rust
        /// use bit_field::BitField;
        ///
        /// let mut value = 0u32;
        ///
        /// value.set_bits(0..2, 0b11);
        /// assert_eq!(value, 0b11);
        ///
        /// value.set_bits(2..=3, 0b11);
        /// assert_eq!(value, 0b1111);
        ///
        /// value.set_bits(..4, 0b1010);
        /// assert_eq!(value, 0b1010);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the range is out of bounds of the bit field, or if there are `1`s
        /// not in the lower N bits of `value`.
        fn set_bits<T: RangeBounds<usize>>(&mut self, range: T, value: Self) -> &mut Self;
    }

    pub trait BitArray<T: BitField> {
        /// Returns the length, eg number of bits, in this bit array.
        ///
        /// ```rust
        /// use bit_field::BitArray;
        ///
        /// assert_eq!([0u8, 4u8, 8u8].bit_length(), 24);
        /// assert_eq!([0u32, 5u32].bit_length(), 64);
        /// ```
        fn bit_length(&self) -> usize;

        /// Obtains the bit at the index `bit`; note that index 0 is the least significant bit, while
        /// index `length() - 1` is the most significant bit.
        ///
        /// ```rust
        /// use bit_field::BitArray;
        ///
        /// let value: [u32; 1] = [0b110101];
        ///
        /// assert_eq!(value.get_bit(1), false);
        /// assert_eq!(value.get_bit(2), true);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the bit index is out of bounds of the bit array.
        fn get_bit(&self, bit: usize) -> bool;

        /// Obtains the range of bits specified by `range`; note that index 0 is the least significant
        /// bit, while index `length() - 1` is the most significant bit.
        ///
        /// ```rust
        /// use bit_field::BitArray;
        ///
        /// let value: [u32; 2] = [0b110101, 0b11];
        ///
        /// assert_eq!(value.get_bits(0..3), 0b101);
        /// assert_eq!(value.get_bits(..6), 0b110101);
        /// assert_eq!(value.get_bits(31..33), 0b10);
        /// assert_eq!(value.get_bits(5..=32), 0b1_0000_0000_0000_0000_0000_0000_001);
        /// assert_eq!(value.get_bits(34..), 0);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the start or end indexes of the range are out of bounds of the
        /// bit array, or if the range can't be contained by the bit field T.
        fn get_bits<U: RangeBounds<usize>>(&self, range: U) -> T;

        /// Sets the bit at the index `bit` to the value `value` (where true means a value of '1' and
        /// false means a value of '0'); note that index 0 is the least significant bit, while index
        /// `length() - 1` is the most significant bit.
        ///
        /// ```rust
        /// use bit_field::BitArray;
        ///
        /// let mut value = [0u32];
        ///
        /// value.set_bit(1, true);
        /// assert_eq!(value, [2u32]);
        ///
        /// value.set_bit(3, true);
        /// assert_eq!(value, [10u32]);
        ///
        /// value.set_bit(1, false);
        /// assert_eq!(value, [8u32]);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the bit index is out of the bounds of the bit array.
        fn set_bit(&mut self, bit: usize, value: bool);

        /// Sets the range of bits defined by the range `range` to the lower bits of `value`; to be
        /// specific, if the range is N bits long, the N lower bits of `value` will be used; if any of
        /// the other bits in `value` are set to 1, this function will panic.
        ///
        /// ```rust
        /// use bit_field::BitArray;
        ///
        /// let mut value = [0u32, 0u32];
        ///
        /// value.set_bits(0..2, 0b11);
        /// assert_eq!(value, [0b11, 0u32]);
        ///
        /// value.set_bits(31..35, 0b1010);
        /// assert_eq!(value, [0x0003, 0b101]);
        /// ```
        ///
        /// ## Panics
        ///
        /// This method will panic if the range is out of bounds of the bit array,
        /// if the range can't be contained by the bit field T, or if there are `1`s
        /// not in the lower N bits of `value`.
        fn set_bits<U: RangeBounds<usize>>(&mut self, range: U, value: T);
    }

    /// An internal macro used for implementing BitField on the standard integral types.
    macro_rules! bitfield_numeric_impl {
        ($($t:ty)*) => ($(
            impl BitField for $t {
                const BIT_LENGTH: usize = ::core::mem::size_of::<Self>() as usize * 8;

                #[inline]
                fn get_bit(&self, bit: usize) -> bool {
                    assert!(bit < Self::BIT_LENGTH);

                    (*self & (1 << bit)) != 0
                }

                #[inline]
                fn get_bits<T: RangeBounds<usize>>(&self, range: T) -> Self {
                    let range = to_regular_range(&range, Self::BIT_LENGTH);

                    assert!(range.start < Self::BIT_LENGTH);
                    assert!(range.end <= Self::BIT_LENGTH);
                    assert!(range.start < range.end);

                    // shift away high bits
                    let bits = *self << (Self::BIT_LENGTH - range.end) >> (Self::BIT_LENGTH - range.end);

                    // shift away low bits
                    bits >> range.start
                }

                #[inline]
                fn set_bit(&mut self, bit: usize, value: bool) -> &mut Self {
                    assert!(bit < Self::BIT_LENGTH);

                    if value {
                        *self |= 1 << bit;
                    } else {
                        *self &= !(1 << bit);
                    }

                    self
                }

                #[inline]
                fn set_bits<T: RangeBounds<usize>>(&mut self, range: T, value: Self) -> &mut Self {
                    let range = to_regular_range(&range, Self::BIT_LENGTH);

                    assert!(range.start < Self::BIT_LENGTH);
                    assert!(range.end <= Self::BIT_LENGTH);
                    assert!(range.start < range.end);
                    assert!(value << (Self::BIT_LENGTH - (range.end - range.start)) >>
                            (Self::BIT_LENGTH - (range.end - range.start)) == value,
                            "value does not fit into bit range");

                    let bitmask: Self = !(!0 << (Self::BIT_LENGTH - range.end) >>
                                        (Self::BIT_LENGTH - range.end) >>
                                        range.start << range.start);

                    // set bits
                    *self = (*self & bitmask) | (value << range.start);

                    self
                }
            }
        )*)
    }

    bitfield_numeric_impl! { u8 u16 u32 u64 u128 usize i8 i16 i32 i64 i128 isize }

    impl<T: BitField> BitArray<T> for [T] {
        #[inline]
        fn bit_length(&self) -> usize {
            self.len() * T::BIT_LENGTH
        }

        #[inline]
        fn get_bit(&self, bit: usize) -> bool {
            let slice_index = bit / T::BIT_LENGTH;
            let bit_index = bit % T::BIT_LENGTH;
            self[slice_index].get_bit(bit_index)
        }

        #[inline]
        fn get_bits<U: RangeBounds<usize>>(&self, range: U) -> T {
            let range = to_regular_range(&range, self.bit_length());

            assert!(range.len() <= T::BIT_LENGTH);

            let slice_start = range.start / T::BIT_LENGTH;
            let slice_end = range.end / T::BIT_LENGTH;
            let bit_start = range.start % T::BIT_LENGTH;
            let bit_end = range.end % T::BIT_LENGTH;
            let len = range.len();

            assert!(slice_end - slice_start <= 1);

            if slice_start == slice_end {
                self[slice_start].get_bits(bit_start..bit_end)
            } else if bit_end == 0 {
                self[slice_start].get_bits(bit_start..T::BIT_LENGTH)
            } else {
                let mut ret = self[slice_start].get_bits(bit_start..T::BIT_LENGTH);
                ret.set_bits(
                    (T::BIT_LENGTH - bit_start)..len,
                    self[slice_end].get_bits(0..bit_end),
                );
                ret
            }
        }

        #[inline]
        fn set_bit(&mut self, bit: usize, value: bool) {
            let slice_index = bit / T::BIT_LENGTH;
            let bit_index = bit % T::BIT_LENGTH;
            self[slice_index].set_bit(bit_index, value);
        }

        #[inline]
        fn set_bits<U: RangeBounds<usize>>(&mut self, range: U, value: T) {
            let range = to_regular_range(&range, self.bit_length());

            assert!(range.len() <= T::BIT_LENGTH);

            let slice_start = range.start / T::BIT_LENGTH;
            let slice_end = range.end / T::BIT_LENGTH;
            let bit_start = range.start % T::BIT_LENGTH;
            let bit_end = range.end % T::BIT_LENGTH;

            assert!(slice_end - slice_start <= 1);

            if slice_start == slice_end {
                self[slice_start].set_bits(bit_start..bit_end, value);
            } else if bit_end == 0 {
                self[slice_start].set_bits(bit_start..T::BIT_LENGTH, value);
            } else {
                self[slice_start].set_bits(
                    bit_start..T::BIT_LENGTH,
                    value.get_bits(0..T::BIT_LENGTH - bit_start),
                );
                self[slice_end].set_bits(
                    0..bit_end,
                    value.get_bits(T::BIT_LENGTH - bit_start..T::BIT_LENGTH),
                );
            }
        }
    }

    fn to_regular_range<T: RangeBounds<usize>>(generic_rage: &T, bit_length: usize) -> Range<usize> {
        let start = match generic_rage.start_bound() {
            Bound::Excluded(&value) => value + 1,
            Bound::Included(&value) => value,
            Bound::Unbounded => 0,
        };
        let end = match generic_rage.end_bound() {
            Bound::Excluded(&value) => value,
            Bound::Included(&value) => value + 1,
            Bound::Unbounded => bit_length,
        };

        start..end
    }