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    //! Bit level parsers
    //!

    use crate::error::{ErrorKind, ParseError};
    use crate::internal::{Err, IResult, Needed};
    use crate::lib::std::ops::{AddAssign, Div, RangeFrom, Shl, Shr};
    use crate::traits::{InputIter, InputLength, Slice, ToUsize};

    /// Generates a parser taking `count` bits
    pub fn take<I, O, C, E: ParseError<(I, usize)>>(
      count: C,
    ) -> impl Fn((I, usize)) -> IResult<(I, usize), O, E>
    where
      I: Slice<RangeFrom<usize>> + InputIter<Item = u8> + InputLength,
      C: ToUsize,
      O: From<u8> + AddAssign + Shl<usize, Output = O> + Shr<usize, Output = O>,
    {
      let count = count.to_usize();
      move |(input, bit_offset): (I, usize)| {
        if count == 0 {
          Ok(((input, bit_offset), 0u8.into()))
        } else {
          let cnt = (count + bit_offset).div(8);
          if input.input_len() * 8 < count + bit_offset {
            Err(Err::Incomplete(Needed::new(count as usize)))
          } else {
            let mut acc: O = 0_u8.into();
            let mut offset: usize = bit_offset;
            let mut remaining: usize = count;
            let mut end_offset: usize = 0;

            for byte in input.iter_elements().take(cnt + 1) {
              if remaining == 0 {
                break;
              }
              let val: O = if offset == 0 {
                byte.into()
              } else {
                ((byte << offset) as u8 >> offset).into()
              };

              if remaining < 8 - offset {
                acc += val >> (8 - offset - remaining);
                end_offset = remaining + offset;
                break;
              } else {
                acc += val << (remaining - (8 - offset));
                remaining -= 8 - offset;
                offset = 0;
              }
            }
            Ok(((input.slice(cnt..), end_offset), acc))
          }
        }
      }
    }

    /// Generates a parser taking `count` bits and comparing them to `pattern`
    pub fn tag<I, O, C, E: ParseError<(I, usize)>>(
      pattern: O,
      count: C,
    ) -> impl Fn((I, usize)) -> IResult<(I, usize), O, E>
    where
      I: Slice<RangeFrom<usize>> + InputIter<Item = u8> + InputLength + Clone,
      C: ToUsize,
      O: From<u8> + AddAssign + Shl<usize, Output = O> + Shr<usize, Output = O> + PartialEq,
    {
      let count = count.to_usize();
      move |input: (I, usize)| {
        let inp = input.clone();

        take(count)(input).and_then(|(i, o)| {
          if pattern == o {
            Ok((i, o))
          } else {
            Err(Err::Error(error_position!(inp, ErrorKind::TagBits)))
          }
        })
      }
    }

    /// Parses one specific bit as a bool.
    ///
    /// # Example
    /// ```rust
    /// # use nom::bits::complete::bool;
    /// # use nom::IResult;
    /// # use nom::error::{Error, ErrorKind};
    ///
    /// fn parse(input: (&[u8], usize)) -> IResult<(&[u8], usize), bool> {
    ///     bool(input)
    /// }
    ///
    /// assert_eq!(parse(([0b10000000].as_ref(), 0)), Ok((([0b10000000].as_ref(), 1), true)));
    /// assert_eq!(parse(([0b10000000].as_ref(), 1)), Ok((([0b10000000].as_ref(), 2), false)));
    /// ```
    pub fn bool<I, E: ParseError<(I, usize)>>(input: (I, usize)) -> IResult<(I, usize), bool, E>
    where
      I: Slice<RangeFrom<usize>> + InputIter<Item = u8> + InputLength,
    {
      let (res, bit): (_, u32) = take(1usize)(input)?;
      Ok((res, bit != 0))
    }

    #[cfg(test)]
    mod test {
      use super::*;

      #[test]
      fn test_take_0() {
        let input = [].as_ref();
        let count = 0usize;
        assert_eq!(count, 0usize);
        let offset = 0usize;

        let result: crate::IResult<(&[u8], usize), usize> = take(count)((input, offset));

        assert_eq!(result, Ok(((input, offset), 0)));
      }

      #[test]
      fn test_tag_ok() {
        let input = [0b00011111].as_ref();
        let offset = 0usize;
        let bits_to_take = 4usize;
        let value_to_tag = 0b0001;

        let result: crate::IResult<(&[u8], usize), usize> =
          tag(value_to_tag, bits_to_take)((input, offset));

        assert_eq!(result, Ok(((input, bits_to_take), value_to_tag)));
      }

      #[test]
      fn test_tag_err() {
        let input = [0b00011111].as_ref();
        let offset = 0usize;
        let bits_to_take = 4usize;
        let value_to_tag = 0b1111;

        let result: crate::IResult<(&[u8], usize), usize> =
          tag(value_to_tag, bits_to_take)((input, offset));

        assert_eq!(
          result,
          Err(crate::Err::Error(crate::error::Error {
            input: (input, offset),
            code: ErrorKind::TagBits
          }))
        );
      }

      #[test]
      fn test_bool_0() {
        let input = [0b10000000].as_ref();

        let result: crate::IResult<(&[u8], usize), bool> = bool((input, 0));

        assert_eq!(result, Ok(((input, 1), true)));
      }

      #[test]
      fn test_bool_eof() {
        let input = [0b10000000].as_ref();

        let result: crate::IResult<(&[u8], usize), bool> = bool((input, 8));

        assert_eq!(result, Err(crate::Err::Incomplete(Needed::new(1))));
      }
    }