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    //! Bit level parsers
    //!

    pub mod complete;
    pub mod streaming;

    use crate::error::{ErrorKind, ParseError};
    use crate::internal::{Err, IResult, Needed, Parser};
    use crate::lib::std::ops::RangeFrom;
    use crate::traits::{ErrorConvert, Slice};

    /// Converts a byte-level input to a bit-level input, for consumption by a parser that uses bits.
    ///
    /// Afterwards, the input is converted back to a byte-level parser, with any remaining bits thrown
    /// away.
    ///
    /// # Example
    /// ```
    /// use nom::bits::{bits, streaming::take};
    /// use nom::error::Error;
    /// use nom::sequence::tuple;
    /// use nom::IResult;
    ///
    /// fn parse(input: &[u8]) -> IResult<&[u8], (u8, u8)> {
    ///     bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize))))(input)
    /// }
    ///
    /// let input = &[0x12, 0x34, 0xff, 0xff];
    ///
    /// let output = parse(input).expect("We take 1.5 bytes and the input is longer than 2 bytes");
    ///
    /// // The first byte is consumed, the second byte is partially consumed and dropped.
    /// let remaining = output.0;
    /// assert_eq!(remaining, [0xff, 0xff]);
    ///
    /// let parsed = output.1;
    /// assert_eq!(parsed.0, 0x01);
    /// assert_eq!(parsed.1, 0x23);
    /// ```
    pub fn bits<I, O, E1, E2, P>(mut parser: P) -> impl FnMut(I) -> IResult<I, O, E2>
    where
      E1: ParseError<(I, usize)> + ErrorConvert<E2>,
      E2: ParseError<I>,
      I: Slice<RangeFrom<usize>>,
      P: Parser<(I, usize), O, E1>,
    {
      move |input: I| match parser.parse((input, 0)) {
        Ok(((rest, offset), result)) => {
          // If the next byte has been partially read, it will be sliced away as well.
          // The parser functions might already slice away all fully read bytes.
          // That's why `offset / 8` isn't necessarily needed at all times.
          let remaining_bytes_index = offset / 8 + if offset % 8 == 0 { 0 } else { 1 };
          Ok((rest.slice(remaining_bytes_index..), result))
        }
        Err(Err::Incomplete(n)) => Err(Err::Incomplete(n.map(|u| u.get() / 8 + 1))),
        Err(Err::Error(e)) => Err(Err::Error(e.convert())),
        Err(Err::Failure(e)) => Err(Err::Failure(e.convert())),
      }
    }

    /// Counterpart to `bits`, `bytes` transforms its bit stream input into a byte slice for the underlying
    /// parser, allowing byte-slice parsers to work on bit streams.
    ///
    /// A partial byte remaining in the input will be ignored and the given parser will start parsing
    /// at the next full byte.
    ///
    /// ```
    /// use nom::bits::{bits, bytes, streaming::take};
    /// use nom::combinator::rest;
    /// use nom::error::Error;
    /// use nom::sequence::tuple;
    /// use nom::IResult;
    ///
    /// fn parse(input: &[u8]) -> IResult<&[u8], (u8, u8, &[u8])> {
    ///   bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((
    ///     take(4usize),
    ///     take(8usize),
    ///     bytes::<_, _, Error<&[u8]>, _, _>(rest)
    ///   )))(input)
    /// }
    ///
    /// let input = &[0x12, 0x34, 0xff, 0xff];
    ///
    /// assert_eq!(parse( input ), Ok(( &[][..], (0x01, 0x23, &[0xff, 0xff][..]) )));
    /// ```
    pub fn bytes<I, O, E1, E2, P>(mut parser: P) -> impl FnMut((I, usize)) -> IResult<(I, usize), O, E2>
    where
      E1: ParseError<I> + ErrorConvert<E2>,
      E2: ParseError<(I, usize)>,
      I: Slice<RangeFrom<usize>> + Clone,
      P: Parser<I, O, E1>,
    {
      move |(input, offset): (I, usize)| {
        let inner = if offset % 8 != 0 {
          input.slice((1 + offset / 8)..)
        } else {
          input.slice((offset / 8)..)
        };
        let i = (input, offset);
        match parser.parse(inner) {
          Ok((rest, res)) => Ok(((rest, 0), res)),
          Err(Err::Incomplete(Needed::Unknown)) => Err(Err::Incomplete(Needed::Unknown)),
          Err(Err::Incomplete(Needed::Size(sz))) => Err(match sz.get().checked_mul(8) {
            Some(v) => Err::Incomplete(Needed::new(v)),
            None => Err::Failure(E2::from_error_kind(i, ErrorKind::TooLarge)),
          }),
          Err(Err::Error(e)) => Err(Err::Error(e.convert())),
          Err(Err::Failure(e)) => Err(Err::Failure(e.convert())),
        }
      }
    }

    #[cfg(test)]
    mod test {
      use super::*;
      use crate::bits::streaming::take;
      use crate::error::Error;
      use crate::sequence::tuple;

      #[test]
      /// Take the `bits` function and assert that remaining bytes are correctly returned, if the
      /// previous bytes are fully consumed
      fn test_complete_byte_consumption_bits() {
        let input = &[0x12, 0x34, 0x56, 0x78];

        // Take 3 bit slices with sizes [4, 8, 4].
        let result: IResult<&[u8], (u8, u8, u8)> =
          bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize), take(4usize))))(
            input,
          );

        let output = result.expect("We take 2 bytes and the input is longer than 2 bytes");

        let remaining = output.0;
        assert_eq!(remaining, [0x56, 0x78]);

        let parsed = output.1;
        assert_eq!(parsed.0, 0x01);
        assert_eq!(parsed.1, 0x23);
        assert_eq!(parsed.2, 0x04);
      }

      #[test]
      /// Take the `bits` function and assert that remaining bytes are correctly returned, if the
      /// previous bytes are NOT fully consumed. Partially consumed bytes are supposed to be dropped.
      /// I.e. if we consume 1.5 bytes of 4 bytes, 2 bytes will be returned, bits 13-16 will be
      /// dropped.
      fn test_partial_byte_consumption_bits() {
        let input = &[0x12, 0x34, 0x56, 0x78];

        // Take bit slices with sizes [4, 8].
        let result: IResult<&[u8], (u8, u8)> =
          bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize))))(input);

        let output = result.expect("We take 1.5 bytes and the input is longer than 2 bytes");

        let remaining = output.0;
        assert_eq!(remaining, [0x56, 0x78]);

        let parsed = output.1;
        assert_eq!(parsed.0, 0x01);
        assert_eq!(parsed.1, 0x23);
      }

      #[test]
      #[cfg(feature = "std")]
      /// Ensure that in Incomplete error is thrown, if too few bytes are passed for a given parser.
      fn test_incomplete_bits() {
        let input = &[0x12];

        // Take bit slices with sizes [4, 8].
        let result: IResult<&[u8], (u8, u8)> =
          bits::<_, _, Error<(&[u8], usize)>, _, _>(tuple((take(4usize), take(8usize))))(input);

        assert!(result.is_err());
        let error = result.err().unwrap();
        assert_eq!("Parsing requires 2 bytes/chars", error.to_string());
      }
    }