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Fix #1500: Add example for bits::complete::tag
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Adam Chalmers committed Feb 18, 2022
1 parent e99f9e0 commit 781e36a
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43 changes: 43 additions & 0 deletions src/bits/complete.rs
Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,49 @@ where
}

/// Generates a parser taking `count` bits and comparing them to `pattern`
///
/// # Example
/// ```rust
///
/// use nom::error::{Error, ErrorKind};
///
/// /// Compare the lowest `count` bits of `input` against the lowest `count` bits of `pattern`.
/// /// Return Ok and the matching section of `input` if there's a match.
/// /// Return Err if there's no match.
/// fn parser(pattern: u8, count: u8, input: (&[u8], usize)) -> nom::IResult<(&[u8], usize), u8> {
/// nom::bits::complete::tag(pattern, count)(input)
/// }
///
/// // The lowest 4 bits of 0b00001111 match the lowest 4 bits of 0b11111111.
/// assert_eq!(
/// parser(0b0000_1111, 4, ([0b1111_1111].as_ref(), 0)),
/// Ok((([0b1111_1111]..as_ref()(), 4), 0b0000_1111))
/// );
///
/// // The lowest bit of 0b00001111 matches the lowest bit of 0b11111111 (both are 1).
/// assert_eq!(
/// parser(0b00000001, 1, ([0b11111111].as_ref(), 0)),
/// Ok((([0b11111111]..as_ref()(), 1), 0b00000001))
/// );
///
/// // The lowest 2 bits of 0b11111111 and 0b00000001 are different.
/// assert_eq!(
/// parser(0b000000_01, 2, ([0b111111_11].as_ref(), 0)),
/// Err(nom::Err::Error(Error {
/// input: ([0b11111111].as_ref(), 0),
/// code: ErrorKind::TagBits
/// }))
/// );
///
/// // The lowest 8 bits of 0b11111111 and 0b11111110 are different.
/// assert_eq!(
/// parser(0b11111110, 8, ([0b11111111].as_ref(), 0)),
/// Err(nom::Err::Error(Error {
/// input: ([0b11111111].as_ref(), 0),
/// code: ErrorKind::TagBits
/// }))
/// );
/// ```
pub fn tag<I, O, C, E: ParseError<(I, usize)>>(
pattern: O,
count: C,
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