binread/

punctuated.rs

//! A module for [`Punctuated<T, P>`](Punctuated), a series of items to parse of type T separated
//! by punction of type `P`.

use crate::io::{Read, Seek};
use crate::{BinRead, BinResult, ReadOptions};
#[cfg(not(feature = "std"))]
use alloc::vec::Vec;
use core::fmt;

/// A type for seperated data. Since parsing for this type is ambiguous, you must manually specify
/// a parser using the `parse_with` attribute.
///
/// ## Example
///
/// ```rust
/// # use binread::{*, io::*};
/// use binread::punctuated::Punctuated;
///
/// #[derive(BinRead)]
/// struct MyList {
///     #[br(parse_with = Punctuated::separated)]
///     #[br(count = 3)]
///     x: Punctuated<u16, u8>,
/// }
///
/// # let mut x = Cursor::new(b"\0\x03\0\0\x02\x01\0\x01");
/// # let y: MyList = x.read_be().unwrap();
/// # assert_eq!(*y.x, vec![3, 2, 1]);
/// # assert_eq!(y.x.seperators, vec![0, 1]);
/// ```
pub struct Punctuated<T: BinRead, P: BinRead> {
    data: Vec<T>,
    pub seperators: Vec<P>,
}

impl<C: Copy + 'static, T: BinRead<Args = C>, P: BinRead<Args = ()>> Punctuated<T, P> {
    /// A parser for values seperated by another value, with no trailing punctuation.
    ///
    /// Requires a specified count.
    ///
    /// ## Example
    ///
    /// ```rust
    /// # use binread::{*, io::*};
    /// use binread::punctuated::Punctuated;
    ///
    /// #[derive(BinRead)]
    /// struct MyList {
    ///     #[br(parse_with = Punctuated::separated)]
    ///     #[br(count = 3)]
    ///     x: Punctuated<u16, u8>,
    /// }
    ///
    /// # let mut x = Cursor::new(b"\0\x03\0\0\x02\x01\0\x01");
    /// # let y: MyList = x.read_be().unwrap();
    /// # assert_eq!(*y.x, vec![3, 2, 1]);
    /// # assert_eq!(y.x.seperators, vec![0, 1]);
    /// ```
    pub fn separated<R: Read + Seek>(
        reader: &mut R,
        options: &ReadOptions,
        args: C,
    ) -> BinResult<Self> {
        let count = match options.count {
            Some(x) => x,
            None => panic!("Missing count for Punctuated"),
        };

        let mut data = Vec::with_capacity(count);
        let mut seperators = Vec::with_capacity(count.max(1) - 1);

        for i in 0..count {
            data.push(T::read_options(reader, &options, args)?);
            if i + 1 != count {
                seperators.push(P::read_options(reader, options, ())?);
            }
        }

        Ok(Self { data, seperators })
    }

    /// A parser for values seperated by another value, with trailing punctuation.
    ///
    /// Requires a specified count.
    pub fn separated_trailing<R: Read + Seek>(
        reader: &mut R,
        options: &ReadOptions,
        args: C,
    ) -> BinResult<Self> {
        let count = match options.count {
            Some(x) => x,
            None => panic!("Missing count for Punctuated"),
        };

        let mut data = Vec::with_capacity(count);
        let mut seperators = Vec::with_capacity(count);

        for _ in 0..count {
            data.push(T::read_options(reader, &options, args)?);
            seperators.push(P::read_options(reader, options, ())?);
        }

        Ok(Self { data, seperators })
    }
}

impl<T: BinRead + fmt::Debug, P: BinRead> fmt::Debug for Punctuated<T, P> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        self.data.fmt(f)
    }
}

impl<T: BinRead, P: BinRead> core::ops::Deref for Punctuated<T, P> {
    type Target = Vec<T>;

    fn deref(&self) -> &Self::Target {
        &self.data
    }
}

impl<T: BinRead, P: BinRead> core::ops::DerefMut for Punctuated<T, P> {
    fn deref_mut(&mut self) -> &mut Self::Target {
        &mut self.data
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate as binread;

    use binread::{io::Cursor, BinRead, BinReaderExt};

    #[derive(BinRead, Clone, Copy, Debug)]
    #[br(magic = 1u8)]
    struct One;

    #[derive(BinRead, Clone, Copy, Debug)]
    #[br(magic = 2u8)]
    struct Two;

    #[derive(BinRead)]
    struct PunctuatedTest {
        count: u8,

        #[br(count = count)]
        #[br(parse_with = Punctuated::separated)]
        list: Punctuated<One, Two>,
    }

    #[derive(BinRead)]
    struct PunctuatedTestTrailing {
        count: u8,

        #[br(count = count)]
        #[br(parse_with = Punctuated::separated_trailing)]
        list: Punctuated<One, Two>,
    }

    #[derive(BinRead)]
    struct MissingCount {
        #[br(parse_with = Punctuated::separated)]
        _list: Punctuated<One, Two>,
    }

    #[derive(BinRead)]
    struct MissingCountTrailing {
        #[br(parse_with = Punctuated::separated_trailing)]
        _list: Punctuated<One, Two>,
    }

    const TEST_DATA: &[u8] = b"\x03\x01\x02\x01\x02\x01";
    const TEST_DATA_TRAILING: &[u8] = b"\x03\x01\x02\x01\x02\x01\x02";

    #[test]
    fn punctuated() {
        let mut x = Cursor::new(TEST_DATA);

        let y: PunctuatedTest = x.read_be().unwrap();

        assert_eq!(y.count, 3);
        assert_eq!(y.list.len(), 3);

        // This behavior may be reworked later
        assert_eq!(format!("{:?}", y.list), "[One, One, One]");
    }

    #[test]
    fn punctuated_trailing() {
        let mut x = Cursor::new(TEST_DATA_TRAILING);

        let mut y: PunctuatedTestTrailing = x.read_be().unwrap();

        assert_eq!(y.count, 3);
        assert_eq!(y.list.len(), 3);

        let y = &mut *y.list;
        y[0] = y[1];
    }

    #[test]
    #[should_panic]
    fn missing_count() {
        let mut x = Cursor::new(TEST_DATA);

        let _: MissingCount = x.read_be().unwrap();
    }

    #[test]
    #[should_panic]
    fn missing_count_trailing() {
        let mut x = Cursor::new(TEST_DATA);

        let _: MissingCountTrailing = x.read_be().unwrap();
    }
}