messagepack-core 0.2.4

messagepack for `no_std`
Documentation 
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//! Array format encoder.

use super::{Encode, Error, Result};
use crate::{formats::Format, io::IoWrite};

/// Encode only the array header for an array of a given length.
pub struct ArrayFormatEncoder(pub usize);

impl Encode for ArrayFormatEncoder {
    fn encode<W: IoWrite>(&self, writer: &mut W) -> Result<usize, <W as IoWrite>::Error> {
        match self.0 {
            0x00..=0b1111 => {
                let cast = self.0 as u8;
                writer.write(&[Format::FixArray(cast).as_byte()])?;
                Ok(1)
            }
            0x10..=0xffff => {
                let cast = (self.0 as u16).to_be_bytes();
                writer.write(&[Format::Array16.as_byte(), cast[0], cast[1]])?;

                Ok(3)
            }
            0x10000..=0xffffffff => {
                let cast = (self.0 as u32).to_be_bytes();
                writer.write(&[
                    Format::Array32.as_byte(),
                    cast[0],
                    cast[1],
                    cast[2],
                    cast[3],
                ])?;

                Ok(5)
            }
            _ => Err(Error::InvalidFormat),
        }
    }
}

impl<V: Encode> Encode for &[V] {
    fn encode<W: IoWrite>(&self, writer: &mut W) -> Result<usize, <W as IoWrite>::Error> {
        let format_len = ArrayFormatEncoder(self.len()).encode(writer)?;
        let array_len = self
            .iter()
            .map(|v| v.encode(writer))
            .try_fold(0, |acc, v| v.map(|n| acc + n))?;
        Ok(format_len + array_len)
    }
}

impl<const N: usize, V: Encode> Encode for [V; N] {
    fn encode<W: IoWrite>(&self, writer: &mut W) -> Result<usize, <W as IoWrite>::Error> {
        self.as_slice().encode(writer)
    }
}

macro_rules! tuple_impls {
    ($($len:expr => ($($n:tt $name:ident)+))+ $(,)?) => {
        $(
            tuple_impls!(@impl $len; $($n $name)+);
        )+
    };
    (@impl $len:expr; $($n:tt $name:ident)+) => {
        impl<$($name: Encode),+> Encode for ($($name,)+) {
            fn encode<W: IoWrite>(&self, writer: &mut W) -> Result<usize, <W as IoWrite>::Error> {
                let format_len = ArrayFormatEncoder($len).encode(writer)?;
                let mut array_len = 0;
                $(
                    array_len += self.$n.encode(writer)?;
                )+
                Ok(format_len + array_len)
            }
        }
    };
}

tuple_impls! {
    1  => (0 V0)
    2  => (0 V0 1 V1)
    3  => (0 V0 1 V1 2 V2)
    4  => (0 V0 1 V1 2 V2 3 V3)
    5  => (0 V0 1 V1 2 V2 3 V3 4 V4)
    6  => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5)
    7  => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6)
    8  => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7)
    9  => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8)
    10 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9)
    11 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9 10 V10)
    12 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9 10 V10 11 V11)
    13 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9 10 V10 11 V11 12 V12)
    14 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9 10 V10 11 V11 12 V12 13 V13)
    15 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9 10 V10 11 V11 12 V12 13 V13 14 V14)
    16 => (0 V0 1 V1 2 V2 3 V3 4 V4 5 V5 6 V6 7 V7 8 V8 9 V9 10 V10 11 V11 12 V12 13 V13 14 V14 15 V15)
}

#[cfg(feature = "alloc")]
impl<V: Encode> Encode for alloc::vec::Vec<V> {
    fn encode<W: IoWrite>(&self, writer: &mut W) -> Result<usize, <W as IoWrite>::Error> {
        self.as_slice().encode(writer)
    }
}

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

    #[rstest]
    #[case([1u8, 2u8, 3u8],[0x93, 0x01, 0x02, 0x03])]
    fn encode_fix_array<V: Encode, Array: AsRef<[V]>, E: AsRef<[u8]> + Sized>(
        #[case] value: Array,
        #[case] expected: E,
    ) {
        let expected = expected.as_ref();

        let mut buf = vec![];
        let n = value.as_ref().encode(&mut buf).unwrap();
        assert_eq!(buf, expected);
        assert_eq!(n, expected.len());
    }

    #[rstest]
    #[case(0xdc, 65535_u16.to_be_bytes(),[0x34;65535])]
    #[case(0xdd, 65536_u32.to_be_bytes(),[0x56;65536])]
    fn encode_array_sized<S: AsRef<[u8]>, D: AsRef<[u8]>>(
        #[case] marker: u8,
        #[case] size: S,
        #[case] data: D,
    ) {
        let expected = marker
            .to_be_bytes()
            .iter()
            .chain(size.as_ref())
            .chain(data.as_ref())
            .cloned()
            .collect::<Vec<u8>>();

        let mut buf = vec![];
        let n = data.as_ref().encode(&mut buf).unwrap();

        assert_eq!(&buf, &expected);
        assert_eq!(n, expected.len());
    }

    #[rstest]
    #[case((1u8,), &[0x91,0x01])]
    #[case((1u8,2u8), &[0x92,0x01,0x02])]
    #[case((1u8,2u8,3u8), &[0x93,0x01,0x02,0x03])]
    fn encode_tuple<V: Encode>(#[case] v: V, #[case] expected: &[u8]) {
        let mut buf = Vec::new();
        let _ = v.encode(&mut buf).unwrap();
        assert_eq!(buf, expected);
    }

    #[cfg(feature = "alloc")]
    #[test]
    fn encode_vec_via_slice() {
        let v = alloc::vec![1u8, 2, 3];
        let mut buf = alloc::vec::Vec::new();
        let _ = v.encode(&mut buf).unwrap();
        assert_eq!(buf, alloc::vec![0x93, 0x01, 0x02, 0x03]);
    }
}