messagepack_core/decode/
nil.rs

1//! Nil and `Option` decoding helpers.
2
3use super::{Decode, Error, Result};
4use crate::formats::Format;
5
6/// Decode the MessagePack `nil` value.
7pub struct NilDecoder;
8
9impl<'a> Decode<'a> for NilDecoder {
10    type Value = ();
11    fn decode(buf: &'a [u8]) -> Result<(Self::Value, &'a [u8])> {
12        let (format, buf) = Format::decode(buf)?;
13
14        Self::decode_with_format(format, buf)
15    }
16
17    fn decode_with_format(format: Format, buf: &'a [u8]) -> Result<(Self::Value, &'a [u8])> {
18        match format {
19            Format::Nil => Ok(((), buf)),
20            _ => Err(Error::UnexpectedFormat),
21        }
22    }
23}
24
25impl<'a> Decode<'a> for () {
26    type Value = ();
27    fn decode(buf: &'a [u8]) -> Result<(Self::Value, &'a [u8])> {
28        NilDecoder::decode(buf)
29    }
30    fn decode_with_format(format: Format, buf: &'a [u8]) -> Result<(Self::Value, &'a [u8])> {
31        NilDecoder::decode_with_format(format, buf)
32    }
33}
34
35impl<'a, V> Decode<'a> for Option<V>
36where
37    V: Decode<'a>,
38{
39    type Value = Option<V::Value>;
40    fn decode(buf: &'a [u8]) -> Result<(Self::Value, &'a [u8])> {
41        let (format, buf) = Format::decode(buf)?;
42        Self::decode_with_format(format, buf)
43    }
44    fn decode_with_format(format: Format, buf: &'a [u8]) -> Result<(Self::Value, &'a [u8])> {
45        match format {
46            Format::Nil => Ok((None, buf)),
47            other => {
48                let (val, buf) = V::decode_with_format(other, buf)?;
49                Ok((Some(val), buf))
50            }
51        }
52    }
53}
54
55#[cfg(test)]
56mod tests {
57    use super::*;
58
59    #[test]
60    fn decode_nil() {
61        let buf: &[u8] = &[0xc0];
62        let (_, rest) = NilDecoder::decode(buf).unwrap();
63        assert_eq!(rest.len(), 0);
64    }
65
66    #[test]
67    fn decode_option() {
68        let buf: &[u8] = &[0xc0];
69        let (decoded, rest) = Option::<bool>::decode(buf).unwrap();
70        assert_eq!(decoded, None);
71        assert_eq!(rest.len(), 0);
72
73        let buf: &[u8] = &[0xc3];
74        let (decoded, rest) = Option::<bool>::decode(buf).unwrap();
75        assert_eq!(decoded, Some(true));
76        assert_eq!(rest.len(), 0);
77    }
78}
messagepack_core/decode/nil.rs

messagepack_core/decode/
nil.rs
