commonware_utils/array/
fixed_bytes.rs

1use crate::{hex, Array};
2use bytes::{Buf, BufMut};
3use commonware_codec::{Error as CodecError, FixedSize, Read, ReadExt, Write};
4use std::{
5    cmp::{Ord, PartialOrd},
6    fmt::{Debug, Display},
7    hash::Hash,
8    ops::Deref,
9};
10use thiserror::Error;
11
12/// Errors returned by `Bytes` functions.
13#[derive(Error, Debug, PartialEq)]
14pub enum Error {
15    #[error("invalid length")]
16    InvalidLength,
17}
18
19/// An `Array` implementation for fixed-length byte arrays.
20#[derive(Clone, Eq, PartialEq, Ord, PartialOrd, Hash, Debug)]
21#[repr(transparent)]
22pub struct FixedBytes<const N: usize>([u8; N]);
23
24impl<const N: usize> FixedBytes<N> {
25    /// Creates a new `FixedBytes` instance from an array of length `N`.
26    pub fn new(value: [u8; N]) -> Self {
27        Self(value)
28    }
29}
30
31impl<const N: usize> Write for FixedBytes<N> {
32    fn write(&self, buf: &mut impl BufMut) {
33        self.0.write(buf);
34    }
35}
36
37impl<const N: usize> Read for FixedBytes<N> {
38    fn read_cfg(buf: &mut impl Buf, _: &()) -> Result<Self, CodecError> {
39        Ok(Self(<[u8; N]>::read(buf)?))
40    }
41}
42
43impl<const N: usize> FixedSize for FixedBytes<N> {
44    const SIZE: usize = N;
45}
46
47impl<const N: usize> Array for FixedBytes<N> {}
48
49impl<const N: usize> AsRef<[u8]> for FixedBytes<N> {
50    fn as_ref(&self) -> &[u8] {
51        &self.0
52    }
53}
54
55impl<const N: usize> Deref for FixedBytes<N> {
56    type Target = [u8];
57    fn deref(&self) -> &[u8] {
58        &self.0
59    }
60}
61
62impl<const N: usize> Display for FixedBytes<N> {
63    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
64        write!(f, "{}", hex(&self.0))
65    }
66}
67
68#[cfg(test)]
69mod tests {
70    use super::*;
71    use bytes::{Buf, BytesMut};
72    use commonware_codec::{DecodeExt, Encode};
73
74    #[test]
75    fn test_codec() {
76        let original = FixedBytes::new([1, 2, 3, 4]);
77        let encoded = original.encode();
78        assert_eq!(encoded.len(), original.len());
79        let decoded = FixedBytes::decode(encoded).unwrap();
80        assert_eq!(original, decoded);
81    }
82
83    #[test]
84    fn test_bytes_creation_and_conversion() {
85        let value = [1, 2, 3, 4];
86        let bytes = FixedBytes::new(value);
87        assert_eq!(bytes.as_ref(), &value);
88
89        let slice = [1, 2, 3, 4];
90        let bytes_from_slice = FixedBytes::decode(slice.as_ref()).unwrap();
91        assert_eq!(bytes_from_slice, bytes);
92
93        let vec = vec![1, 2, 3, 4];
94        let bytes_from_vec = FixedBytes::decode(vec.as_ref()).unwrap();
95        assert_eq!(bytes_from_vec, bytes);
96
97        // Test with incorrect length
98        let slice_too_short = [1, 2, 3];
99        assert!(matches!(
100            FixedBytes::<4>::decode(slice_too_short.as_ref()),
101            Err(CodecError::EndOfBuffer)
102        ));
103
104        let vec_too_long = vec![1, 2, 3, 4, 5];
105        assert!(matches!(
106            FixedBytes::<4>::decode(vec_too_long.as_ref()),
107            Err(CodecError::ExtraData(1))
108        ));
109    }
110
111    #[test]
112    fn test_read() {
113        let mut buf = BytesMut::from(&[1, 2, 3, 4][..]);
114        let bytes = FixedBytes::<4>::read(&mut buf).unwrap();
115        assert_eq!(bytes.as_ref(), &[1, 2, 3, 4]);
116        assert_eq!(buf.remaining(), 0);
117
118        let mut buf = BytesMut::from(&[1, 2, 3][..]);
119        let result = FixedBytes::<4>::read(&mut buf);
120        assert!(matches!(result, Err(CodecError::EndOfBuffer)));
121
122        let mut buf = BytesMut::from(&[1, 2, 3, 4, 5][..]);
123        let bytes = FixedBytes::<4>::read(&mut buf).unwrap();
124        assert_eq!(bytes.as_ref(), &[1, 2, 3, 4]);
125        assert_eq!(buf.remaining(), 1);
126        assert_eq!(buf[0], 5);
127    }
128
129    #[test]
130    fn test_display() {
131        let bytes = FixedBytes::new([0x01, 0x02, 0x03, 0x04]);
132        assert_eq!(format!("{}", bytes), "01020304");
133    }
134
135    #[test]
136    fn test_ord_and_eq() {
137        let a = FixedBytes::new([1, 2, 3, 4]);
138        let b = FixedBytes::new([1, 2, 3, 5]);
139        assert!(a < b);
140        assert_ne!(a, b);
141
142        let c = FixedBytes::new([1, 2, 3, 4]);
143        assert_eq!(a, c);
144    }
145}
commonware_utils/array/fixed_bytes.rs

commonware_utils/array/
fixed_bytes.rs
