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    type Cfg = ();
39
40    fn read_cfg(buf: &mut impl Buf, _: &()) -> Result<Self, CodecError> {
41        Ok(Self(<[u8; N]>::read(buf)?))
42    }
43}
44
45impl<const N: usize> FixedSize for FixedBytes<N> {
46    const SIZE: usize = N;
47}
48
49impl<const N: usize> Array for FixedBytes<N> {}
50
51impl<const N: usize> AsRef<[u8]> for FixedBytes<N> {
52    fn as_ref(&self) -> &[u8] {
53        &self.0
54    }
55}
56
57impl<const N: usize> Deref for FixedBytes<N> {
58    type Target = [u8];
59    fn deref(&self) -> &[u8] {
60        &self.0
61    }
62}
63
64impl<const N: usize> Display for FixedBytes<N> {
65    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
66        write!(f, "{}", hex(&self.0))
67    }
68}
69
70#[cfg(test)]
71mod tests {
72    use super::*;
73    use bytes::{Buf, BytesMut};
74    use commonware_codec::{DecodeExt, Encode};
75
76    #[test]
77    fn test_codec() {
78        let original = FixedBytes::new([1, 2, 3, 4]);
79        let encoded = original.encode();
80        assert_eq!(encoded.len(), original.len());
81        let decoded = FixedBytes::decode(encoded).unwrap();
82        assert_eq!(original, decoded);
83    }
84
85    #[test]
86    fn test_bytes_creation_and_conversion() {
87        let value = [1, 2, 3, 4];
88        let bytes = FixedBytes::new(value);
89        assert_eq!(bytes.as_ref(), &value);
90
91        let slice = [1, 2, 3, 4];
92        let bytes_from_slice = FixedBytes::decode(slice.as_ref()).unwrap();
93        assert_eq!(bytes_from_slice, bytes);
94
95        let vec = vec![1, 2, 3, 4];
96        let bytes_from_vec = FixedBytes::decode(vec.as_ref()).unwrap();
97        assert_eq!(bytes_from_vec, bytes);
98
99        // Test with incorrect length
100        let slice_too_short = [1, 2, 3];
101        assert!(matches!(
102            FixedBytes::<4>::decode(slice_too_short.as_ref()),
103            Err(CodecError::EndOfBuffer)
104        ));
105
106        let vec_too_long = vec![1, 2, 3, 4, 5];
107        assert!(matches!(
108            FixedBytes::<4>::decode(vec_too_long.as_ref()),
109            Err(CodecError::ExtraData(1))
110        ));
111    }
112
113    #[test]
114    fn test_read() {
115        let mut buf = BytesMut::from(&[1, 2, 3, 4][..]);
116        let bytes = FixedBytes::<4>::read(&mut buf).unwrap();
117        assert_eq!(bytes.as_ref(), &[1, 2, 3, 4]);
118        assert_eq!(buf.remaining(), 0);
119
120        let mut buf = BytesMut::from(&[1, 2, 3][..]);
121        let result = FixedBytes::<4>::read(&mut buf);
122        assert!(matches!(result, Err(CodecError::EndOfBuffer)));
123
124        let mut buf = BytesMut::from(&[1, 2, 3, 4, 5][..]);
125        let bytes = FixedBytes::<4>::read(&mut buf).unwrap();
126        assert_eq!(bytes.as_ref(), &[1, 2, 3, 4]);
127        assert_eq!(buf.remaining(), 1);
128        assert_eq!(buf[0], 5);
129    }
130
131    #[test]
132    fn test_display() {
133        let bytes = FixedBytes::new([0x01, 0x02, 0x03, 0x04]);
134        assert_eq!(format!("{}", bytes), "01020304");
135    }
136
137    #[test]
138    fn test_ord_and_eq() {
139        let a = FixedBytes::new([1, 2, 3, 4]);
140        let b = FixedBytes::new([1, 2, 3, 5]);
141        assert!(a < b);
142        assert_ne!(a, b);
143
144        let c = FixedBytes::new([1, 2, 3, 4]);
145        assert_eq!(a, c);
146    }
147}
commonware_utils/array/fixed_bytes.rs

commonware_utils/array/
fixed_bytes.rs
