snix_castore/
digests.rs

1use bytes::Bytes;
2use data_encoding::BASE64;
3use std::str::FromStr;
4use thiserror::Error;
5
6#[derive(Clone, Copy, PartialEq, Eq, Hash)]
7#[cfg_attr(feature = "serde", derive(serde_with::SerializeDisplay))]
8#[repr(transparent)]
9pub struct B3Digest([u8; Self::LENGTH]);
10
11impl B3Digest {
12    pub const LENGTH: usize = blake3::OUT_LEN;
13    /// The digest of the empty slice.
14    pub const EMPTY: Self = B3Digest([
15        0xaf, 0x13, 0x49, 0xb9, 0xf5, 0xf9, 0xa1, 0xa6, 0xa0, 0x40, 0x4d, 0xea, 0x36, 0xdc, 0xc9,
16        0x49, 0x9b, 0xcb, 0x25, 0xc9, 0xad, 0xc1, 0x12, 0xb7, 0xcc, 0x9a, 0x93, 0xca, 0xe4, 0x1f,
17        0x32, 0x62,
18    ]);
19}
20
21#[derive(Error, Debug, PartialEq)]
22pub enum Error {
23    #[error("invalid digest length: {0}")]
24    InvalidDigestLen(usize),
25    #[error("invalid hash type: expected a 'blake3-' prefixed digest")]
26    InvalidHashType,
27}
28
29impl AsRef<[u8; B3Digest::LENGTH]> for B3Digest {
30    fn as_ref(&self) -> &[u8; Self::LENGTH] {
31        &self.0
32    }
33}
34
35impl std::ops::Deref for B3Digest {
36    type Target = [u8; Self::LENGTH];
37
38    fn deref(&self) -> &Self::Target {
39        &self.0
40    }
41}
42
43impl From<B3Digest> for bytes::Bytes {
44    fn from(val: B3Digest) -> Self {
45        Bytes::copy_from_slice(&val.0)
46    }
47}
48
49impl From<blake3::Hash> for B3Digest {
50    fn from(value: blake3::Hash) -> Self {
51        Self(*value.as_bytes())
52    }
53}
54impl From<digest::Output<blake3::Hasher>> for B3Digest {
55    fn from(value: digest::Output<blake3::Hasher>) -> Self {
56        Self(value.into())
57    }
58}
59
60impl TryFrom<&[u8]> for B3Digest {
61    type Error = Error;
62
63    // constructs a [B3Digest] from a &[u8].
64    // Returns an error if the digest has the wrong length.
65    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
66        Ok(Self(
67            value
68                .try_into()
69                .map_err(|_e| Error::InvalidDigestLen(value.len()))?,
70        ))
71    }
72}
73
74impl TryFrom<bytes::Bytes> for B3Digest {
75    type Error = Error;
76
77    fn try_from(value: bytes::Bytes) -> Result<Self, Self::Error> {
78        value[..].try_into()
79    }
80}
81
82impl TryFrom<Vec<u8>> for B3Digest {
83    type Error = Error;
84
85    fn try_from(value: Vec<u8>) -> Result<Self, Self::Error> {
86        value[..].try_into()
87    }
88}
89
90impl From<&[u8; B3Digest::LENGTH]> for B3Digest {
91    fn from(value: &[u8; B3Digest::LENGTH]) -> Self {
92        Self(*value)
93    }
94}
95
96impl From<B3Digest> for [u8; B3Digest::LENGTH] {
97    fn from(value: B3Digest) -> Self {
98        value.0
99    }
100}
101
102impl std::fmt::Display for B3Digest {
103    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
104        f.write_str("blake3-").unwrap();
105        BASE64.encode_write(&self.0, f)
106    }
107}
108
109impl std::fmt::Debug for B3Digest {
110    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
111        f.write_str("blake3-").unwrap();
112        BASE64.encode_write(&self.0, f)
113    }
114}
115
116impl FromStr for B3Digest {
117    type Err = Error;
118
119    fn from_str(s: &str) -> Result<Self, Self::Err> {
120        if !s.starts_with("blake3-") {
121            return Err(Error::InvalidHashType);
122        }
123        let encoded = &s[7..];
124        let decoded = BASE64
125            .decode(encoded.as_bytes())
126            .map_err(|_| Error::InvalidDigestLen(s.len()))?;
127        decoded.as_slice().try_into()
128    }
129}
130
131#[cfg(test)]
132mod test {
133    use crate::B3Digest;
134
135    /// ensures B3Digest::EMPTY actually equals the BLAKE3 digest of an empty slice.
136    #[test]
137    fn empty() {
138        let exp: B3Digest = blake3::hash(b"").as_bytes().into();
139        assert_eq!(exp, B3Digest::EMPTY);
140    }
141}
snix_castore/digests.rs

snix_castore/
digests.rs
