1pub use crate::msgs::enums::HashAlgorithm;
2
3use alloc::boxed::Box;
4
5/// Describes a single cryptographic hash function.
6///
7/// This interface can do both one-shot and incremental hashing, using
8/// [`Hash::hash()`] and [`Hash::start()`] respectively.
9pub trait Hash: Send + Sync {
10 /// Start an incremental hash computation.
11 fn start(&self) -> Box<dyn Context>;
12
13 /// Return the output of this hash function with input `data`.
14 fn hash(&self, data: &[u8]) -> Output;
15
16 /// The length in bytes of this hash function's output.
17 fn output_len(&self) -> usize;
18
19 /// Which hash function this is, eg, `HashAlgorithm::SHA256`.
20 fn algorithm(&self) -> HashAlgorithm;
21}
22
23/// A hash output, stored as a value.
24pub struct Output {
25 buf: [u8; Self::MAX_LEN],
26 used: usize,
27}
28
29impl Output {
30 /// Build a `hash::Output` from a slice of no more than `Output::MAX_LEN` bytes.
31 pub fn new(bytes: &[u8]) -> Self {
32 let mut output: Output = Self {
33 buf: [0u8; Self::MAX_LEN],
34 used: bytes.len(),
35 };
36 debug_assert!(bytes.len() <= Self::MAX_LEN);
37 output.buf[..bytes.len()].copy_from_slice(src:bytes);
38 output
39 }
40
41 /// Maximum supported hash output size: supports up to SHA512.
42 pub const MAX_LEN: usize = 64;
43}
44
45impl AsRef<[u8]> for Output {
46 fn as_ref(&self) -> &[u8] {
47 &self.buf[..self.used]
48 }
49}
50
51/// How to incrementally compute a hash.
52pub trait Context: Send + Sync {
53 /// Finish the computation, returning the resulting output.
54 ///
55 /// The computation remains valid, and more data can be added later with
56 /// [`Context::update()`].
57 ///
58 /// Compare with [`Context::finish()`] which consumes the computation
59 /// and prevents any further data being added. This can be more efficient
60 /// because it avoids a hash context copy to apply Merkle-Damgård padding
61 /// (if required).
62 fn fork_finish(&self) -> Output;
63
64 /// Fork the computation, producing another context that has the
65 /// same prefix as this one.
66 fn fork(&self) -> Box<dyn Context>;
67
68 /// Terminate and finish the computation, returning the resulting output.
69 ///
70 /// Further data cannot be added after this, because the context is consumed.
71 /// Compare [`Context::fork_finish()`].
72 fn finish(self: Box<Self>) -> Output;
73
74 /// Add `data` to computation.
75 fn update(&mut self, data: &[u8]);
76}
77