From: Patrick Steinhardt <ps@pks.im>
Date: Tue, 28 Oct 2025 09:18:04 GMT
Subject: Re: [PATCH 05/14] rust: add a hash algorithm abstraction
Message-ID: <aQCKTFrmtlp9UEL6@pks.im>
In-Reply-To: <20251027004404.2152927-6-sandals@crustytoothpaste.net>

On Mon, Oct 27, 2025 at 12:43:55AM +0000, brian m. carlson wrote:
> diff --git a/src/hash.rs b/src/hash.rs
> index 0219391820..1b9f07489e 100644
> --- a/src/hash.rs
> +++ b/src/hash.rs
> @@ -19,3 +19,145 @@ pub struct ObjectID {
>      pub hash: [u8; GIT_MAX_RAWSZ],
>      pub algo: u32,
>  }
> +
> +#[allow(dead_code)]
> +impl ObjectID {
> +    pub fn as_slice(&self) -> &[u8] {
> +        match HashAlgorithm::from_u32(self.algo) {
> +            Some(algo) => &self.hash[0..algo.raw_len()],
> +            None => &self.hash,
> +        }
> +    }
> +
> +    pub fn as_mut_slice(&mut self) -> &mut [u8] {
> +        match HashAlgorithm::from_u32(self.algo) {
> +            Some(algo) => &mut self.hash[0..algo.raw_len()],
> +            None => &mut self.hash,
> +        }
> +    }
> +}
> +
> +/// A hash algorithm,
> +#[repr(C)]
> +#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq)]
> +pub enum HashAlgorithm {
> +    SHA1 = 1,
> +    SHA256 = 2,
> +}
> +

Seeing all the `match` statements: we could alternatively implement this
as a trait. This would have the added benefit that we cannot miss
updating any of the functions if we ever were to add another hash
function.

Patrick