refactor(nix-compat) Make nixhash_* mods hierarchical

They can go under `nixhash`

Change-Id: Ia15835c57130b66d58f5df80ae9595dceee00941
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8408
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/nix-compat/src/nixhash/algos.rs

@@ -0,0 +1,39 @@
+use std::fmt::Display;
+
+use serde::{Deserialize, Serialize};
+
+use crate::nixhash::Error;
+
+/// This are the hash algorithms supported by cppnix.
+#[derive(Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
+pub enum HashAlgo {
+    Md5,
+    Sha1,
+    Sha256,
+    Sha512,
+}
+
+impl Display for HashAlgo {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match &self {
+            HashAlgo::Md5 => write!(f, "md5"),
+            HashAlgo::Sha1 => write!(f, "sha1"),
+            HashAlgo::Sha256 => write!(f, "sha256"),
+            HashAlgo::Sha512 => write!(f, "sha512"),
+        }
+    }
+}
+
+impl TryFrom<&str> for HashAlgo {
+    type Error = Error;
+
+    fn try_from(algo_str: &str) -> Result<Self, Self::Error> {
+        match algo_str {
+            "md5" => Ok(Self::Md5),
+            "sha1" => Ok(Self::Sha1),
+            "sha256" => Ok(Self::Sha256),
+            "sha512" => Ok(Self::Sha512),
+            _ => Err(Error::InvalidAlgo(algo_str.to_string())),
+        }
+    }
+}