feat(tvix/store/digests): use bytes::Bytes instead of Vec<u8>

This will save us some copies, because a clone will simply create an
additional pointer to the same data.

Change-Id: I017a5d6b4c85a861b5541ebad2858ad4fbf8e8fa
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8978
Reviewed-by: raitobezarius <tvl@lahfa.xyz>
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/store/src/digests.rs

@@ -1,10 +1,9 @@
+use bytes::Bytes;
 use data_encoding::BASE64;
 use thiserror::Error;
 
-// FUTUREWORK: make generic
-
 #[derive(PartialEq, Eq, Hash, Debug)]
-pub struct B3Digest(Vec<u8>);
+pub struct B3Digest(Bytes);
 
 // TODO: allow converting these errors to crate::Error
 #[derive(Error, Debug)]
@@ -14,25 +13,49 @@ pub enum Error {
 }
 
 impl B3Digest {
-    // constructs a [B3Digest] from a [Vec<u8>].
-    // Returns an error if the digest has the wrong length.
-    pub fn from_vec(value: Vec<u8>) -> Result<Self, Error> {
-        if value.len() != 32 {
-            Err(Error::InvalidDigestLen(value.len()))
-        } else {
-            Ok(Self(value))
-        }
-    }
-
     // returns a copy of the inner [Vec<u8>].
     pub fn to_vec(&self) -> Vec<u8> {
         self.0.to_vec()
     }
 }
 
+impl From<B3Digest> for bytes::Bytes {
+    fn from(val: B3Digest) -> Self {
+        val.0
+    }
+}
+
+impl TryFrom<Vec<u8>> for B3Digest {
+    type Error = Error;
+
+    // constructs a [B3Digest] from a [Vec<u8>].
+    // Returns an error if the digest has the wrong length.
+    fn try_from(value: Vec<u8>) -> Result<Self, Self::Error> {
+        if value.len() != 32 {
+            Err(Error::InvalidDigestLen(value.len()))
+        } else {
+            Ok(Self(value.into()))
+        }
+    }
+}
+
+impl TryFrom<bytes::Bytes> for B3Digest {
+    type Error = Error;
+
+    // constructs a [B3Digest] from a [bytes::Bytes].
+    // Returns an error if the digest has the wrong length.
+    fn try_from(value: bytes::Bytes) -> Result<Self, Self::Error> {
+        if value.len() != 32 {
+            Err(Error::InvalidDigestLen(value.len()))
+        } else {
+            Ok(Self(value))
+        }
+    }
+}
+
 impl From<&[u8; 32]> for B3Digest {
     fn from(value: &[u8; 32]) -> Self {
-        Self(value.to_vec())
+        Self(value.to_vec().into())
     }
 }
 
@@ -44,6 +67,6 @@ impl Clone for B3Digest {
 
 impl std::fmt::Display for B3Digest {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "b3:{}", BASE64.encode(self.0.as_slice()))
+        write!(f, "b3:{}", BASE64.encode(&self.0))
     }
 }