feat: add common interface for hash verification

Author: emilazy

gix-hash/src/lib.rs

@@ -24,6 +24,9 @@ pub use object_id::{decode, ObjectId};
 ///
 pub mod prefix;
 
+///
+pub mod verify;
+
 /// A partial, owned hash possibly identifying an object uniquely, whose non-prefix bytes are zeroed.
 ///
 /// An example would `0000000000000000000000000000000032bd3242`, where `32bd3242` is the prefix,

gix-hash/src/verify.rs

@@ -0,0 +1,27 @@
+use crate::{oid, ObjectId};
+
+/// The error returned by [`oid::verify()`].
+#[derive(Debug, thiserror::Error)]
+#[allow(missing_docs)]
+#[error("Hash was {actual}, but should have been {expected}")]
+pub struct Error {
+    actual: ObjectId,
+    expected: ObjectId,
+}
+
+impl oid {
+    /// Verify that `self` matches the `expected` object ID.
+    ///
+    /// Returns an [`Error`] containing both object IDs if they differ.
+    #[inline]
+    pub fn verify(&self, expected: &oid) -> Result<(), Error> {
+        if self == expected {
+            Ok(())
+        } else {
+            Err(Error {
+                actual: self.to_owned(),
+                expected: expected.to_owned(),
+            })
+        }
+    }
+}