Implement digest::DynDigest for internal Sha512

Cargo.toml

@@ -15,6 +15,7 @@ cosey = { version = "0.3.0", optional = true }
 subtle = { version = "2.4.0", default-features = false }
 zeroize = { version = "1.2.0", default-features = false }
 ed25519 = { version = "1.3.0", default-features = false }
+digest = { version = "0.10", default-features = false }
 
 [dev-dependencies]
 hex = "0.4.2"

src/hash.rs

@@ -270,6 +270,10 @@ impl Sha512 {
     // }
 
     pub fn finalize(mut self) -> Digest {
+        self.finalize_borrow()
+    }
+
+    fn finalize_borrow(&mut self) -> Digest {
         // generate padding (can be 1 or 2 blocks of 128 bytes)
         let mut padding: [u8; 256] = [0u8; 256];
         let padding_length = match self.unprocessed < 112 {
@@ -296,3 +300,34 @@ impl Sha512 {
         self.digest
     }
 }
+
+impl digest::DynDigest for Sha512 {
+    fn update(&mut self, data: &[u8]) {
+        self.update(data)
+    }
+
+    fn finalize_into(self, buf: &mut [u8]) -> Result<(), digest::InvalidBufferSize> {
+        if buf.len() < SHA512_LENGTH {
+            return Err(digest::InvalidBufferSize);
+        }
+        buf.copy_from_slice(&self.finalize());
+        Ok(())
+    }
+
+    fn finalize_into_reset(&mut self, buf: &mut [u8]) -> Result<(), digest::InvalidBufferSize> {
+        if buf.len() < SHA512_LENGTH {
+            return Err(digest::InvalidBufferSize);
+        }
+        buf.copy_from_slice(&self.finalize_borrow());
+        self.reset();
+        Ok(())
+    }
+
+    fn reset(&mut self) {
+        *self = Sha512::new()
+    }
+
+    fn output_size(&self) -> usize {
+        SHA512_LENGTH
+    }
+}