add Hasher::count

src/lib.rs

@@ -1301,6 +1301,11 @@ impl Hasher {
     pub fn finalize_xof(&self) -> OutputReader {
         OutputReader::new(self.final_output())
     }
+
+    /// Return the total number of bytes hashed so far.
+    pub fn count(&self) -> u64 {
+        self.chunk_state.chunk_counter * CHUNK_LEN as u64 + self.chunk_state.len() as u64
+    }
 }
 
 // Don't derive(Debug), because the state may be secret.

test_vectors/src/lib.rs

@@ -240,26 +240,29 @@ mod tests {
     ) {
         let mut out = vec![0; expected_hash.len()];
         let mut hasher = blake3::Hasher::new();
-        for &b in input {
-            hasher.update(&[b]);
+        for i in 0..input.len() {
+            hasher.update(&[input[i]]);
+            assert_eq!(i as u64 + 1, hasher.count());
         }
         hasher.finalize_xof().fill(&mut out);
         assert_eq!(expected_hash, &out[..]);
         assert_eq!(&expected_hash[..32], hasher.finalize().as_bytes());
 
         let mut out = vec![0; expected_keyed_hash.len()];
         let mut hasher = blake3::Hasher::new_keyed(key);
-        for &b in input {
-            hasher.update(&[b]);
+        for i in 0..input.len() {
+            hasher.update(&[input[i]]);
+            assert_eq!(i as u64 + 1, hasher.count());
         }
         hasher.finalize_xof().fill(&mut out);
         assert_eq!(expected_keyed_hash, &out[..]);
         assert_eq!(&expected_keyed_hash[..32], hasher.finalize().as_bytes());
 
         let mut out = vec![0; expected_derive_key.len()];
         let mut hasher = blake3::Hasher::new_derive_key(TEST_CONTEXT);
-        for &b in input {
-            hasher.update(&[b]);
+        for i in 0..input.len() {
+            hasher.update(&[input[i]]);
+            assert_eq!(i as u64 + 1, hasher.count());
         }
         hasher.finalize_xof().fill(&mut out);
         assert_eq!(expected_derive_key, &out[..]);