fix(checksum): align multipart CRC64NVME with full object (#2286)

crates/rio/src/checksum.rs

@@ -981,17 +981,17 @@ const CRC64_NVME_POLYNOMIAL: u64 = 0xad93d23594c93659;
 /// GF(2) matrix multiplication
 fn gf2_matrix_times(mat: &[u64], mut vec: u64) -> u64 {
     let mut sum = 0u64;
-    let mut mat_iter = mat.iter();
+    for &m in mat {
+        if vec == 0 {
+            break;
+        }
 
-    while vec != 0 {
-        if vec & 1 != 0
-            && let Some(&m) = mat_iter.next()
-        {
+        if vec & 1 != 0 {
             sum ^= m;
         }
         vec >>= 1;
-        mat_iter.next();
     }
+
     sum
 }
 
@@ -1128,3 +1128,62 @@ fn crc64_combine(poly: u64, crc1: u64, crc2: u64, len2: i64) -> u64 {
     // Return combined crc
     crc1n ^ crc2
 }
+
+#[cfg(test)]
+mod tests {
+    use super::{Checksum, ChecksumType};
+
+    #[test]
+    fn crc64_nvme_add_part_matches_full_object_checksum() {
+        let data = (0..200_000).map(|i| (i % 251) as u8).collect::<Vec<_>>();
+        let split_at = 73_421;
+        let (first, second) = data.split_at(split_at);
+
+        let expected = Checksum::new_from_data(ChecksumType::CRC64_NVME, &data).expect("full checksum");
+        let first_checksum = Checksum::new_from_data(ChecksumType::CRC64_NVME, first).expect("first checksum");
+        let second_checksum = Checksum::new_from_data(ChecksumType::CRC64_NVME, second).expect("second checksum");
+
+        let mut combined = Checksum {
+            checksum_type: ChecksumType::CRC64_NVME,
+            ..Default::default()
+        };
+        combined
+            .add_part(&first_checksum, first.len() as i64)
+            .expect("add first part");
+        combined
+            .add_part(&second_checksum, second.len() as i64)
+            .expect("add second part");
+
+        assert_eq!(combined.encoded, expected.encoded);
+        assert_eq!(combined.raw, expected.raw);
+    }
+
+    #[test]
+    fn crc32c_add_part_matches_full_object_checksum() {
+        let data = (0..32_768).map(|i| (255 - (i % 251)) as u8).collect::<Vec<_>>();
+        let (first, rest) = data.split_at(7_777);
+        let (second, third) = rest.split_at(13_333);
+
+        let expected = Checksum::new_from_data(ChecksumType::CRC32C, &data).expect("full checksum");
+        let first_checksum = Checksum::new_from_data(ChecksumType::CRC32C, first).expect("first checksum");
+        let second_checksum = Checksum::new_from_data(ChecksumType::CRC32C, second).expect("second checksum");
+        let third_checksum = Checksum::new_from_data(ChecksumType::CRC32C, third).expect("third checksum");
+
+        let mut combined = Checksum {
+            checksum_type: ChecksumType::CRC32C,
+            ..Default::default()
+        };
+        combined
+            .add_part(&first_checksum, first.len() as i64)
+            .expect("add first part");
+        combined
+            .add_part(&second_checksum, second.len() as i64)
+            .expect("add second part");
+        combined
+            .add_part(&third_checksum, third.len() as i64)
+            .expect("add third part");
+
+        assert_eq!(combined.encoded, expected.encoded);
+        assert_eq!(combined.raw, expected.raw);
+    }
+}