yifan-c commented on code in PR #46:
URL:
https://github.com/apache/cassandra-analytics/pull/46#discussion_r1541824843
##########
cassandra-analytics-core/src/main/java/org/apache/cassandra/spark/utils/XXHash32DigestAlgorithm.java:
##########
@@ -61,7 +61,10 @@ public Digest calculateFileDigest(Path path) throws
IOException
{
hasher.update(buffer, 0, len);
}
- return new XXHash32Digest(Long.toHexString(hasher.getValue()),
SEED);
+ // lz4 library doesn't mask the hash value, so we need to mask it
to
+ // prevent forwarding the negative sign bit when converting to a
long value
+ long hash = hasher.getValue() & 0xffffffffL;
Review Comment:
The comment is not true.
There is no mask required for lz4's implementation since it returns `int`.
Masking is required because our code casts `int` to `long`, and the sign bit
cannot be carried over.
Alternatively, you can just call this w/o masking.
```java
Integer.toHexString(hasher.getValue())
```
And the proof.
```
jshell> int i = -1;
i ==> -1
jshell> Integer.toHexString(i);
$2 ==> "ffffffff"
jshell> long l = i & 0xffffffffL;
l ==> 4294967295
jshell> Long.toHexString(l);
$4 ==> "ffffffff"
```
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