Bucket.keyEquals() may throw an underflow exception

[artemananiev]

Here is an example:

2025-07-11 20:09:53.121 ERROR 161  DispatchProcessor - Possibly CATASTROPHIC failure - exception thrown while handling dispatch
java.nio.BufferUnderflowException
        at com.hedera.pbj.runtime.io.buffer.Bytes.getByte(Bytes.java:511)
        at com.swirlds.merkledb.files.hashmap.Bucket.keyEquals(Bucket.java:488)
        at com.swirlds.merkledb.files.hashmap.Bucket.findEntry(Bucket.java:465)
        at com.swirlds.merkledb.files.hashmap.Bucket.findValue(Bucket.java:188)
        at com.swirlds.merkledb.files.hashmap.HalfDiskHashMap.get(HalfDiskHashMap.java:875)
        ...

Bucket.keyEquals() is very straightforward:

    private boolean keyEquals(final long pos, final int size, final Bytes key) {
        for (int i = 0; i < size; i++) {
            if (bucketData.getByte(pos + i) != key.getByte(i)) {
                return false;
            }
        }
        return true;
    }

This method checks if a bucket entry at the given pos matches the given key. Entry hash code is the same as key hash code, but entry may be longer than the key. In this case, the loop above throws a buffer underflow exception.