# Test Case: Metabox shared xattr with nonzero base

**Test ID**: TC134-metabox-shared-nonzero-base
**Fixture**: `metabox-plain.erofs`

## Objective

Verify that metabox shared IDs are relative to the nonzero
`xattr_blkaddr << blkszbits`. Require manifest fields `xattr_blkaddr=1`,
carrier xattr base 4096, shared record IDs/offsets, and bit-63 inode NIDs.

## Manual steps

```sh
getextattr -qq -x user metaboxshared /mnt/repo22-g4/metabox-a
getextattr -qq -x user metaboxshared /mnt/repo22-g4/metabox-b
sha256 -q /mnt/repo22-g4/metabox-a /mnt/repo22-g4/metabox-b
stat -f 'inode=%i size=%z' /mnt/repo22-g4/metabox-a \
  /mnt/repo22-g4/metabox-b
```

## Expected results

Both values are `nonzero-base`; data hashes match source and inode numbers
retain bit 63. A read from logical offset `shared_id * 4` must not occur.
Clean up.
