Files
rustfs/crates/ecstore/src
houseme d715cb5c34 refactor(ecstore): single-source the bitrot read/verify path (backlog#1159) (#4697)
P-A (`read_appending`) and P-C (the in-memory fast path) each copied the
hashed-read logic, so `BitrotReader` ended up with the hash verification, the
short-read error, and the scratch-buffer fill written three times across
`read` and `read_appending`'s two branches. That is patch-on-patch: a change
to the bitrot contract would have to be made in three places and kept in
sync by hand.

Collapse the duplication onto three single-source pieces:
- `split_and_verify` — a free function that splits `[hash][data]`, verifies
  (unless skip_verify), and returns the data slice plus the hash time. Free
  rather than a method so it can run while `self` is borrowed for the block.
- `read_scratch_block` — the single-pass fill of `self.buf` with the
  short-read-to-UnexpectedEof contract.
- `short_shard_read` / `begin_read` — the shared error and preamble.

`read` and `read_appending` now differ only in what they must: how the block
is acquired (caller's slice vs `try_take_block` vs scratch fill) and where the
verified shard lands (`copy_from_slice` vs `extend_from_slice`).

This also fixes a latent inconsistency the duplication hid: the old `read`
did `copy_from_slice` *before* verifying, so on a hash mismatch it left the
corrupt bytes in the caller's buffer before returning the error, while
`read_appending` verified first. Both now verify before writing, so a shard
that fails the hash never reaches the caller's buffer on either method — the
stronger of the two behaviors.

Net -19 lines; behavior otherwise unchanged. Verified: `erasure::` 215
passed, 0 failed (including the fast-path equivalence and corrupt-shard tests,
and the existing `test_bitrot_read_hash_mismatch`); clippy --all-targets
-D warnings clean.

Co-authored-by: heihutu <heihutu@gmail.com>
2026-07-10 18:08:07 +00:00
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