Struct MmapWalReader 

pub struct MmapWalReader { /* private fields */ }

Memory-mapped WAL segment reader.

Opens a sealed WAL segment file via mmap and provides zero-copy iteration over records. The mmap’d region is read-only and the kernel manages page residency — no application-level memory pinning.

Implementations

impl MmapWalReader

pub fn open(path: &Path, keys: Option<&KeyRing>) -> Result<Self>

Open a WAL segment file for mmap’d replay.

Every record is decrypted on the way out: what the caller receives never has ENCRYPTED_FLAG set, and its checksum verifies against the plaintext. keys must be the key ring the segment was written under, or None for a segment that was never encrypted — an encrypted record met with no key is WalError::EncryptedRecordWithoutKey, never ciphertext handed to the caller.

pub fn open_raw(path: &Path) -> Result<Self>

Open a WAL segment file for structural scanning only.

Payloads may be ciphertext. Records come out exactly as they are on disk, ENCRYPTED_FLAG and all. Use it only for code that reads record framing and never the payload; replay must use Self::open.

A leading WALP preamble is skipped so iteration begins at the first real record; segments written without encryption have none and start at offset 0.

pub fn segment_preamble(&self) -> Option<&SegmentPreamble>

The preamble read from this segment file, if present.

Returns None for unencrypted segments (no preamble written).

pub fn stop_reason(&self) -> Option<StopReason>

Why iteration stopped, or None while records are still being read.

Feed this to crate::torn_tail::verify_committed_prefix to tell an unfsynced tail apart from a hole with committed records behind it.

pub fn madvise_state(&self) -> Option<c_int>

The madvise hint applied to the mapped segment (if any).

pub fn release_pages(&self)

Hint to the kernel that pages for this segment can be dropped from cache. Call this after a segment has been iterated end-to-end.

pub fn next_record(&mut self) -> Result<Option<WalRecord>>

Read the next record from the mmap’d region.

Returns None at EOF or at the first corruption point. Returns Err for a format version this build cannot read at the segment’s first record, and the caller must stop at that Err. Header parsing avoids extra copies, but the payload is copied out of the mmap’d region into an owned Vec<u8> on WalRecord: records must outlive the reader (they cross thread boundaries in parallel replay and get mutated in place during decryption), which a borrow of the mapping cannot support.

pub fn records(self) -> MmapRecordIter

Iterator over all valid records in the mmap’d segment.

pub fn offset(&self) -> usize

Current read offset.

pub fn len(&self) -> usize

Total size of the mmap’d region.

pub fn is_empty(&self) -> bool

Whether the mmap’d region is empty.