Struct Wal 

pub struct Wal { /* private fields */ }

Append-only write-ahead log.

Implementations

impl Wal

pub fn open(dir_path: &Path) -> MenteResult<Self>

Open or create a WAL file at dir_path/wal.log.

pub fn lock_exclusive(&self) -> MenteResult<()>

Acquire a blocking exclusive file lock on the WAL file.

Uses flock(2) (via fs2) which works across processes on the same host. Blocks until the lock is available — callers should hold it only for the duration of append + fsync.

pub fn unlock(&self) -> MenteResult<()>

Release the file lock on the WAL file.

pub fn reload_lsn(&mut self) -> MenteResult<()>

Re-read the WAL file to find the highest LSN, updating next_lsn. Must be called under flock to see writes from other processes.

Fast path: reads each entry’s raw payload and CRC-validates it, but skips the expensive LZ4 decompression. Only extracts the LSN (first 8 bytes of each payload).

pub fn append( &mut self, entry_type: WalEntryType, page_id: u64, data: &[u8], ) -> MenteResult<Lsn>

Append an entry to the WAL and return its LSN.

pub fn sync(&mut self) -> MenteResult<()>

Flush the WAL to durable storage (fdatasync).

pub fn iterate(&mut self) -> MenteResult<Vec<WalEntry>>

Read all valid entries from the WAL for recovery.

pub fn truncate(&mut self, before_lsn: Lsn) -> MenteResult<()>

Truncate all entries with LSN less than before_lsn.

Uses atomic write-to-temp-then-rename to avoid data loss on crash.

pub fn next_lsn(&self) -> Lsn

Current next LSN (useful for external callers).

pub fn file_size(&self) -> u64

Returns the current WAL file size in bytes.