Struct FileLedger 

pub struct FileLedger { /* private fields */ }

The file ledger: the position lives in a file, every update holds an exclusive lock on a sibling lock file across its read and its record, and a record is written to a temporary file, synced, renamed over the ledger and the directory synced, so a crash leaves the old position or the new one and a restart resumes past every byte ever handed out. A missing ledger is a fresh pad; a ledger of any other shape, or one that cannot be read, is an error.

Implementations

impl FileLedger

pub fn new(path: impl Into<PathBuf>) -> Self

A ledger kept at path (created on its first record).

pub fn beside(pad: &Path, role: Role) -> Self

The ledger a with pad "<pad>" as <role> session keeps beside its pad.

pub fn path(&self) -> &Path

Where the ledger is kept.

Trait Implementations

impl PadLedgerStore for FileLedger

Available on non-WebAssembly only.

fn update( &self, change: &mut dyn FnMut(&mut PadLedger) -> bool, ) -> Result<PadLedger, LedgerError>

Read the ledger, let change change it, and record the change durably before returning, all under one exclusive hold: no other holder of this ledger reads it between the read and the record. change answers false to leave the ledger as it was. Returns the ledger as it now stands.