Trait Source

Source

pub trait Source {
    // Required methods
    fn read_at(&self, offset: u64, buf: &mut [u8]) -> Result<()>;
    fn len(&self) -> Result<u64>;

    // Provided methods
    fn is_empty(&self) -> Result<bool> { ... }
    fn accounts_for_wal(&self) -> bool { ... }
}

Required Methods§

Source

fn read_at(&self, offset: u64, buf: &mut [u8]) -> Result<()>

Read exactly buf.len() bytes at offset. Reading past the end is an error; short reads are never returned.

Source

fn len(&self) -> Result<u64>

Size in bytes.

Provided Methods§

Source

fn is_empty(&self) -> Result<bool>

Source

fn accounts_for_wal(&self) -> bool

Whether this source has already accounted for a write-ahead log.

A wal mode database is only complete in its main file once the log has been checkpointed into it, and bytes alone cannot say whether that happened. A source that knows, because it looked next to the file or because it reads the log itself, says so here; everything else stays conservative and a wal mode database read through it is refused rather than silently truncated to an older version.