Struct StorageWriteAheadBuffer 

pub struct StorageWriteAheadBuffer {
    pub entries: Vec<BufferedEntry>,
    pub config: BufferConfig,
    pub next_seq: u64,
    pub total_buffered_bytes: u64,
}

In-memory write-ahead buffer with sequence-numbered entries.

Incoming WriteOps are appended with monotonically increasing sequence numbers. The buffer tracks total payload bytes and the age of the oldest unflushed entry so that callers can decide when to flush.

After a flush the entries remain in entries (marked flushed = true) until trim_flushed is called, enabling crash-recovery replay via replay_from.

Fields

entries: Vec<BufferedEntry>

All entries in arrival order.

config: BufferConfig

Configuration controlling flush thresholds.

next_seq: u64

Next sequence number to assign.

total_buffered_bytes: u64

Running total of size_bytes for unflushed Put ops.

Implementations

impl StorageWriteAheadBuffer

pub fn new(config: BufferConfig) -> Self

Create a new, empty buffer with the supplied configuration.

pub fn write(&mut self, op: WriteOp, now_secs: u64) -> u64

Stage op in the buffer and return the assigned sequence number.

• Put ops increment total_buffered_bytes by their size_bytes.
• Delete and Update ops do not affect the byte counter.

pub fn should_flush(&self, now_secs: u64) -> bool

Returns true if any flush threshold has been reached.

Triggers when:

• the number of unflushed entries ≥ max_buffered_entries, or
• total_buffered_bytes ≥ max_buffered_bytes, or
• the oldest unflushed entry’s age ≥ flush_interval_secs.

pub fn flush(&mut self, _now_secs: u64) -> FlushResult

Mark every unflushed entry as flushed and return a FlushResult.

After this call total_buffered_bytes is reset to 0. Flushed entries are retained in entries until trim_flushed is called.

pub fn pending_entries(&self) -> Vec<&BufferedEntry>

Returns references to all entries that have not yet been flushed, in arrival order.

pub fn replay_from(&self, seq: u64) -> Vec<&BufferedEntry>

Returns references to all entries whose sequence number is ≥ seq, regardless of flushed state. Useful for crash-recovery replay.

pub fn trim_flushed(&mut self)

Remove all entries that have been flushed, freeing memory.

After this call, replay_from will only see entries that have not yet been flushed.

pub fn stats(&self) -> (usize, u64)

Returns (total_entry_count, unflushed_entry_count).