Function producer_snapshot_replay_start 

pub fn producer_snapshot_replay_start(
    range: ProducerReloadRange,
    snapshot: Option<i64>,
) -> Option<i64>

Select the replay cursor after a reload loaded snapshot, or none.

Kafka’s UnifiedLog.rebuildProducerState replays each local segment from max(segment.baseOffset, mapEndOffset, logStartOffset) (see kafka_replay_start). The range must be nonnegative and ordered, with the local start at or below the log end, and a loaded snapshot must be one the reload keeps; anything else is rejected as corrupt.

The cursor can land inside a batch when a trim did. Kafka’s LogSegment.read(startOffset, ..) then starts from the batch that holds the cursor, and replaying that whole batch is the host’s job.