ludic/docs/language/networking/fn-serialize.md

id	name	category	kind	tokens	sig	tip	order
fn-serialize	serialize	networking	builtin	serialize	serialize(target, buf) -> int	Pack a model instance's @Sync fields into a buffer; returns bytes written.	50

serialize writes the replicated state of a model instance into buf and returns how many bytes it wrote. It is compiler-generated from the schema: it copies exactly the fields that are both @Sync-marked and participating in that instance's model, tightly packed in member-then-field order, and nothing else. This is the dispatcher over the per-model codecs, so it works for any spawned model whose fields sync. Use it to snapshot state before shipping it with net_send or before a rollback; the inverse is apply, which reads back the identical layout, and sync_size gives the byte count up front so you can size a buffer.

Parameters:

• target — the model instance (an entity) whose synced fields are read
• buf — the destination buffer the packed bytes are written into

program SnapshotPlayer {
  @Sync property Position { column: int = 0, row: int = 0 }
  property Health { @Sync current: int = 0, maximum: int = 0 }
  @Owned model Player { @Sync Position, @Sync Health }

  entry {
    spawn Player { Position { column: 3, row: 4 }, Health { current: 50, maximum: 100 } }
    for (Position, Health) in query [Position, Health, {Player}] {
      let player_id = self()
      let snapshot_buffer = bytes(64)
      let byte_count = serialize(player_id, snapshot_buffer)     # pack column, row, current
      print(byte_count)                                          # 12 = Position(8) + Health.current(4)
    }
  }
}