def route.need

mylsm-lsm-store@0.6.0.1 · src/scan/ByteBlockReader.bend:866

import Base
import mylsm-lsm-store@0.6.0.1/src/Fs.bend as Fs
import mylsm-lsm-store@0.6.0.1/src/scan/BlockRoutePolicy.bend as BlockRoutePolicy
import bend-kit-bytes@0.3.2.0/bytes.bend as Bytes

866def route.need(
867  file: File,
868  state: State,
869  +context: RouteContext,
870  key: Bytes.Bytes,
871  +search: BlockRoutePolicy.Search,
872  active: Bool
873) -> IO(RouteState):
874  match context:
875    case RouteContext{_, index_offset, _}:
876      match active:
877        case False{}:
878          IO.pure(RouteState, RouteSelect{Reader{file, state},
879            BlockRoutePolicy.selected_block(search)})
880        case True{}:
881          +mid = route.midpoint(search)
882          do IO<RouteState>:
883            raw : File & Result<&1, &1, U32 & String, Bytes.Bytes> <-
884              Fs.read_at(file, U32.from_nat(Nat.add(index_offset,
885                Nat.add(8n, Nat.mul(mid, 16n)))), 16)
886            return RouteRecordRead{
887              read_at.exact.pair(16, raw), state, context, key, search, mid}