-- File: LoopBackPlug.mesa,  Last Edit:
  -- MAS  April 17, 1980  10:55 PM
  -- HGM  October 15, 1979  10:26 PM
-- This module is needed/used only in the funny localOnly mode.

-- Copyright  Xerox Corporation 1979, 1980


DIRECTORY
  InlineDefs: FROM "InlineDefs" USING [COPY],
  CommUtilDefs: FROM "CommUtilDefs" USING [GetEthernetHostNumber],
  StatsDefs: FROM "StatsDefs" USING [StatBump, StatIncr],
  DriverDefs: FROM "DriverDefs" USING [
    doStats, Glitch,
    useCount, firstNetwork, CreateDefaultEthernetDriver,
    GetInputBuffer, AddDeviceToChain, Network, NetworkObject,
    PutOnGlobalDoneQueue, PutOnGlobalInputQueue],
  PupDefs: FROM "PupDefs" USING [GetDoStats],
  BufferDefs: FROM "BufferDefs",
  DriverTypes: FROM "DriverTypes" USING [pupLocalPacket],
  PupTypes: FROM "PupTypes" USING [PupErrorCode, noErrorPupErrorCode];

LoopBackPlug: MONITOR
  IMPORTS InlineDefs, CommUtilDefs, StatsDefs, DriverDefs, PupDefs
  EXPORTS DriverDefs, PupDefs
  SHARES BufferDefs, DriverTypes =
BEGIN OPEN StatsDefs, BufferDefs, DriverDefs;

localEncapsulationOffset: CARDINAL = 4;
localEncapsulationBytes: CARDINAL = 4;

myNetwork: DriverDefs.NetworkObject _ [
  decapsulateBuffer: DecapsulateBuffer,
  encapsulatePup: EncapsulatePup,
  encapsulateRpp: EncapsulateRpp,
  sendBuffer: SendBuffer,
  forwardBuffer: ForwardBuffer,
  activateDriver: ActivateDriver,
  deactivateDriver: DeactivateDriver,
  deleteDriver: DeleteDriver,
  interrupt: DeactivateDriver,  -- No interrupt routine
  device: local,
  alive: TRUE,
  speed: 3000,
  index: ,
  netNumber: 0,
  hostNumber: ,
  next: NIL,
  pupStats: PupStats,
  stats: NIL ];

CommPackageAlreadyActive: PUBLIC ERROR = CODE;
MachineIDTooBigForEthernet: PUBLIC ERROR = CODE;

SetLocalOnly: PUBLIC PROCEDURE [localOnly: BOOLEAN] =
  BEGIN
  -- NB: This won't work in the multi network case.
  IF DriverDefs.useCount#0 THEN DriverDefs.Glitch[CommPackageAlreadyActive];
  DriverDefs.firstNetwork _ NIL;
  IF localOnly THEN [] _ CreateLoopBackNetwork[]
  ELSE [] _ DriverDefs.CreateDefaultEthernetDriver[];
  END;

DecapsulateBuffer: PROCEDURE [b: Buffer] RETURNS [BufferDefs.BufferType] =
  BEGIN
  SELECT b.encapsulation.localType FROM
    DriverTypes.pupLocalPacket => RETURN[pup];
    ENDCASE => RETURN[rejected];
  END;

EncapsulateRpp: PROCEDURE [RppBuffer, PupHostID] = LOOPHOLE[EncapsulatePup];
EncapsulatePup: PROCEDURE [b: PupBuffer, destination: PupHostID] =
  BEGIN
  b.encapsulation _ [ local [
    localSpare1:, localSpare2:, localSpare3:, localSpare4:,
    localHost: b.dest.host,
    localType: DriverTypes.pupLocalPacket ] ];
  b.length _ (b.pupLength+1+localEncapsulationBytes)/2;
  END;

ForwardBuffer: PROCEDURE [b: Buffer] RETURNS [PupTypes.PupErrorCode] =
  BEGIN
  SendBuffer[b];
  RETURN[PupTypes.noErrorPupErrorCode];
  END;

SendBuffer: ENTRY PROCEDURE [b: Buffer] =
  BEGIN
  copy: Buffer;
  b.device _ local;
  IF b.encapsulation.localHost=myNetwork.hostNumber THEN
    BEGIN  -- sending to ourself, copy it over
    copy _ GetInputBuffer[];
    IF copy#NIL THEN
      BEGIN
      copy.device _ local;
      InlineDefs.COPY[
        from: @b.encapsulation+localEncapsulationOffset,
        nwords: b.length,
        to: @copy.encapsulation+localEncapsulationOffset ];
      copy.length _ b.length;
      copy.network _ @myNetwork;
      IF doStats THEN StatIncr[statEtherPacketsLocal];
      IF doStats THEN StatBump[statEtherWordsLocal,b.length];
      END
    ELSE IF doStats THEN StatIncr[statEtherEmptyFreeQueue];
    PutOnGlobalDoneQueue[b];  -- give this one back first
    IF copy#NIL THEN PutOnGlobalInputQueue[copy];
    RETURN
    END;
  PutOnGlobalDoneQueue[b];  -- just throw it away
  END;

CreateLoopBackNetwork: PUBLIC PROCEDURE RETURNS [BOOLEAN] =
  BEGIN
  AddDeviceToChain[@myNetwork,0];
  RETURN[TRUE];
  END;

DeleteDriver: PROCEDURE =
  BEGIN
  END;

ActivateDriver: PROCEDURE =
  BEGIN
  myNetwork.hostNumber _ CommUtilDefs.GetEthernetHostNumber[];
  END;

DeactivateDriver: PROCEDURE =
  BEGIN
  END;

PupStats: PROCEDURE [PupBuffer, Network] RETURNS [BOOLEAN] =
  BEGIN
  RETURN[FALSE];
  END;

-- initialization
[] _ PupDefs.GetDoStats[];  -- Get main PupPackage started
END.  -- LoopBackPlug module(2048)\1682b12B323b17B194b14B63b14B290b13B131b10B871b21B105b12B30b14B93b16B30b8B