QNBSBMN.MOD

IMPLEMENTATION MODULE QNBSBMN;
(*==============================================================
    Version  : 1.00  16 May 1989  C. Lins
    Compiler : TopSpeed Modula-2
    Code Size: R-  bytes
    Component: Monolithic Structures - Queue (Opaque version)
      Non-Priority Balking Sequential Bounded Managed Non-Iterator

    REVISION HISTORY
    v1.00  16 May 1989  C. Lins
      Initial TopSpeed Modula-2 implementation.

    (C) Copyright 1989 Charles A. Lins
==============================================================*)

FROM JPIStorage IMPORT
    (*--Proc*) Allocate, Deallocate;

FROM ErrorHandling IMPORT
    (*--Type*) HandlerProc,
    (*--Proc*) Raise, NullHandler, ExitOnError;

FROM Items IMPORT
    (*--Cons*) NullItem,
    (*--Type*) Item, AssignProc, DisposeProc, CompareProc;

FROM Relations IMPORT
    (*--Type*) Relation;

FROM QEnum IMPORT
    (*--Type*) Operations, Exceptions, ComponentID;

FROM TypeManager IMPORT
    (*--Cons*) NullType,
    (*--Type*) TypeID,
    (*--Proc*) AssignOf, DisposeOf, CompareOf;

    (*--------------------*)


TYPE  ItemsArray   = ARRAY QueueSize OF Item;
TYPE  BoundedQueue = RECORD
        dataID   : TypeID;          (*-- defined data type *)
        size     : QueueSize;       (*-- maximum # of items *)
        rear     : CARDINAL;        (*-- current # of items *)
        items    : ItemsArray;      (*-- array [1..size] of item *)
      END (*-- BoundedQueue *);

TYPE  Queue = POINTER TO BoundedQueue;

    (*--------------------*)


VAR   queueError : Exceptions;
VAR   handlers   : ARRAY Exceptions OF HandlerProc;


PROCEDURE QueueError () : Exceptions (*-- out   *);
BEGIN
  RETURN queueError;
END QueueError;
(*-------------------------*)

PROCEDURE SetHandler (    theError   : Exceptions  (*-- in    *);
                          theHandler : HandlerProc (*-- in    *));
BEGIN
  handlers[theError] := theHandler;
END SetHandler;
(*-------------------------*)

PROCEDURE GetHandler (    theError   : Exceptions  (*-- in    *))
                                     : HandlerProc (*-- out   *);
BEGIN
  RETURN handlers[theError];
END GetHandler;
(*-------------------------*)

PROCEDURE RaiseErrIn (    theRoutine : Operations (*-- in    *);
                          theError   : Exceptions (*-- in    *));
BEGIN
  queueError := theError;
  Raise(ComponentID + ModuleID, theRoutine, theError, handlers[theError]);
END RaiseErrIn;
(*-------------------------*)


    (*--------------------*)

PROCEDURE Create  (    theType  : TypeID    (*-- in    *);
                       theSize  : QueueSize (*-- in    *))
                                : Queue     (*-- out   *);

CONST staticSize = SIZE(BoundedQueue) - SIZE(ItemsArray);
CONST itemSize   = SIZE(Item);

VAR   newQueue : Queue;

BEGIN
  queueError := noerr;
  Allocate(newQueue, staticSize + itemSize * theSize);
  IF (newQueue = NIL) THEN
    RaiseErrIn(create, overflow);
  ELSE
    WITH newQueue^ DO
      dataID   := theType;
      size     := theSize;
      rear     := 0;
    END(*--with*);
  END(*--if*);
  RETURN newQueue;
END Create;
(*-------------------------*)

(*
Destroy lets Clear raise the undefined exception and simply releases
dynamically allocated memory resources for theQueue rear to the system.
MacSystem.Deallocate automatically releases the proper amount of space
originally allocated and alters the pointer to NIL (which is also the
value of the NullQueue). Complexity: O(1).
*)

PROCEDURE Destroy (VAR theQueue : Queue     (*-- inout *));

CONST staticSize = SIZE(BoundedQueue) - SIZE(ItemsArray);
CONST itemSize   = SIZE(Item);

BEGIN
  Clear(theQueue);
  IF (queueError = noerr) THEN
    Deallocate(theQueue, staticSize + itemSize * theQueue^.size);
  END (*--if*);
END Destroy;
(*-------------------------*)

(*
Clear retrieves the item disposal routine for theQueue's data type, if
any, and proceeds to free each item in theQueue.  If theQueue is empty
the loop is not executed as rear will be greater than the minimum
QueueSize.  Lastly, rear is set to ensure theQueue is in the empty state.
Complexity: O(n).
*)

PROCEDURE Clear   (VAR theQueue : Queue     (*-- inout *));

VAR   index : CARDINAL;    (*-- loop index over items *)
      free  : DisposeProc; (*-- item disposal routine *)

BEGIN
  queueError := noerr;
  IF (theQueue # NIL) THEN
    WITH theQueue^ DO
      free := DisposeOf(dataID);
      FOR index := MIN(QueueSize) TO rear DO
        free(items[index]);
      END (*--for*);
      rear := 0;
    END (*--with*);
  ELSE
    RaiseErrIn(clear, undefined);
  END (*--if*);
END Clear;
(*-------------------------*)

(*
Assign duplicates the items of theQueue to the target queue, toQueue. An
undefined source queue raised an exception and leaves the target unchanged.
If the target queue is undefined, it is created with the same size and
data type attributes of the source; otherwise the target queue is
cleared of its presnet contents and its data type is altered to reflect
that of the source.  If the target queue is capable of containing all
of the items present in the source, Assign simply copies each item from
the source to the target afterwards updating the target's rear value.
Complexity: O(n).
*)

PROCEDURE Assign  (    theQueue : Queue     (*-- in    *);
                   VAR toQueue  : Queue     (*-- inout *));

VAR   index      : CARDINAL;   (*-- loop index over items *)
      assignment : AssignProc; (*-- item assignment routine *)

BEGIN
  queueError := noerr;
  IF (theQueue = NIL) THEN
    RaiseErrIn(assign, undefined);
  ELSIF (theQueue # toQueue) THEN
    IF (toQueue = NIL) THEN
      WITH theQueue^ DO
        toQueue := Create(dataID, size);
      END (*--with*);
    ELSIF (theQueue^.rear <= toQueue^.size) THEN
      Clear(toQueue);
      WITH theQueue^ DO
        toQueue^.dataID   := dataID;
      END (*--with*);
    ELSE
      RaiseErrIn(assign, overflow);
    END (*--if*);
    IF (queueError = noerr) THEN
      WITH theQueue^ DO
        assignment := AssignOf(dataID);
        FOR index := MIN(QueueSize) TO rear DO
          toQueue^.items[index] := assignment(items[index]);
        END (*--for*);
        toQueue^.rear := rear;
      END (*--with*);
    END (*--if*);
  END (*--if*);
END Assign;
(*-------------------------*)

(*
Arrive adds theItem to the end of the queue.
When the rear of theQueue
is already at its maximum allowed size the exception overflow is raised
and theQueue remains unchanged.  Likewise, given an undefined queue
raises the exception of the same name. Complexity: O(1).
*)

PROCEDURE Arrive  (VAR theQueue : Queue     (*-- inout *);
                       theItem  : Item      (*-- in    *));

VAR   index : CARDINAL; (*-- loop index over items *)

BEGIN
  queueError := noerr;
  IF (theQueue = NIL) THEN
    RaiseErrIn(arrive, undefined);
  ELSE
    WITH theQueue^ DO
      IF (rear < size) THEN
        INC(rear);
        items[rear] := theItem;
      ELSE
        RaiseErrIn(arrive, overflow);
      END (*--if*);
    END (*--with*);
  END (*--if*);
END Arrive;
(*-------------------------*)

(*
Depart removes theItem at the front of theQueue by shifting all items
down one position in the items array and deducting one from the rear
index.  Before overwriting the item being removed, it's value is
freed via the disposal routine of theQueue's data type.  If theQueue
is empty on entry to Depart the underflow exception is raised and
theQueue is not changed.  When theQueue is not defined, the undefined
exception is raised. Complexity: O(n).
*)

PROCEDURE Depart  (VAR theQueue : Queue     (*-- inout *));

VAR   index : CARDINAL;    (*-- loop index over items *)
      free  : DisposeProc; (*-- item disposal routine *)

BEGIN
  queueError := noerr;
  IF (theQueue = NIL) THEN
    RaiseErrIn(depart, undefined);
  ELSE
    WITH theQueue^ DO
      IF (rear = 0) THEN
        RaiseErrIn(depart, underflow);
      ELSE
        free := DisposeOf(dataID);
        free(items[MIN(QueueSize)]);
        FOR index := MIN(QueueSize) + 1 TO rear DO
          items[index - 1] := items[index];
        END (*--for*);
        DEC(rear);
      END (*--if*);
    END (*--with*);
  END (*--if*);
END Depart;
(*-------------------------*)

(*
Leave removes theItem from the Queue regardless of its position within
the queue.  Complexity: O(n).
*)

PROCEDURE Leave   (VAR theQueue : Queue     (*-- inout *);
                       theItem  : Item      (*-- in    *));

VAR   index : CARDINAL;    (*-- loop index over items *)
      free  : DisposeProc; (*-- item disposal routine *)

BEGIN
  queueError := noerr;
  IF (theQueue = NIL) THEN
    RaiseErrIn(leave, undefined);
  ELSE
    WITH theQueue^ DO
      IF (rear = 0) THEN
        RaiseErrIn(leave, underflow);
      ELSE
        free := DisposeOf(dataID);
        index := MIN(QueueSize);
        WHILE (index <= rear) & (items[index] # theItem) DO
          INC(index);
        END (*-- while*);
        IF (index <= rear) THEN
          free(items[index]);
          FOR index := index + 1 TO rear DO
            items[index - 1] := items[index];
          END (*--for*);
          DEC(rear);
        ELSE
          RaiseErrIn(leave, notfound);
        END (*--if*);
      END (*--if*);
    END (*--with*);
  END (*--if*);
END Leave;
(*-------------------------*)


(*
12.2.4 Selectors

IsDefined verifies to the best of its ability whether theQueue has been
created and is still an active object. Complexity: O(1).
*)

PROCEDURE IsDefined (    theQueue : Queue    (*-- in    *))
                                  : BOOLEAN  (*-- out   *);
BEGIN
  RETURN theQueue # NIL;
END IsDefined;
(*-------------------------*)

(*
IsEmpty returns True if theQueue is in the empty state, as indicated by
the rear being zero, and False otherwise.  As per the specification
(section 9.4) undefined queues are considered empty. Complexity: O(1).
*)

PROCEDURE IsEmpty   (    theQueue : Queue    (*-- in    *))
                                  : BOOLEAN  (*-- out   *);
BEGIN
  queueError := noerr;
  IF (theQueue # NIL) THEN
    RETURN (theQueue^.rear = 0);
  END (*--if*);
  RaiseErrIn(isempty, undefined);
  RETURN TRUE;
END IsEmpty;
(*-------------------------*)

(*
IsEqual compares the left and right queues for equality, which in this
context means they contain the same items and the same data type ID. The
defined size of the queues is not relevant for the equality test.  Both
queues must be defined and have the same data type ID; if they don not,
then the exceptions undefined and typeerror are raised, respectively.
Obviously, queues of different lengths (indicated by the value of rear)
cannot be equal since there would be at least one item different between
them.  The algorithm simply loops over each of the items in both queues
returning false immediately upon encountering an inequality, and returning
true if and only if every item is the same between them. Complexity: O(n).
*)

PROCEDURE IsEqual   (    left     : Queue    (*-- in    *);
                         right    : Queue    (*-- in    *))
                                  : BOOLEAN  (*-- out   *);

VAR   index : CARDINAL; (*-- loop index over items *)
      compare : CompareProc;    (*-- item comparison routine *)

BEGIN
  queueError := noerr;
  IF (left = NIL) OR (right = NIL) THEN
    RaiseErrIn(isequal, undefined);
  ELSIF (left^.dataID # right^.dataID) THEN
    RaiseErrIn(isequal, typeerror);
  ELSIF (left^.rear = right^.rear) THEN
    WITH left^ DO
      compare := CompareOf(dataID);
      FOR index := MIN(QueueSize) TO rear DO
        IF compare(items[index], right^.items[index]) # equal THEN
          RETURN FALSE;
        END (*--if*);
      END (*--for*);
      RETURN TRUE;
    END (*--with*);
  END (*--if*);
  RETURN FALSE;
END IsEqual;
(*-------------------------*)

(*
LengthOf simply returns the rear index into the items array which is
also the length of theQueue. Complexity: O(1).
*)

PROCEDURE LengthOf  (    theQueue : Queue    (*-- in    *))
                                  : CARDINAL (*-- out   *);
BEGIN
  queueError := noerr;
  IF (theQueue # NIL) THEN
    RETURN theQueue^.rear;
  END (*--if*);
  RaiseErrIn(lengthof, undefined);
  RETURN 0;
END LengthOf;
(*-------------------------*)

(*
SizeOf and TypeOf simply return the size and dataID for the given queue.
Undefined queues, as always, raise the undefined exception and return
reasonable values (zero and the NullType, respectively). The complexity
of both routines is O(1).
*)

PROCEDURE SizeOf    (    theQueue : Queue    (*-- in    *))
                                  : CARDINAL (*-- out   *);
BEGIN
  queueError := noerr;
  IF (theQueue # NIL) THEN
    RETURN theQueue^.size;
  END (*--if*);
  RaiseErrIn(sizeof, undefined);
  RETURN 0;
END SizeOf;
(*-------------------------*)

PROCEDURE TypeOf    (    theQueue : Queue    (*-- in    *))
                                  : TypeID   (*-- out   *);
BEGIN
  queueError := noerr;
  IF (theQueue # NIL) THEN
    RETURN theQueue^.dataID;
  END (*--if*);
  RaiseErrIn(typeof, undefined);
  RETURN NullType;
END TypeOf;
(*-------------------------*)

(*
FrontOf returns the value of the item that is at the front of theQueue or
the NullItem if theQueue is undefined or is empty. Complexity: O(1).
*)

PROCEDURE FrontOf   (    theQueue : Queue    (*-- in    *))
                                  : Item     (*-- out   *);
BEGIN
  queueError := noerr;
  IF (theQueue = NIL) THEN
    RaiseErrIn(frontof, undefined);
  ELSIF (theQueue^.rear = 0) THEN
    RaiseErrIn(frontof, underflow);
  ELSE
    RETURN theQueue^.items[MIN(QueueSize)];
  END (*--if*);
  RETURN NullItem;
END FrontOf;
(*-------------------------*)

(*
PositionOf returns the number of positions from the given item to the
front of the queue. If theItem is not present in theQueue then zero
is returned. Complexity O(n).
*)

PROCEDURE PositionOf (    theQueue: Queue    (*-- in    *);
                          theItem : Item     (*-- in    *))
                                  : CARDINAL (*-- out   *);

VAR   index : CARDINAL; (*-- loop index over items *)

BEGIN
  queueError := noerr;
  IF (theQueue = NIL) THEN
    RaiseErrIn(positionof, undefined);
  ELSE
    WITH theQueue^ DO
      FOR index := MIN(QueueSize) TO rear DO
        IF (theItem = items[index]) THEN
          RETURN index;
        END (*--if*);
      END (*--for*);
    END (*--with*);
  END (*--if*);
  RETURN 0;
END PositionOf;
(*-------------------------*)


(*
Module Initialization
*)

BEGIN
  FOR queueError := MIN(Exceptions) TO MAX(Exceptions) DO
    SetHandler(queueError, ExitOnError);
  END (*--for*);
  SetHandler(noerr, NullHandler);
  queueError := noerr;
END QNBSBMN.