[@DEFINITION MODULE module;

(* Generic Queue Template *)

(* ---------------------------------------------------------------------------

 * This template is expanded by the M 2 R 10? template engine utility. Expansion
 * can be invoked from within a compiling source file using the MAKE pragma:
 * <* MAKE = "m2te Queue module:'Foo Queue?' component:'Foo Record?'" *>
 * IMPORT Foo Queue?;
 * ------------------------------------------------------------------------ *)

FROM Collections IMPORT Capacity, Status;

(* ---------------------------------------------------------------------------

 * Default queue size
 * ------------------------------------------------------------------------ *)

    defaultCapacity = 256;  (* 256 entries *)

(* ---------------------------------------------------------------------------

 * Maximum queue size
 * ------------------------------------------------------------------------ *)

    maximumCapacity = 1024*1024*1024;  (* more than 1 billion entries *)

(* ---------------------------------------------------------------------------

 * Synonyms for status codes
 * ------------------------------------------------------------------------ *)

    invalidQueue = invalidCollection;
    queueEmpty = collectionEmpty;
    queueFull = collectionFull;

(* ---------------------------------------------------------------------------

 * Opaque handle type:  module
 * ------------------------------------------------------------------------ *)

    module = OPAQUE;

    Value Type? = component;

(* ---------------------------------------------------------------------------

 * function:  module.new ( size, status )
 * ---------------------------------------------------------------------------
 *
 * Creates and returns  a new queue object  with a storage capacity of <size>.
 * If zero is passed in for <size>,  then the new queue object will be created
 * with a capacity of  module.defaultQueueSize.
 * Returns NIL if the queue object could not be created.
 *
 * The status of the operation is passed back in <status>. *)

PROCEDURE new ( initialSize : Capacity; VAR status : Status ) : module;

(* ---------------------------------------------------------------------------

 * function:  module.enqueue( queue, value, status )
 * ---------------------------------------------------------------------------
 *
 * Adds a new entry <value> to the head of queue <queue>  and returns <queue>.
 * The new entry  is added  by reference,  NO data is copied.  If the queue is
 * full,  then  NO  new entry is added to <queue>.  The function fails  if NIL
 * is passed in for <queue> or <value>.
 *
 * The status of the operation is passed back in <status>. *)

PROCEDURE enqueue ( queue : module; value : Value Type?; VAR status : Status );

(* ---------------------------------------------------------------------------

 * function:  module.dequeue( queue, status )
 * ---------------------------------------------------------------------------
 *
 * Removes the oldest value from the tail of queue <queue> and returns it.  If
 * the queue is empty or if NIL is passed in for <queue>,  NIL is returned.
 *
 * The status of the operation is passed back in <status>. *)

PROCEDURE dequeue ( queue : module; VAR status : Status ) : Value Type?;

(* ---------------------------------------------------------------------------

 * function:  module.capacity( queue )
 * ---------------------------------------------------------------------------
 *
 * Returns the total capacity of queue <queue>,  returns zero if NIL is passed
 * in for <queue>. *)

PROCEDURE capacity ( queue : module ) : Capacity;

(* ---------------------------------------------------------------------------

 * function:  module.entryCount( stack )
 * ---------------------------------------------------------------------------
 *
 * Returns  the  number of entries  stored in stack <stack>,  returns  zero if
 * NIL is passed in for <stack>. *)

PROCEDURE entryCount ( VAR stack : module ) : Capacity;

(* ---------------------------------------------------------------------------

 * function:  module.isResizable( queue )
 * ---------------------------------------------------------------------------
 *
 * Returns TRUE  if the  capacity of <queue> can change after <queue> has been
 * instatiated,  returns FALSE otherwise. *)

PROCEDURE isResizable ( queue : module ) : BOOLEAN;

(* ---------------------------------------------------------------------------

 * function:  module.dispose ( queue )
 * ---------------------------------------------------------------------------
 *
 * Disposes of queue object <queue> and returns NIL. *)

PROCEDURE dispose ( VAR queue : module ) : module;

END module.@]