Subversion Repositories openrisc

-- FC70B00.A

--

--                             Grant of Unlimited Rights

--

--     Under contracts F33600-87-D-0337, F33600-84-D-0280, MDA903-79-C-0687,

--     F08630-91-C-0015, and DCA100-97-D-0025, the U.S. Government obtained

--     unlimited rights in the software and documentation contained herein.

--     Unlimited rights are defined in DFAR 252.227-7013(a)(19).  By making

--     this public release, the Government intends to confer upon all

--     recipients unlimited rights  equal to those held by the Government.

--     These rights include rights to use, duplicate, release or disclose the

--     released technical data and computer software in whole or in part, in

--     any manner and for any purpose whatsoever, and to have or permit others

--     to do so.

--

--                                    DISCLAIMER

--

--     ALL MATERIALS OR INFORMATION HEREIN RELEASED, MADE AVAILABLE OR

--     DISCLOSED ARE AS IS.  THE GOVERNMENT MAKES NO EXPRESS OR IMPLIED

--     WARRANTY AS TO ANY MATTER WHATSOEVER, INCLUDING THE CONDITIONS OF THE

--     SOFTWARE, DOCUMENTATION OR OTHER INFORMATION RELEASED, MADE AVAILABLE

--     OR DISCLOSED, OR THE OWNERSHIP, MERCHANTABILITY, OR FITNESS FOR A

--     PARTICULAR PURPOSE OF SAID MATERIAL.

--*

--

-- FOUNDATION DESCRIPTION:

--      This foundation defines a generic list abstraction. List elements can

--      be of any (nonlimited) type. Lists are implemented as singly linked

--      lists. Access to list elements is sequential. For each list, pointers

--      are maintained to the first and last elements in the list, as well as

--      the next element to be accessed.

--

-- CHANGE HISTORY:

--      06 Dec 94   SAIC    ACVC 2.0

--

--!

generic                           -- List abstraction.

   type Element_Type is private;  -- List elems can be of any nonlimited type.

package FC70B00 is

   type List_Type is limited private;

   -- Return true if current element is last in the list.

   function End_Of_List (L : List_Type) return Boolean;

   -- Read current element value; do NOT advance "current" pointer.

   procedure View_Element (L : in List_Type; E : out Element_Type);

   -- Read from current element and advance "current" pointer.

   procedure Read_Element (L : in out List_Type; E : out Element_Type);

   -- Write to current element and advance "current" pointer.

   procedure Write_Element (L : in out List_Type; E : in Element_Type);

   -- Add element to end of list.

   procedure Add_Element (L : in out List_Type; E : in Element_Type);

   -- Set "current" pointer to first list element.

   procedure Reset (L : in out List_Type);

private

   type Node_Type;

   type Node_Pointer is access Node_Type;

   type Node_Type is record

      Item : Element_Type;

      Next : Node_Pointer;

   end record;

   type List_Type is record

      First   : Node_Pointer;

      Current : Node_Pointer;

      Last    : Node_Pointer;

   end record;

end FC70B00;

     --==================================================================--

package body FC70B00 is

   function End_Of_List (L : List_Type) return Boolean is

   begin

      return (L.Current = null);

   end End_Of_List;

   procedure View_Element (L : in List_Type; E : out Element_Type) is

   begin

      -- ... Error-checking code omitted for brevity.

      E := L.Current.Item;               -- Retrieve current element.

   end View_Element;

   procedure Read_Element (L : in out List_Type; E : out Element_Type) is

   begin

      -- ... Error-checking code omitted for brevity.

      E         := L.Current.Item;       -- Retrieve current element.

      L.Current := L.Current.Next;       -- Advance "current" pointer.

   end Read_Element;

   procedure Write_Element (L : in out List_Type; E : in Element_Type) is

   begin

      -- ... Error-checking code omitted for brevity.

      L.Current.Item := E;               -- Write to current element.

      L.Current      := L.Current.Next;  -- Advance "current" pointer.

   end Write_Element;

   procedure Add_Element (L : in out List_Type; E : in Element_Type) is

      New_Node : Node_Pointer := new Node_Type'(E, null);

   begin

      if L.First = null then             -- No elements in list, so add new

         L.First := New_Node;            -- element at beginning of list.

      else

         L.Last.Next := New_Node;        -- Add new element at end of list.

      end if;

      L.Last := New_Node;                -- Set last-in-list pointer.

   end Add_Element;

   procedure Reset (L : in out List_Type) is

   begin

      L.Current := L.First;              -- Set "current" pointer to first

   end Reset;                            -- list element.

end FC70B00;