c954a01.a

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-- C954A01.A
--
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--
--     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.
--*
--
-- OBJECTIVE:
--      Check that if a task requeued without abort on a protected entry queue
--      is aborted, the abort is deferred until the entry call completes,
--      after which the task becomes completed.
--
-- TEST DESCRIPTION:
--      Declare a protected type which simulates a printer device driver
--      (foundation code).
--
--      Declare a task which simulates a printer server for multiple printers.
--
--      For the protected type, declare an entry with a barrier that is set
--      false by a protected procedure (which simulates starting a print job
--      on the printer), and is set true by a second protected procedure (which
--      simulates a handler called when the printer interrupts, indicating
--      that printing is done).
--
--      For the task, declare an entry whose corresponding accept statement
--      contains a call to first protected procedure of the protected type
--      (which sets the barrier of the protected entry to false), followed by
--      a requeue with abort to the protected entry. Declare a second entry
--      which does nothing.
--
--      Declare a "requesting" task which calls the printer server task entry
--      (and thus executes the requeue). Attempt to abort the requesting
--      task. Verify that it is not aborted. Call the second protected
--      procedure of the protected type (the interrupt handler) and verify that
--      the protected entry completes for the requesting task. Verify that
--      the requesting task is then aborted.
--
-- TEST FILES:
--      This test depends on the following foundation code:
--
--         F954A00.A
--
--
-- CHANGE HISTORY:
--      06 Dec 94   SAIC    ACVC 2.0
--      10 Oct 96   SAIC    Added pragma elaborate.
--
--!

package C954A01_0 is  -- Printer server abstraction.

   -- Simulate a system with multiple printers. The entry Print requests
   -- that data be printed on the next available printer. The entry call
   -- is accepted when a printer is available, and completes when printing
   -- is done.


   task Printer_Server is
      entry Print (File_Name : String);        -- Test the requeue statement.
      entry Verify_Results;                    -- Artifice for test purposes.
   end Printer_Server;

end C954A01_0;


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


with Report;
with ImpDef;

with F954A00;              -- Printer device abstraction.
use  F954A00;
pragma Elaborate(F954A00);

package body C954A01_0 is  -- Printer server abstraction.

   task body Printer_Server is
      Printers_Busy  : Boolean    := True;
      Index          : Printer_ID := 1;
      Print_Accepted : Boolean    := False;
   begin

      loop
         -- Wait for a printer to become available:

         while Printers_Busy loop
            Printers_Busy := False;                        -- Exit loop if
                                                           -- entry accepted.
            select
               Printer(Index).Done_Printing;               -- Accepted immed.
                                                           -- when printer is
                                                           -- available.
            else
               Index := 1 + (Index mod Number_Of_Printers);-- Entry not immed.
               Printers_Busy := True;                      -- accepted; keep
            end select;                                    -- looping.
         end loop;
                                                           -- Value of Index
                                                           -- at loop exit
                                                           -- identifies the
                                                           -- avail. printer.

         -- Wait for a print request or terminate:

         select
            accept Print (File_Name : String) do
               Print_Accepted := True;                     -- Allow
                                                           -- Verify_Results
                                                           -- to be accepted.

               Printer(Index).Start_Printing (File_Name);  -- Begin printing on
                                                           -- the available
               --                        --                -- printer.
               -- Requeue is tested here --
               --                        --
                                                           -- Requeue caller so
               requeue Printer(Index).Done_Printing;       -- server task free
                                                           -- to accept other
            end Print;                                     -- requests.
         or
            --  Guard ensures that Verify_Results cannot be accepted
            --  until after Print has been accepted. This avoids a
            --  race condition in the main program.

            when Print_Accepted => accept Verify_Results;  -- Artifice for
                                                           -- testing purposes.
         or
            terminate;
         end select;

         -- Allow other tasks to get control
         delay ImpDef.Minimum_Task_Switch;

      end loop;

   exception
      when others =>
         Report.Failed ("Exception raised in Printer_Server task");
   end Printer_Server;


end C954A01_0;


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


with Report;
with ImpDef;

with F954A00;    -- Printer device abstraction.
with C954A01_0;  -- Printer server abstraction.

use  C954A01_0;
use  F954A00;

procedure C954A01 is

   Long_Enough : constant Duration := ImpDef.Switch_To_New_Task;

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

   task Print_Request;                       -- Send a print request.

   task body Print_Request is
      My_File : constant String := "MYFILE.DAT";
   begin
      Printer_Server.Print (My_File);          -- Invoke requeue statement.
      Report.Failed ("Task continued execution following entry call");
   exception
      when others =>
         Report.Failed ("Exception raised in Print_Request task");
   end Print_Request;

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

begin  -- Main program.

   Report.Test ("C954A01", "Requeue without abort - check that the abort " &
            "is deferred until after the rendezvous completes. (Task to PO)");

   --  To pass this test, the following must be true:
   -- 
   --     (A) The abort of Print_Request is deferred until after the
   --         Done_Printing entry body completes.
   --     (B) Print_Request aborts after the Done_Printing entry call
   --         completes.
   -- 
   --  Call the entry Verify_Results. The entry call will not be accepted
   --  until after Print_Request has been requeued to Done_Printing.

   Printer_Server.Verify_Results;           -- Accepted after Print_Request is
                                            -- requeued to Done_Printing.

   -- Simulate an application which needs access to the printer within
   -- a specified time, and which aborts the current printer job if time
   -- runs out.

   select
      Printer(1).Done_Printing;             -- Wait for printer to come free.
   or
      delay Long_Enough;                    -- Print job took too long.
      abort Print_Request;                  -- Abort print job.
   end select;

   Printer_Server.Verify_Results;           -- Abortion completion point: force
                                            -- abort to complete (if it's going
                                            -- to).

   --  Verify that the Done_Printing entry body has not yet completed,
   --  and thus that Print_Request has not been aborted.

   if Printer(1).Is_Done then
      Report.Failed ("Target entry of requeue executed prematurely");
   elsif Print_Request'Terminated then
      Report.Failed ("Caller was aborted before entry was complete");
   else

      Printer(1).Handle_Interrupt;          -- Simulate a printer interrupt,
                                            -- signaling that printing is
                                            -- done.

      --  The Done_Printing entry body will complete before the next protected
      --  action is called (Printer(1).Is_Done). Verify (A) and (B): that the
      --  Print_Request is aborted.

      Printer_Server.Verify_Results;        -- Abortion completion point: force
                                            -- Print_Request abort to complete.

      if not Printer(1).Is_Done then
         Report.Failed ("Target entry of requeue did not complete");
      end if;

      if not Print_Request'Terminated then
         Report.Failed ("Task not aborted following completion of entry call");
         abort Print_Request;               -- Try to kill hung task.
      end if;

   end if;

   Report.Result;

end C954A01;