c954a03.a

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-- C954A03.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.
--*
--
-- OBJECTIVE:
--      Check that a requeue statement in an accept_statement with
--      parameters may requeue the entry call to a protected entry with no
--      parameters. Check that, if the call is queued on the new entry's
--      queue, the original caller remains blocked after the requeue, but
--      the accept_statement containing the requeue is completed.
--
--      Note that this test uses a requeue "with abort," although it does not
--      check that such a requeued caller can be aborted; that feature is
--      tested elsewhere.
--
-- 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). Verify that, following the requeue,
--      the requesting task remains blocked. Call the second entry of the
--      printer server task (the acceptance of this entry call verifies that
--      the requeue statement completed the entry call by the requesting task.
--      Call the second protected procedure of the protected type (the
--      interrupt handler) and verify that the protected entry completes for
--      the requesting task (which verifies that the requeue statement queued
--      the first task object to the protected entry).
--
-- 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 C954A03_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 C954A03_0;


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


with Report;
with ImpDef;

with F954A00;              -- Printer device abstraction.
use  F954A00;
pragma Elaborate(F954a00);

package body C954A03_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.

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

         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
                 with abort;                               -- 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;

      end loop;

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


end C954A03_0;


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


with Report;
with ImpDef;

with F954A00;    -- Printer device abstraction.
with C954A03_0;  -- Printer server abstraction.

use  C954A03_0;
use  F954A00;

procedure C954A03 is

   Long_Enough : constant Duration := ImpDef.Clear_Ready_Queue;


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

   Task_Completed : Boolean := False;          -- Testing flag.

   protected Interlock is                      -- Artifice for test purposes.
      entry Wait;                              -- Wait for lock to be released.
      procedure Release;                       -- Release the lock.
   private
      Locked : Boolean := True;
   end Interlock;


   protected body Interlock is

      entry Wait when not Locked is            -- Calls are queued until after
      --                                       -- Release is called.
      begin
         Task_Completed := True;               
      end Wait;

      procedure Release is                     -- Called by Print_Request.
      begin
         Locked := False;
      end Release;

   end Interlock;

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

   task Print_Request is                       -- Send a print request.
   end Print_Request;

   task body Print_Request is
      My_File : constant String := "MYFILE.DAT";
   begin
      Printer_Server.Print (My_File);          -- Invoke requeue statement.
      Interlock.Release;                       -- Allow main to continue.
   exception
      when others =>
         Report.Failed ("Exception raised in Print_Request task");
   end Print_Request;

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

begin  -- Main program.

   Report.Test ("C954A03", "Requeue from an Accept with parameters" &
                              " to a Protected Entry without parameters");

   -- To pass this test, the following must be true:
   --
   --    (A) The Print entry call made by the task Print_Request must be
   --        completed by the requeue statement.
   --    (B) Print_Request must remain blocked following the requeue.
   --    (C) Print_Request must be queued on the Done_Printing queue of
   --        Printer(1).
   --    (D) Print_Request must continue execution after Done_Printing is
   --        complete.
   --
   -- First, verify (A): that the Print entry call is complete.
   --
   -- Call the entry Verify_Results. If the requeue statement completed the
   -- entry call to Print, the entry call to Verify_Results should be
   -- accepted. Since the main will hang if this is NOT the case, make this
   -- a timed entry call.

   select
      Printer_Server.Verify_Results;        -- Accepted if requeue completed
                                            -- entry call to Print.
   or
      delay Long_Enough;                    -- Time out otherwise.
      Report.Failed ("Requeue did not complete entry call");
   end select;

   -- Now verify (B): that Print_Request remains blocked following the
   -- requeue. Also verify that Done_Printing (the entry to which
   -- Print_Request should have been queued) has not yet executed.

   if Printer(1).Is_Done then
      Report.Failed ("Target entry of requeue executed prematurely");
   elsif Print_Request'Terminated then
      Report.Failed ("Caller did not remain blocked after the requeue");
   else

      -- Verify (C): that Print_Request is queued on the
      -- Done_Printing queue of Printer(1).
      --
      -- Set the barrier for Printer(1).Done_Printing to true. Check
      -- that the Done flag is updated and that Print_Request terminates.

      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).

      if not Printer(1).Is_Done then
         Report.Failed ("Caller was not requeued on target entry");
      end if;

      -- Finally, verify (D): that Print_Request continues after Done_Printing
      -- completes.
      --
      -- After Done_Printing completes, there is a potential race condition
      -- between the main program and Print_Request. The protected object
      -- Interlock is provided to ensure that the check of whether
      -- Print_Request continued is made *after* it has had a chance to do so.
      -- The main program waits until the statement in Print_Request following
      -- the requeue-causing statement has executed, then checks to see
      -- whether Print_Request did in fact continue executing.
      --
      -- Note that the test will hang here if Print_Request does not continue
      -- executing following the completion of the requeued entry call.

      Interlock.Wait;                          -- Wait until Print_Request is
                                               -- done.
      if not Task_Completed then
         Report.Failed ("Caller remained blocked after target " &
                        "entry released");
      end if;

      -- Wait for Print_Request to finish before calling Report.Result.
      while not Print_Request'Terminated loop
         delay ImpDef.Minimum_Task_Switch;   
      end loop;                             

   end if;

   Report.Result;

end C954A03;