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-- C940002.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 protected object provides coordinated access to shared
-- data. Check that it can implement a semaphore-like construct using a
-- parameterless procedure which allows a specific maximum number of tasks
-- to run and excludes all others
--
-- TEST DESCRIPTION:
-- Implement a counting semaphore type that can be initialized to a
-- specific number of available resources. Declare an entry for
-- requesting a resource and a procedure for releasing it. Declare an
-- object of this type, initialized to two resources. Declare and start
-- three tasks each of which asks for a resource. Verify that only two
-- resources are granted and that the last task in is queued.
--
--
-- CHANGE HISTORY:
-- 06 Dec 94 SAIC ACVC 2.0
--
--!
package C940002_0 is
-- Semaphores
protected type Semaphore_Type (Resources_Available : Integer :=1) is
entry Request;
procedure Release;
function Available return Integer;
private
Currently_Available : Integer := Resources_Available;
end Semaphore_Type;
Max_Resources : constant Integer := 2;
Resource : Semaphore_Type (Max_Resources);
end C940002_0;
-- Semaphores;
--========================================================--
package body C940002_0 is
-- Semaphores
protected body Semaphore_Type is
entry Request when Currently_Available >0 is -- when granted, secures
begin -- a resource
Currently_Available := Currently_Available - 1;
end Request;
procedure Release is -- when called, releases
begin -- a resource
Currently_Available := Currently_Available + 1;
end Release;
function Available return Integer is -- returns number of
begin -- available resources
return Currently_Available;
end Available;
end Semaphore_Type;
end C940002_0;
-- Semaphores;
--========================================================--
package C940002_1 is
-- Task_Pkg
task type Requesting_Task is
entry Done; -- call on Done instructs the task
end Requesting_Task; -- to release resource
type Task_Ptr is access Requesting_Task;
protected Counter is
procedure Increment;
procedure Decrement;
function Number return integer;
private
Count : Integer := 0;
end Counter;
protected Hold_Lock is
procedure Lock;
procedure Unlock;
function Locked return Boolean;
private
Lock_State : Boolean := true; -- starts out locked
end Hold_Lock;
end C940002_1;
-- Task_Pkg
--========================================================--
with Report;
with C940002_0;
-- Semaphores;
package body C940002_1 is
-- Task_Pkg is
protected body Counter is
procedure Increment is
begin
Count := Count + 1;
end Increment;
procedure Decrement is
begin
Count := Count - 1;
end Decrement;
function Number return Integer is
begin
return Count;
end Number;
end Counter;
protected body Hold_Lock is
procedure Lock is
begin
Lock_State := true;
end Lock;
procedure Unlock is
begin
Lock_State := false;
end Unlock;
function Locked return Boolean is
begin
return Lock_State;
end Locked;
end Hold_Lock;
task body Requesting_Task is
begin
C940002_0.Resource.Request; -- request a resource
-- if resource is not available,
-- task will be queued to wait
Counter.Increment; -- add to count of resources obtained
Hold_Lock.Unlock; -- and unlock Lock - system is stable;
-- status may now be queried
accept Done do -- hold resource until Done is called
C940002_0.Resource.Release; -- release the resource and
Counter.Decrement; -- note release
end Done;
exception
when others => Report.Failed ("Unexpected Exception in Requesting_Task");
end Requesting_Task;
end C940002_1;
-- Task_Pkg;
--========================================================--
with Report;
with ImpDef;
with C940002_0,
-- Semaphores,
C940002_1;
-- Task_Pkg;
procedure C940002 is
package Semaphores renames C940002_0;
package Task_Pkg renames C940002_1;
Ptr1,
Ptr2,
Ptr3 : Task_Pkg.Task_Ptr;
Num : Integer;
procedure Spinlock is
begin
-- loop until unlocked
while Task_Pkg.Hold_Lock.Locked loop
delay ImpDef.Minimum_Task_Switch;
end loop;
Task_Pkg.Hold_Lock.Lock;
end Spinlock;
begin
Report.Test ("C940002", "Check that a protected record can be used to " &
"control access to resources");
if (Task_Pkg.Counter.Number /=0)
or (Semaphores.Resource.Available /= 2) then
Report.Failed ("Wrong initial conditions");
end if;
Ptr1 := new Task_Pkg.Requesting_Task; -- newly allocated task requests
-- resource; request for resource should
-- be granted
Spinlock; -- ensure that task obtains resource
-- Task 1 waiting for call to Done
-- One resource assigned to task 1
-- One resource still available
if (Task_Pkg.Counter.Number /= 1)
or (Semaphores.Resource.Available /= 1) then
Report.Failed ("Resource not assigned to task 1");
end if;
Ptr2 := new Task_Pkg.Requesting_Task; -- newly allocated task requests
-- resource; request for resource should
-- be granted
Spinlock; -- ensure that task obtains resource
-- Task 1 waiting for call to Done
-- Task 2 waiting for call to Done
-- Resources held by tasks 1 and 2
-- No resources available
if (Task_Pkg.Counter.Number /= 2)
or (Semaphores.Resource.Available /= 0) then
Report.Failed ("Resource not assigned to task 2");
end if;
Ptr3 := new Task_Pkg.Requesting_Task; -- newly allocated task requests
-- resource; request for resource should
-- be denied and task queued to wait for
-- next available resource
Ptr1.all.Done; -- Task 1 releases resource and lock
-- Resource should be given to queued task
Spinlock; -- ensure that resource is released
-- Task 1 holds no resource
-- One resource still assigned to task 2
-- One resource assigned to task 3
-- No resources available
if (Task_Pkg.Counter.Number /= 2)
or (Semaphores.Resource.Available /= 0) then
Report.Failed ("Resource not properly released/assigned to task 3");
end if;
Ptr2.all.Done; -- Task 2 releases resource and lock
-- No outstanding request for resource
-- Tasks 1 and 2 hold no resources
-- One resource assigned to task 3
-- One resource available
if (Task_Pkg.Counter.Number /= 1)
or (Semaphores.Resource.Available /= 1) then
Report.Failed ("Resource not properly released from task 2");
end if;
Ptr3.all.Done; -- Task 3 releases resource and lock
-- All resources released
-- All tasks terminated (or close)
-- Two resources available
if (Task_Pkg.Counter.Number /=0)
or (Semaphores.Resource.Available /= 2) then
Report.Failed ("Resource not properly released from task 3");
end if;
Report.Result;
end C940002;
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