Subversion Repositories openrisc_2011-10-31

------------------------------------------------------------------------------
--                                                                          --
--                         GNAT LIBRARY COMPONENTS                          --
--                                                                          --
--                      G N A T . S E M A P H O R E S                       --
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--                                 S p e c                                  --
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--                     Copyright (C) 2003-2005, AdaCore                     --
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------------------------------------------------------------------------------
 
--  This package provides classic counting semaphores and binary semaphores.
--  Both types are visibly defined as protected types so that users can make
--  conditional and timed calls when appropriate.
 
with System;
 
package GNAT.Semaphores is
 
   Default_Ceiling : constant System.Priority := System.Default_Priority;
   --  A convenient value for the priority discriminants that follow
 
   ------------------------
   -- Counting_Semaphore --
   ------------------------
 
   protected type Counting_Semaphore
      (Initial_Value : Natural;
      --  A counting semaphore contains an internal counter.  The initial
      --  value of this counter is set by clients via the discriminant.
 
      Ceiling : System.Priority)
      --  Users must specify the ceiling priority for the object. If the
      --  Real-Time Systems Annex is not in use this value is not important.
   is
      pragma Priority (Ceiling);
 
      entry Seize;
      --  Blocks caller until/unless the semaphore's internal counter is
      --  greater than zero. Decrements the semaphore's internal counter when
      --  executed.
 
      procedure Release;
      --  Increments the semaphore's internal counter
 
   private
      Count : Natural := Initial_Value;
   end Counting_Semaphore;
 
   ----------------------
   -- Binary_Semaphore --
   ----------------------
 
   protected type Binary_Semaphore
     (Initially_Available : Boolean;
      --  Binary semaphores are either available or not; there is no internal
      --  count involved. The discriminant value determines whether the
      --  individual object is initially available.
 
      Ceiling : System.Priority)
      --  Users must specify the ceiling priority for the object. If the
      --  Real-Time Systems Annex is not in use this value is not important.
   is
      pragma Priority (Ceiling);
 
      entry Seize;
      --  Blocks the caller unless/until semaphore is available. After
      --  execution the semaphore is no longer available.
 
      procedure Release;
      --  Makes the semaphore available
 
   private
      Available : Boolean := Initially_Available;
   end Binary_Semaphore;
 
end GNAT.Semaphores;