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From: Magnus Therning <d94magth@und.ida.liu.se>
Subject: protected types and functions in Ada95 (Newbie)
Date: 1997/04/24
Message-ID: <335F2DF6.827@und.ida.liu.se>#1/1
X-Deja-AN: 237010927
Organization: Dept. of Computer and Information Science, Linkoping University
Newsgroups: comp.lang.ada
Date: 1997-04-24T00:00:00+00:00
List-Id: <comp.lang.ada>


I want to seize a semaphore in a function. Is that possible using the
following protected type semaphore? Functions can only take 'in'
parameters, but I need 'in out' since Seize changes the semaphore.

package Semaphore_S is

    type Kind(Num : Integer := 1) is limited private;

    procedure Seize(Sem : in out Kind);
    procedure Release(Sem : in out Kind);

private

   protected type Kind(Num : Integer := 1) is
      entry Secure;
      procedure Release; 
   private
      Count : Integer := Num;
   end Kind;

end Semaphore_S;

package body Semaphore_S is

   protected body Kind is
      Entry Secure when Count > 0 is
      begin
	 Count := Count - 1;
      end Secure;
      
      procedure Release is
      begin
	 Count := Count + 1;
      end Release;
   end Kind;

   procedure Seize(Sem : in out Kind) is
   begin  
      Sem.Secure;
   end Seize;

   procedure Release(Sem : in out Kind) is
   begin
      Sem.Release;
   end Release;

end Semaphore_S;
-- 
Magnus Therning ( d94magth@und.ida.liu.se )
http://www-und.ida.liu.se/~d94magth/