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Diffstat (limited to 'gcc/ada/g-semaph.ads')
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diff --git a/gcc/ada/g-semaph.ads b/gcc/ada/g-semaph.ads new file mode 100644 index 00000000000..a8720b32437 --- /dev/null +++ b/gcc/ada/g-semaph.ads @@ -0,0 +1,100 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT LIBRARY COMPONENTS -- +-- -- +-- G N A T . S E M A P H O R E S -- +-- -- +-- S p e c -- +-- -- +-- Copyright (C) 2003 Ada Core Technologies, Inc. -- +-- -- +-- GNAT is free software; you can redistribute it and/or modify it under -- +-- terms of the GNU General Public License as published by the Free Soft- -- +-- ware Foundation; either version 2, or (at your option) any later ver- -- +-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- +-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- +-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License -- +-- for more details. You should have received a copy of the GNU General -- +-- Public License distributed with GNAT; see file COPYING. If not, write -- +-- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, -- +-- MA 02111-1307, USA. -- +-- -- +-- As a special exception, if other files instantiate generics from this -- +-- unit, or you link this unit with other files to produce an executable, -- +-- this unit does not by itself cause the resulting executable to be -- +-- covered by the GNU General Public License. This exception does not -- +-- however invalidate any other reasons why the executable file might be -- +-- covered by the GNU Public License. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). -- +-- -- +------------------------------------------------------------------------------ + +-- 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; |