gcc/ada/g-boumai.ads

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT LIBRARY COMPONENTS                          --
   4 --                                                                          --
   5 --                 G N A T . B O U N D E D _ M A I L B O X E S              --
   6 --                                                                          --
   7 --                                 S p e c                                  --
   8 --                                                                          --
   9 --                     Copyright (C) 2003-2010, AdaCore                     --
  10 --                                                                          --
  11 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  12 -- terms of the  GNU General Public License as published  by the Free Soft- --
  13 -- ware  Foundation;  either version 3,  or (at your option) any later ver- --
  14 -- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
  15 -- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
  16 -- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 --  This package provides a thread-safe asynchronous communication facility
  33 --  in the form of mailboxes. Individual mailbox objects are bounded in size
  34 --  to a value specified by their Capacity discriminants.
  35
  36 --  Mailboxes actually hold references to messages, not the message values
  37 --  themselves.
  38
  39 --  Type Mailbox is defined explicitly as a protected type (via derivation
  40 --  from a protected type) so that clients may treat them accordingly (for
  41 --  example, by making conditional/timed entry calls).
  42
  43 with System;
  44 with GNAT.Bounded_Buffers;
  45
  46 generic
  47    type Message (<>) is limited private;
  48    type Message_Reference is access all Message;
  49    --  Mailboxes hold references to Message values, of this type
  50
  51 package GNAT.Bounded_Mailboxes is
  52    pragma Preelaborate;
  53
  54    package Message_Refs is
  55       new GNAT.Bounded_Buffers (Message_Reference);
  56
  57    type Mailbox is new Message_Refs.Bounded_Buffer;
  58
  59    --  Type Mailbox has two inherited discriminants:
  60
  61    --  Capacity : Positive;
  62    --     Capacity is the maximum number of Message references
  63    --     possibly contained at any given instant.
  64
  65    --  Ceiling : System.Priority;
  66    --     Users must specify the ceiling priority for the object.
  67    --     If the Real-Time Systems Annex is not in use this value
  68    --     is not important.
  69
  70    --  Protected type Mailbox has the following inherited interface:
  71
  72    --  entry Insert (Item : Message_Reference);
  73    --     Insert Item into the Mailbox. Blocks caller
  74    --     until space is available.
  75
  76    --  entry Remove (Item : out Message_Reference);
  77    --     Remove next available Message_Reference from Mailbox.
  78    --     Blocks caller until a Message_Reference is available.
  79
  80    --  function Empty return Boolean;
  81    --     Returns whether the Mailbox contains any Message_References.
  82    --     Note: State may change immediately after call returns.
  83
  84    --  function Full return Boolean;
  85    --     Returns whether any space remains within the Mailbox.
  86    --     Note: State may change immediately after call returns.
  87
  88    --  function Extent return Natural;
  89    --     Returns the number of Message_Reference values currently held
  90    --     within the Mailbox.
  91    --     Note: State may change immediately after call returns.
  92
  93    Default_Ceiling : constant System.Priority := Message_Refs.Default_Ceiling;
  94    --  A convenience value for the Ceiling discriminant
  95
  96 end GNAT.Bounded_Mailboxes;