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 Ada Core Technologies, Inc.              --
  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 2,  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.  See the GNU General Public License --
  17 -- for  more details.  You should have  received  a copy of the GNU General --
  18 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
  19 -- to  the Free Software Foundation,  59 Temple Place - Suite 330,  Boston, --
  20 -- MA 02111-1307, USA.                                                      --
  21 --                                                                          --
  22 -- As a special exception,  if other files  instantiate  generics from this --
  23 -- unit, or you link  this unit with other files  to produce an executable, --
  24 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  25 -- covered  by the  GNU  General  Public  License.  This exception does not --
  26 -- however invalidate  any other reasons why  the executable file  might be --
  27 -- covered by the  GNU Public License.                                      --
  28 --                                                                          --
  29 -- GNAT was originally developed  by the GNAT team at  New York University. --
  30 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 --  This package provides a thread-safe asynchronous communication facility
  35 --  in the form of mailboxes. Individual mailbox objects are bounded in size
  36 --  to a value specified by their Capacity discriminants.
  37
  38 --  Mailboxes actually hold references to messages, not the message values
  39 --  themselves.
  40
  41 --  Type Mailbox is defined explicitly as a protected type (via derivation
  42 --  from a protected type) so that clients may treat them accordingly (for
  43 --  example, by making conditional/timed entry calls).
  44
  45 with System;
  46 with GNAT.Bounded_Buffers;
  47
  48 generic
  49    type Message (<>) is limited private;
  50    type Message_Reference is access all Message;
  51    --  Mailboxes hold references to Message values, of this type
  52
  53 package GNAT.Bounded_Mailboxes is
  54    pragma Preelaborate;
  55
  56    package Message_Refs is
  57       new GNAT.Bounded_Buffers (Message_Reference);
  58
  59    type Mailbox is new Message_Refs.Bounded_Buffer;
  60
  61    --  Type Mailbox has two inherited discriminants:
  62
  63    --  Capacity : Positive;
  64    --     Capacity is the maximum number of Message references
  65    --     possibly contained at any given instant.
  66
  67    --  Ceiling : System.Priority;
  68    --     Users must specify the ceiling priority for the object.
  69    --     If the Real-Time Systems Annex is not in use this value
  70    --     is not important.
  71
  72    --  Protected type Mailbox has the following inherited interface:
  73
  74    --  entry Insert (Item : in Message_Reference);
  75    --     Insert Item into the Mailbox. Blocks caller
  76    --     until space is available.
  77
  78    --  entry Remove (Item : out Message_Reference);
  79    --     Remove next available Message_Reference from Mailbox.
  80    --     Blocks caller until a Message_Reference is available.
  81
  82    --  function Empty return Boolean;
  83    --     Returns whether the Mailbox contains any Message_References.
  84    --     Note: State may change immediately after call returns.
  85
  86    --  function Full return Boolean;
  87    --     Returns whether any space remains within the Mailbox.
  88    --     Note: State may change immediately after call returns.
  89
  90    --  function Extent return Natural;
  91    --     Returns the number of Message_Reference values currently held
  92    --     within the Mailbox.
  93    --     Note: State may change immediately after call returns.
  94
  95    Default_Ceiling : constant System.Priority := Message_Refs.Default_Ceiling;
  96    --  A convenience value for the Ceiling discriminant
  97
  98 end GNAT.Bounded_Mailboxes;