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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT LIBRARY COMPONENTS --
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4 -- --
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5 -- G N A T . B O U N D E D _ M A I L B O X E S --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 2003-2017, AdaCore --
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 -- This package provides a thread-safe asynchronous communication facility
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33 -- in the form of mailboxes. Individual mailbox objects are bounded in size
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34 -- to a value specified by their Capacity discriminants.
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35
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36 -- Mailboxes actually hold references to messages, not the message values
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37 -- themselves.
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38
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39 -- Type Mailbox is defined explicitly as a protected type (via derivation
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40 -- from a protected type) so that clients may treat them accordingly (for
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41 -- example, by making conditional/timed entry calls).
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42
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43 with System;
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44 with GNAT.Bounded_Buffers;
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45
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46 generic
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47 type Message (<>) is limited private;
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48 type Message_Reference is access all Message;
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49 -- Mailboxes hold references to Message values, of this type
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50
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51 package GNAT.Bounded_Mailboxes is
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52 pragma Preelaborate;
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53
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54 package Message_Refs is
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55 new GNAT.Bounded_Buffers (Message_Reference);
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56
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57 type Mailbox is new Message_Refs.Bounded_Buffer;
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58
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59 -- Type Mailbox has two inherited discriminants:
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60
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61 -- Capacity : Positive;
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62 -- Capacity is the maximum number of Message references
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63 -- possibly contained at any given instant.
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64
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65 -- Ceiling : System.Priority;
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66 -- Users must specify the ceiling priority for the object.
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67 -- If the Real-Time Systems Annex is not in use this value
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68 -- is not important.
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69
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70 -- Protected type Mailbox has the following inherited interface:
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71
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72 -- entry Insert (Item : Message_Reference);
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73 -- Insert Item into the Mailbox. Blocks caller
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74 -- until space is available.
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75
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76 -- entry Remove (Item : out Message_Reference);
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77 -- Remove next available Message_Reference from Mailbox.
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78 -- Blocks caller until a Message_Reference is available.
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79
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80 -- function Empty return Boolean;
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81 -- Returns whether the Mailbox contains any Message_References.
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82 -- Note: State may change immediately after call returns.
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83
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84 -- function Full return Boolean;
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85 -- Returns whether any space remains within the Mailbox.
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86 -- Note: State may change immediately after call returns.
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87
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88 -- function Extent return Natural;
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89 -- Returns the number of Message_Reference values currently held
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90 -- within the Mailbox.
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91 -- Note: State may change immediately after call returns.
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92
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93 Default_Ceiling : constant System.Priority := Message_Refs.Default_Ceiling;
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94 -- A convenience value for the Ceiling discriminant
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95
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96 end GNAT.Bounded_Mailboxes;
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