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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 _ B U F F E R S --
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6 -- --
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7 -- S p e c --
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8 -- --
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131
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9 -- Copyright (C) 2003-2018, AdaCore --
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111
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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 generic bounded buffer abstraction.
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33 -- Instances are useful directly or as parts of the implementations of other
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34 -- abstractions, such as mailboxes.
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35
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36 -- Bounded_Buffer is declared explicitly as a protected type, rather than as
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37 -- a simple limited private type completed as a protected type, so that
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38 -- clients may make calls accordingly (i.e., conditional/timed entry calls).
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39
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40 with System;
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41
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42 generic
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43 type Element is private;
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44 -- The type of the values contained within buffer objects
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45
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46 package GNAT.Bounded_Buffers is
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47 pragma Pure;
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48
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49 type Content is array (Positive range <>) of Element;
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50 -- Content is an internal artefact that cannot be hidden because protected
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51 -- types cannot contain type declarations.
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52
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53 Default_Ceiling : constant System.Priority := System.Default_Priority;
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54 -- A convenience value for the Ceiling discriminant
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55
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56 protected type Bounded_Buffer
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57 (Capacity : Positive;
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58 -- Objects of type Bounded_Buffer specify the maximum number of Element
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59 -- values they can hold via the discriminant Capacity.
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60
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61 Ceiling : System.Priority)
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62 -- Users must specify the ceiling priority for the object. If the
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63 -- Real-Time Systems Annex is not in use this value is not important.
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64 is
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65 pragma Priority (Ceiling);
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66
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67 entry Insert (Item : Element);
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68 -- Insert Item into the buffer, blocks caller until space is available
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69
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70 entry Remove (Item : out Element);
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71 -- Remove next available Element from buffer. Blocks caller until an
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72 -- Element is available.
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73
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74 function Empty return Boolean;
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75 -- Returns whether the instance contains any Elements.
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76 -- Note: State may change immediately after call returns.
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77
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78 function Full return Boolean;
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79 -- Returns whether any space remains within the instance.
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80 -- Note: State may change immediately after call returns.
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81
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82 function Extent return Natural;
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83 -- Returns the number of Element values currently held
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84 -- within the instance.
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85 -- Note: State may change immediately after call returns.
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86
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87 private
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88 Values : Content (1 .. Capacity);
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89 -- The container for the values held by the buffer instance
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90
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91 Next_In : Positive := 1;
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92 -- The index of the next Element inserted. Wraps around
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93
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94 Next_Out : Positive := 1;
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95 -- The index of the next Element removed. Wraps around
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96
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97 Count : Natural := 0;
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98 -- The number of Elements currently held
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99 end Bounded_Buffer;
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100
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101 end GNAT.Bounded_Buffers;
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