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1 | ------------------------------------------------------------------------------ |
| 2 | -- -- | |
| 3 | -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS -- | |
| 4 | -- -- | |
| 5 | -- S Y S T E M . T A S K I N G . A S Y N C _ D E L A Y S -- | |
| 6 | -- -- | |
| 7 | -- S p e c -- | |
| 8 | -- -- | |
| 07fc65c4 | 9 | -- Copyright (C) 1998-2001 Free Software Foundation, Inc. -- |
| cacbc350 RK |
10 | -- -- |
| 11 | -- GNARL 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. GNARL 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 GNARL; 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 | -- -- | |
| fbf5a39b AC |
29 | -- GNARL was developed by the GNARL team at Florida State University. -- |
| 30 | -- Extensive contributions were provided by Ada Core Technologies, Inc. -- | |
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31 | -- -- |
| 32 | ------------------------------------------------------------------------------ | |
| 33 | ||
| 07fc65c4 GB |
34 | -- This package contains the procedures to implements timeouts (delays) |
| 35 | -- for asynchronous select statements. | |
| cacbc350 RK |
36 | |
| 37 | -- Note: the compiler generates direct calls to this interface, via Rtsfind. | |
| 38 | -- Any changes to this interface may require corresponding compiler changes. | |
| 39 | ||
| 40 | package System.Tasking.Async_Delays is | |
| 41 | ||
| 42 | -- Suppose the following source code is given: | |
| 43 | ||
| 44 | -- select delay When; | |
| 45 | -- ...continuation for timeout case... | |
| 46 | -- then abort | |
| 47 | -- ...abortable part... | |
| 48 | -- end select; | |
| 49 | ||
| 50 | -- The compiler should expand this to the following: | |
| 51 | ||
| 52 | -- declare | |
| 53 | -- DB : aliased Delay_Block; | |
| 54 | -- begin | |
| 55 | -- if System.Tasking.Async_Delays.Enqueue_Duration | |
| 56 | -- (When, DB'Unchecked_Access) | |
| 57 | -- then | |
| 58 | -- begin | |
| 59 | -- A101b : declare | |
| 60 | -- procedure _clean is | |
| 61 | -- begin | |
| 62 | -- System.Tasking.Async_Delays.Cancel_Async_Delay | |
| 63 | -- (DB'Unchecked_Access); | |
| 64 | -- return; | |
| 65 | -- end _clean; | |
| 66 | -- begin | |
| 67 | -- abort_undefer.all; | |
| 68 | -- ...abortable part... | |
| 69 | -- exception | |
| 70 | -- when all others => | |
| 71 | -- declare | |
| 72 | -- E105b : exception_occurrence; | |
| 73 | -- begin | |
| 74 | -- save_occurrence (E105b, get_current_excep.all.all); | |
| 75 | -- _clean; | |
| 76 | -- reraise_occurrence_no_defer (E105b); | |
| 77 | -- end; | |
| 78 | -- at end | |
| 79 | -- _clean; | |
| 80 | -- end A101b; | |
| 81 | -- exception | |
| 82 | -- when _abort_signal => | |
| 83 | -- abort_undefer.all; | |
| 84 | -- end; | |
| 85 | -- end if; | |
| 86 | -- | |
| 87 | -- if Timed_Out (DB'Unchecked_Access) then | |
| 88 | -- ...continuation for timeout case... | |
| 89 | -- end if; | |
| 90 | -- end; | |
| 91 | ||
| 92 | ----------------- | |
| 93 | -- Delay_Block -- | |
| 94 | ----------------- | |
| 95 | ||
| 96 | type Delay_Block is limited private; | |
| 97 | type Delay_Block_Access is access all Delay_Block; | |
| 98 | ||
| 99 | function Enqueue_Duration | |
| 100 | (T : in Duration; | |
| 101 | D : Delay_Block_Access) return Boolean; | |
| 102 | -- Enqueue the specified relative delay. Returns True if the delay has | |
| 103 | -- been enqueued, False if it has already expired. | |
| 104 | -- If the delay has been enqueued, abortion is deferred. | |
| 105 | ||
| 106 | procedure Cancel_Async_Delay (D : Delay_Block_Access); | |
| 107 | -- Cancel the specified asynchronous delay | |
| 108 | ||
| 109 | function Timed_Out (D : Delay_Block_Access) return Boolean; | |
| 110 | pragma Inline (Timed_Out); | |
| 111 | -- Return True if the delay specified in D has timed out | |
| 112 | ||
| 113 | -- There are child units for delays on Ada.Calendar.Time and | |
| 114 | -- Ada.Real_Time.Time, so that an application will not need to link in | |
| 115 | -- features that is not using. | |
| 116 | ||
| 117 | private | |
| 118 | ||
| 119 | type Delay_Block is record | |
| 120 | Self_Id : Task_ID; | |
| 121 | -- ID of the calling task | |
| 122 | ||
| 123 | Level : ATC_Level_Base; | |
| 124 | -- Normally Level is the ATC nesting level of the | |
| 125 | -- async. select statement to which this delay belongs, but | |
| 126 | -- after a call has been dequeued we set it to | |
| 127 | -- ATC_Level_Infinity so that the Cancel operation can | |
| 128 | -- detect repeated calls, and act idempotently. | |
| 129 | ||
| 130 | Resume_Time : Duration; | |
| 131 | -- The absolute wake up time, represented as Duration | |
| 132 | ||
| 133 | Timed_Out : Boolean := False; | |
| 134 | -- Set to true if the delay has timed out | |
| 135 | ||
| 136 | Succ, Pred : Delay_Block_Access; | |
| 137 | -- A double linked list | |
| 138 | end record; | |
| 139 | ||
| 140 | -- The above "overlaying" of Self_ID and Level to hold other | |
| 141 | -- data that has a non-overlapping lifetime is an unabashed | |
| 142 | -- hack to save memory. | |
| 143 | ||
| 144 | procedure Time_Enqueue | |
| 145 | (T : Duration; | |
| 146 | D : Delay_Block_Access); | |
| 147 | pragma Inline (Time_Enqueue); | |
| 148 | -- Used by the child units to enqueue delays on the timer queue | |
| 149 | -- implemented in the body of this package. | |
| 150 | ||
| 151 | end System.Tasking.Async_Delays; |