]>
Commit | Line | Data |
---|---|---|
cacbc350 RK |
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. -- | |
cacbc350 RK |
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; |