blob: 027b78aac65d3ec0ad6e10db3615b6ff80511349 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
------------------------------------------------------------------------------
-- --
-- GNAT LIBRARY COMPONENTS --
-- --
-- G N A T . S E M A P H O R E S --
-- --
-- S p e c --
-- --
-- Copyright (C) 2003-2010, AdaCore --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 3, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. --
-- --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception, --
-- version 3.1, as published by the Free Software Foundation. --
-- --
-- You should have received a copy of the GNU General Public License and --
-- a copy of the GCC Runtime Library Exception along with this program; --
-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
-- <http://www.gnu.org/licenses/>. --
-- --
-- GNAT was originally developed by the GNAT team at New York University. --
-- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
-- --
------------------------------------------------------------------------------
-- This package provides classic counting semaphores and binary semaphores.
-- Both types are visibly defined as protected types so that users can make
-- conditional and timed calls when appropriate.
with System;
package GNAT.Semaphores is
Default_Ceiling : constant System.Priority := System.Default_Priority;
-- A convenient value for the priority discriminants that follow
------------------------
-- Counting_Semaphore --
------------------------
protected type Counting_Semaphore
(Initial_Value : Natural;
-- A counting semaphore contains an internal counter. The initial
-- value of this counter is set by clients via the discriminant.
Ceiling : System.Priority)
-- Users must specify the ceiling priority for the object. If the
-- Real-Time Systems Annex is not in use this value is not important.
is
pragma Priority (Ceiling);
entry Seize;
-- Blocks caller until/unless the semaphore's internal counter is
-- greater than zero. Decrements the semaphore's internal counter when
-- executed.
procedure Release;
-- Increments the semaphore's internal counter
private
Count : Natural := Initial_Value;
end Counting_Semaphore;
----------------------
-- Binary_Semaphore --
----------------------
protected type Binary_Semaphore
(Initially_Available : Boolean;
-- Binary semaphores are either available or not; there is no internal
-- count involved. The discriminant value determines whether the
-- individual object is initially available.
Ceiling : System.Priority)
-- Users must specify the ceiling priority for the object. If the
-- Real-Time Systems Annex is not in use this value is not important.
is
pragma Priority (Ceiling);
entry Seize;
-- Blocks the caller unless/until semaphore is available. After
-- execution the semaphore is no longer available.
procedure Release;
-- Makes the semaphore available
private
Available : Boolean := Initially_Available;
end Binary_Semaphore;
end GNAT.Semaphores;
|
