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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 . P R O T E C T E D _ O B J E C T S -- | |
6 | -- -- | |
7 | -- S p e c -- | |
8 | -- -- | |
fbf5a39b | 9 | -- Copyright (C) 1992-2003, Free Software Foundation, Inc. -- |
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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 | -- -- | |
71ff80dc | 29 | -- GNARL was developed by the GNARL team at Florida State University. -- |
fbf5a39b | 30 | -- Extensive contributions were provided by Ada Core Technologies, Inc. -- |
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31 | -- -- |
32 | ------------------------------------------------------------------------------ | |
33 | ||
34 | -- This package provides necessary definitions to handle simple (i.e without | |
35 | -- entries) protected objects. | |
fbf5a39b | 36 | |
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37 | -- All the routines that handle protected objects with entries have been moved |
38 | -- to two children: Entries and Operations. Note that Entries only contains | |
39 | -- the type declaration and the OO primitives. This is needed to avoid | |
40 | -- circular dependency. | |
41 | ||
42 | -- This package is part of the high level tasking interface used by the | |
43 | -- compiler to expand Ada 95 tasking constructs into simpler run time calls | |
44 | -- (aka GNARLI, GNU Ada Run-time Library Interface) | |
45 | ||
46 | -- Note: the compiler generates direct calls to this interface, via Rtsfind. | |
47 | -- Any changes to this interface may require corresponding compiler changes | |
48 | -- in exp_ch9.adb and possibly exp_ch7.adb | |
49 | ||
50 | package System.Tasking.Protected_Objects is | |
51 | pragma Elaborate_Body; | |
52 | ||
53 | --------------------------------- | |
54 | -- Compiler Interface (GNARLI) -- | |
55 | --------------------------------- | |
56 | ||
57 | -- The compiler will expand in the GNAT tree the following construct: | |
fbf5a39b | 58 | |
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59 | -- protected PO is |
60 | -- procedure P; | |
61 | -- private | |
62 | -- open : boolean := false; | |
63 | -- end PO; | |
fbf5a39b | 64 | |
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65 | -- protected body PO is |
66 | -- procedure P is | |
67 | -- ...variable declarations... | |
68 | -- begin | |
69 | -- ...B... | |
70 | -- end P; | |
71 | -- end PO; | |
fbf5a39b | 72 | |
cacbc350 | 73 | -- as follows: |
fbf5a39b | 74 | |
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75 | -- protected type poT is |
76 | -- procedure p; | |
77 | -- private | |
78 | -- open : boolean := false; | |
79 | -- end poT; | |
80 | -- type poTV is limited record | |
81 | -- open : boolean := false; | |
82 | -- _object : aliased protection; | |
83 | -- end record; | |
84 | -- procedure poPT__pN (_object : in out poTV); | |
85 | -- procedure poPT__pP (_object : in out poTV); | |
86 | -- freeze poTV [ | |
fbf5a39b | 87 | -- procedure poTVI (_init : in out poTV) is |
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88 | -- begin |
89 | -- _init.open := false; | |
fbf5a39b | 90 | -- object-init-proc (_init._object); |
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91 | -- initialize_protection (_init._object'unchecked_access, |
92 | -- unspecified_priority); | |
93 | -- return; | |
94 | -- end _init_proc; | |
95 | -- ] | |
96 | -- po : poT; | |
fbf5a39b AC |
97 | -- poTVI (poTV!(po)); |
98 | ||
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99 | -- procedure poPT__pN (_object : in out poTV) is |
100 | -- poR : protection renames _object._object; | |
101 | -- openP : boolean renames _object.open; | |
102 | -- ...variable declarations... | |
103 | -- begin | |
104 | -- ...B... | |
105 | -- return; | |
106 | -- end poPT__pN; | |
fbf5a39b | 107 | |
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108 | -- procedure poPT__pP (_object : in out poTV) is |
109 | -- procedure _clean is | |
110 | -- begin | |
111 | -- unlock (_object._object'unchecked_access); | |
112 | -- return; | |
113 | -- end _clean; | |
114 | -- begin | |
115 | -- lock (_object._object'unchecked_access); | |
116 | -- B2b : begin | |
117 | -- poPT__pN (_object); | |
118 | -- at end | |
119 | -- _clean; | |
120 | -- end B2b; | |
121 | -- return; | |
122 | -- end poPT__pP; | |
123 | ||
124 | Null_Protected_Entry : constant := Null_Entry; | |
125 | ||
126 | Max_Protected_Entry : constant := Max_Entry; | |
127 | ||
128 | type Protected_Entry_Index is new Entry_Index | |
129 | range Null_Protected_Entry .. Max_Protected_Entry; | |
130 | ||
131 | type Barrier_Function_Pointer is access | |
132 | function | |
133 | (O : System.Address; | |
134 | E : Protected_Entry_Index) | |
135 | return Boolean; | |
136 | -- Pointer to a function which evaluates the barrier of a protected | |
137 | -- entry body. O is a pointer to the compiler-generated record | |
138 | -- representing the protected object, and E is the index of the | |
139 | -- entry serviced by the body. | |
140 | ||
141 | type Entry_Action_Pointer is access | |
142 | procedure | |
143 | (O : System.Address; | |
144 | P : System.Address; | |
145 | E : Protected_Entry_Index); | |
146 | -- Pointer to a procedure which executes the sequence of statements | |
147 | -- of a protected entry body. O is a pointer to the compiler-generated | |
148 | -- record representing the protected object, P is a pointer to the | |
149 | -- record of entry parameters, and E is the index of the | |
150 | -- entry serviced by the body. | |
151 | ||
152 | type Entry_Body is record | |
153 | Barrier : Barrier_Function_Pointer; | |
154 | Action : Entry_Action_Pointer; | |
155 | end record; | |
156 | -- The compiler-generated code passes objects of this type to the GNARL | |
157 | -- to allow it to access the executable code of an entry body. | |
158 | ||
159 | type Entry_Body_Access is access all Entry_Body; | |
160 | ||
161 | type Protection is limited private; | |
162 | -- This type contains the GNARL state of a protected object. The | |
163 | -- application-defined portion of the state (i.e. private objects) | |
164 | -- is maintained by the compiler-generated code. | |
165 | -- Note that there are now 2 Protection types. One for the simple | |
166 | -- case (no entries) and one for the general case that needs the whole | |
167 | -- Finalization mechanism. | |
168 | -- This split helps in the case of restricted run time where we want to | |
169 | -- minimize the size of the code. | |
170 | ||
171 | type Protection_Access is access all Protection; | |
172 | ||
173 | Null_PO : constant Protection_Access := null; | |
174 | ||
175 | procedure Initialize_Protection | |
176 | (Object : Protection_Access; | |
177 | Ceiling_Priority : Integer); | |
178 | -- Initialize the Object parameter so that it can be used by the runtime | |
179 | -- to keep track of the runtime state of a protected object. | |
180 | ||
181 | procedure Lock (Object : Protection_Access); | |
182 | -- Lock a protected object for write access. Upon return, the caller | |
183 | -- owns the lock to this object, and no other call to Lock or | |
184 | -- Lock_Read_Only with the same argument will return until the | |
185 | -- corresponding call to Unlock has been made by the caller. | |
186 | ||
187 | procedure Lock_Read_Only (Object : Protection_Access); | |
188 | -- Lock a protected object for read access. Upon return, the caller | |
189 | -- owns the lock for read access, and no other calls to Lock with the | |
190 | -- same argument will return until the corresponding call to Unlock | |
191 | -- has been made by the caller. Other calls to Lock_Read_Only may (but | |
192 | -- need not) return before the call to Unlock, and the corresponding | |
193 | -- callers will also own the lock for read access. | |
194 | -- | |
195 | -- Note: we are not currently using this interface, it is provided | |
196 | -- for possible future use. At the current time, everyone uses Lock | |
197 | -- for both read and write locks. | |
198 | ||
199 | procedure Unlock (Object : Protection_Access); | |
200 | -- Relinquish ownership of the lock for the object represented by | |
201 | -- the Object parameter. If this ownership was for write access, or | |
202 | -- if it was for read access where there are no other read access | |
203 | -- locks outstanding, one (or more, in the case of Lock_Read_Only) | |
204 | -- of the tasks waiting on this lock (if any) will be given the | |
205 | -- lock and allowed to return from the Lock or Lock_Read_Only call. | |
206 | ||
207 | private | |
208 | type Protection is record | |
209 | L : aliased Task_Primitives.Lock; | |
210 | Ceiling : System.Any_Priority; | |
211 | end record; | |
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212 | |
213 | procedure Finalize_Protection (Object : in out Protection); | |
214 | -- Clean up a Protection object; in particular, finalize the associated | |
215 | -- Lock object. The compiler generates automatically calls to this | |
216 | -- procedure | |
217 | ||
218 | end System.Tasking.Protected_Objects; |