1 ------------------------------------------------------------------------------
3 -- GNU ADA RUN-TIME LIBRARY (GNARL) COMPONENTS --
5 -- SYSTEM.TASKING.PROTECTED_OBJECTS.SINGLE_ENTRY --
9 -- Copyright (C) 1992-2004 Free Software Foundation, Inc. --
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. --
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. --
29 -- GNARL was developed by the GNARL team at Florida State University. --
30 -- Extensive contributions were provided by Ada Core Technologies, Inc. --
32 ------------------------------------------------------------------------------
34 -- This package provides an optimized version of Protected_Objects.Operations
35 -- and Protected_Objects.Entries making the following assumptions:
37 -- PO have only one entry
38 -- There is only one caller at a time (No_Entry_Queue)
39 -- There is no dynamic priority support (No_Dynamic_Priorities)
40 -- No Abort Statements
41 -- (No_Abort_Statements, Max_Asynchronous_Select_Nesting => 0)
42 -- PO are at library level
43 -- None of the tasks will terminate (no need for finalization)
45 -- This interface is intended to be used in the ravenscar profile, the
46 -- compiler is responsible for ensuring that the conditions mentioned above
47 -- are respected, except for the No_Entry_Queue restriction that is checked
48 -- dynamically in this package, since the check cannot be performed at compile
49 -- time, and is relatively cheap (see body).
51 -- This package is part of the high level tasking interface used by the
52 -- compiler to expand Ada 95 tasking constructs into simpler run time calls
53 -- (aka GNARLI, GNU Ada Run-time Library Interface)
55 -- Note: the compiler generates direct calls to this interface, via Rtsfind.
56 -- Any changes to this interface may require corresponding compiler changes
57 -- in exp_ch9.adb and possibly exp_ch7.adb
59 package System
.Tasking
.Protected_Objects
.Single_Entry
is
60 pragma Elaborate_Body
;
62 ---------------------------------
63 -- Compiler Interface (GNARLI) --
64 ---------------------------------
66 -- The compiler will expand in the GNAT tree the following construct:
72 -- Open : Boolean := False;
75 -- protected body PO is
76 -- entry E when Open is
77 -- ...variable declarations...
83 -- ...variable declarations...
91 -- protected type poT is
95 -- open : boolean := false;
97 -- type poTV is limited record
98 -- open : boolean := false;
99 -- _object : aliased protection_entry;
101 -- procedure poPT__E1s (O : address; P : address; E :
102 -- protected_entry_index);
103 -- function poPT__B2s (O : address; E : protected_entry_index) return
105 -- procedure poPT__pN (_object : in out poTV);
106 -- procedure poPT__pP (_object : in out poTV);
107 -- poTA : aliased entry_body := (
108 -- barrier => poPT__B2s'unrestricted_access,
109 -- action => poPT__E1s'unrestricted_access);
111 -- procedure poTVIP (_init : in out poTV) is
113 -- _init.open := false;
114 -- object-init-proc (_init._object);
115 -- initialize_protection_entry (_init._object'unchecked_access,
116 -- unspecified_priority, _init'address, poTA'
117 -- unrestricted_access);
122 -- poTVIP (poTV!(po));
124 -- function poPT__B2s (O : address; E : protected_entry_index) return
126 -- type poTVP is access poTV;
127 -- _object : poTVP := poTVP!(O);
128 -- poR : protection_entry renames _object._object;
129 -- openP : boolean renames _object.open;
134 -- procedure poPT__E1s (O : address; P : address; E :
135 -- protected_entry_index) is
136 -- type poTVP is access poTV;
137 -- _object : poTVP := poTVP!(O);
140 -- poR : protection_entry renames _object._object;
141 -- openP : boolean renames _object.open;
142 -- ...variable declarations...
146 -- complete_single_entry_body (_object._object'unchecked_access);
149 -- when all others =>
150 -- exceptional_complete_single_entry_body (_object._object'
151 -- unchecked_access, get_gnat_exception);
155 -- procedure poPT__pN (_object : in out poTV) is
156 -- poR : protection_entry renames _object._object;
157 -- openP : boolean renames _object.open;
158 -- ...variable declarations...
164 -- procedure poPT__pP (_object : in out poTV) is
165 -- procedure _clean is
167 -- service_entry (_object._object'unchecked_access);
168 -- unlock_entry (_object._object'unchecked_access);
172 -- lock_entry (_object._object'unchecked_access);
174 -- poPT__pN (_object);
181 type Protection_Entry
is limited private;
182 -- This type contains the GNARL state of a protected object. The
183 -- application-defined portion of the state (i.e. private objects)
184 -- is maintained by the compiler-generated code.
186 type Protection_Entry_Access
is access all Protection_Entry
;
188 procedure Initialize_Protection_Entry
189 (Object
: Protection_Entry_Access
;
190 Ceiling_Priority
: Integer;
191 Compiler_Info
: System
.Address
;
192 Entry_Body
: Entry_Body_Access
);
193 -- Initialize the Object parameter so that it can be used by the run time
194 -- to keep track of the runtime state of a protected object.
196 procedure Lock_Entry
(Object
: Protection_Entry_Access
);
197 -- Lock a protected object for write access. Upon return, the caller
198 -- owns the lock to this object, and no other call to Lock or
199 -- Lock_Read_Only with the same argument will return until the
200 -- corresponding call to Unlock has been made by the caller.
202 procedure Lock_Read_Only_Entry
203 (Object
: Protection_Entry_Access
);
204 -- Lock a protected object for read access. Upon return, the caller
205 -- owns the lock for read access, and no other calls to Lock
206 -- with the same argument will return until the corresponding call
207 -- to Unlock has been made by the caller. Other cals to Lock_Read_Only
208 -- may (but need not) return before the call to Unlock, and the
209 -- corresponding callers will also own the lock for read access.
211 procedure Unlock_Entry
(Object
: Protection_Entry_Access
);
212 -- Relinquish ownership of the lock for the object represented by
213 -- the Object parameter. If this ownership was for write access, or
214 -- if it was for read access where there are no other read access
215 -- locks outstanding, one (or more, in the case of Lock_Read_Only)
216 -- of the tasks waiting on this lock (if any) will be given the
217 -- lock and allowed to return from the Lock or Lock_Read_Only call.
219 procedure Service_Entry
(Object
: Protection_Entry_Access
);
220 -- Service the entry queue of the specified object, executing the
221 -- corresponding body of any queued entry call that is waiting on True
222 -- barrier. This is used when the state of a protected object may have
223 -- changed, in particular after the execution of the statement sequence of
224 -- a protected procedure.
226 -- This must be called with abort deferred and with the corresponding
227 -- object locked. Object is unlocked on return.
229 procedure Protected_Single_Entry_Call
230 (Object
: Protection_Entry_Access
;
231 Uninterpreted_Data
: System
.Address
;
233 -- Make a protected entry call to the specified object.
234 -- Pend a protected entry call on the protected object represented
235 -- by Object. A pended call is not queued; it may be executed immediately
236 -- or queued, depending on the state of the entry barrier.
238 -- Uninterpreted_Data
239 -- This will be returned by Next_Entry_Call when this call is serviced.
240 -- It can be used by the compiler to pass information between the
241 -- caller and the server, in particular entry parameters.
244 -- The kind of call to be pended
246 procedure Timed_Protected_Single_Entry_Call
247 (Object
: Protection_Entry_Access
;
248 Uninterpreted_Data
: System
.Address
;
251 Entry_Call_Successful
: out Boolean);
252 -- Same as the Protected_Entry_Call but with time-out specified.
253 -- This routine is used to implement timed entry calls.
255 procedure Complete_Single_Entry_Body
256 (Object
: Protection_Entry_Access
);
257 pragma Inline
(Complete_Single_Entry_Body
);
258 -- Called from within an entry body procedure, indicates that the
259 -- corresponding entry call has been serviced.
261 procedure Exceptional_Complete_Single_Entry_Body
262 (Object
: Protection_Entry_Access
;
263 Ex
: Ada
.Exceptions
.Exception_Id
);
264 -- Perform all of the functions of Complete_Entry_Body. In addition,
265 -- report in Ex the exception whose propagation terminated the entry
266 -- body to the runtime system.
268 function Protected_Count_Entry
(Object
: Protection_Entry
)
270 -- Return the number of entry calls on Object (0 or 1).
272 function Protected_Single_Entry_Caller
(Object
: Protection_Entry
)
274 -- Return value of E'Caller, where E is the protected entry currently
275 -- being handled. This will only work if called from within an
276 -- entry body, as required by the LRM (C.7.1(14)).
279 type Protection_Entry
is record
280 L
: aliased Task_Primitives
.Lock
;
281 Compiler_Info
: System
.Address
;
282 Call_In_Progress
: Entry_Call_Link
;
283 Ceiling
: System
.Any_Priority
;
284 Entry_Body
: Entry_Body_Access
;
285 Entry_Queue
: Entry_Call_Link
;
288 end System
.Tasking
.Protected_Objects
.Single_Entry
;