1 ------------------------------------------------------------------------------
3 -- GNAT COMPILER COMPONENTS --
5 -- S Y S T E M . S H A R E D _ M E M O R Y --
9 -- Copyright (C) 1998-2008, Free Software Foundation, Inc. --
11 -- GNAT 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. GNAT 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 GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
20 -- Boston, MA 02110-1301, 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 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
32 ------------------------------------------------------------------------------
34 with Ada.IO_Exceptions;
36 with Ada.Streams.Stream_IO;
38 with System.Global_Locks;
39 with System.Soft_Links;
42 with System.File_Control_Block;
46 with Ada.Unchecked_Deallocation;
47 with Ada.Unchecked_Conversion;
49 package body System.Shared_Storage is
51 package AS renames Ada.Streams;
53 package IOX renames Ada.IO_Exceptions;
55 package FCB renames System.File_Control_Block;
57 package SFI renames System.File_IO;
59 package SIO renames Ada.Streams.Stream_IO;
61 type String_Access is access String;
62 procedure Free is new Ada.Unchecked_Deallocation
63 (Object => String, Name => String_Access);
66 -- Holds the directory
68 ------------------------------------------------
69 -- Variables for Shared Variable Access Files --
70 ------------------------------------------------
72 Max_Shared_Var_Files : constant := 20;
73 -- Maximum number of lock files that can be open
75 Shared_Var_Files_Open : Natural := 0;
76 -- Number of shared variable access files currently open
78 type File_Stream_Type is new AS.Root_Stream_Type with record
81 type File_Stream_Access is access all File_Stream_Type'Class;
84 (Stream : in out File_Stream_Type;
85 Item : out AS.Stream_Element_Array;
86 Last : out AS.Stream_Element_Offset);
89 (Stream : in out File_Stream_Type;
90 Item : AS.Stream_Element_Array);
92 subtype Hash_Header is Natural range 0 .. 30;
93 -- Number of hash headers, related (for efficiency purposes only)
94 -- to the maximum number of lock files..
96 type Shared_Var_File_Entry;
97 type Shared_Var_File_Entry_Ptr is access Shared_Var_File_Entry;
99 type Shared_Var_File_Entry is record
100 Name : String_Access;
101 -- Name of variable, as passed to Read_File/Write_File routines
103 Stream : File_Stream_Access;
104 -- Stream_IO file for the shared variable file
106 Next : Shared_Var_File_Entry_Ptr;
107 Prev : Shared_Var_File_Entry_Ptr;
108 -- Links for LRU chain
111 procedure Free is new Ada.Unchecked_Deallocation
112 (Object => Shared_Var_File_Entry,
113 Name => Shared_Var_File_Entry_Ptr);
115 procedure Free is new Ada.Unchecked_Deallocation
116 (Object => File_Stream_Type'Class,
117 Name => File_Stream_Access);
119 function To_AFCB_Ptr is
120 new Ada.Unchecked_Conversion (SIO.File_Type, FCB.AFCB_Ptr);
122 LRU_Head : Shared_Var_File_Entry_Ptr;
123 LRU_Tail : Shared_Var_File_Entry_Ptr;
124 -- As lock files are opened, they are organized into a least recently
125 -- used chain, which is a doubly linked list using the Next and Prev
126 -- fields of Shared_Var_File_Entry records. The field LRU_Head points
127 -- to the least recently used entry, whose prev pointer is null, and
128 -- LRU_Tail points to the most recently used entry, whose next pointer
129 -- is null. These pointers are null only if the list is empty.
131 function Hash (F : String_Access) return Hash_Header;
132 function Equal (F1, F2 : String_Access) return Boolean;
133 -- Hash and equality functions for hash table
135 package SFT is new System.HTable.Simple_HTable
136 (Header_Num => Hash_Header,
137 Element => Shared_Var_File_Entry_Ptr,
139 Key => String_Access,
143 --------------------------------
144 -- Variables for Lock Control --
145 --------------------------------
147 Global_Lock : Global_Locks.Lock_Type;
149 Lock_Count : Natural := 0;
150 -- Counts nesting of lock calls, 0 means lock is not held
152 -----------------------
153 -- Local Subprograms --
154 -----------------------
156 procedure Initialize;
157 -- Called to initialize data structures for this package.
158 -- Has no effect except on the first call.
160 procedure Enter_SFE (SFE : Shared_Var_File_Entry_Ptr; Fname : String);
161 -- The first parameter is a pointer to a newly allocated SFE, whose
162 -- File field is already set appropriately. Fname is the name of the
163 -- variable as passed to Shared_Var_RFile/Shared_Var_WFile. Enter_SFE
164 -- completes the SFE value, and enters it into the hash table. If the
165 -- hash table is already full, the least recently used entry is first
166 -- closed and discarded.
168 function Retrieve (File : String) return Shared_Var_File_Entry_Ptr;
169 -- Given a file name, this function searches the hash table to see if
170 -- the file is currently open. If so, then a pointer to the already
171 -- created entry is returned, after first moving it to the head of
172 -- the LRU chain. If not, then null is returned.
174 function Shared_Var_ROpen (Var : String) return SIO.Stream_Access;
175 -- As described above, this routine returns null if the
176 -- corresponding shared storage does not exist, and otherwise, if
177 -- the storage does exist, a Stream_Access value that references
178 -- the shared storage, ready to read the current value.
180 function Shared_Var_WOpen (Var : String) return SIO.Stream_Access;
181 -- As described above, this routine returns a Stream_Access value
182 -- that references the shared storage, ready to write the new
183 -- value. The storage is created by this call if it does not
186 procedure Shared_Var_Close (Var : SIO.Stream_Access);
187 -- This routine signals the end of a read/assign operation. It can
188 -- be useful to embrace a read/write operation between a call to
189 -- open and a call to close which protect the whole operation.
190 -- Otherwise, two simultaneous operations can result in the
191 -- raising of exception Data_Error by setting the access mode of
192 -- the variable in an incorrect mode.
198 procedure Enter_SFE (SFE : Shared_Var_File_Entry_Ptr; Fname : String) is
199 Freed : Shared_Var_File_Entry_Ptr;
202 SFE.Name := new String'(Fname);
204 -- Release least recently used entry if we have to
206 if Shared_Var_Files_Open = Max_Shared_Var_Files then
209 if Freed.Next /= null then
210 Freed.Next.Prev := null;
213 LRU_Head := Freed.Next;
214 SFT.Remove (Freed.Name);
215 SIO.Close (Freed.Stream.File);
221 Shared_Var_Files_Open := Shared_Var_Files_Open + 1;
224 -- Add new entry to hash table
226 SFT.Set (SFE.Name, SFE);
228 -- Add new entry at end of LRU chain
230 if LRU_Head = null then
235 SFE.Prev := LRU_Tail;
236 LRU_Tail.Next := SFE;
245 function Equal (F1, F2 : String_Access) return Boolean is
247 return F1.all = F2.all;
254 function Hash (F : String_Access) return Hash_Header is
258 -- Add up characters of name, mod our table size
260 for J in F'Range loop
261 N := (N + Character'Pos (F (J))) mod (Hash_Header'Last + 1);
271 procedure Initialize is
272 procedure Get_Env_Value_Ptr (Name, Length, Ptr : Address);
273 pragma Import (C, Get_Env_Value_Ptr, "__gnat_getenv");
275 procedure Strncpy (Astring_Addr, Cstring : Address; N : Integer);
276 pragma Import (C, Strncpy, "strncpy");
278 Dir_Name : aliased constant String :=
279 "SHARED_MEMORY_DIRECTORY" & ASCII.NUL;
281 Env_Value_Ptr : aliased Address;
282 Env_Value_Length : aliased Integer;
287 (Dir_Name'Address, Env_Value_Length'Address, Env_Value_Ptr'Address);
289 Dir := new String (1 .. Env_Value_Length);
291 if Env_Value_Length > 0 then
292 Strncpy (Dir.all'Address, Env_Value_Ptr, Env_Value_Length);
295 System.Global_Locks.Create_Lock (Global_Lock, Dir.all & "__lock");
304 (Stream : in out File_Stream_Type;
305 Item : out AS.Stream_Element_Array;
306 Last : out AS.Stream_Element_Offset)
309 SIO.Read (Stream.File, Item, Last);
311 exception when others =>
319 function Retrieve (File : String) return Shared_Var_File_Entry_Ptr is
320 SFE : Shared_Var_File_Entry_Ptr;
324 SFE := SFT.Get (File'Unrestricted_Access);
328 -- Move to head of LRU chain
330 if SFE = LRU_Tail then
333 elsif SFE = LRU_Head then
334 LRU_Head := LRU_Head.Next;
335 LRU_Head.Prev := null;
338 SFE.Next.Prev := SFE.Prev;
339 SFE.Prev.Next := SFE.Next;
343 SFE.Prev := LRU_Tail;
344 LRU_Tail.Next := SFE;
351 ----------------------
352 -- Shared_Var_Close --
353 ----------------------
355 procedure Shared_Var_Close (Var : SIO.Stream_Access) is
356 pragma Warnings (Off, Var);
359 System.Soft_Links.Unlock_Task.all;
360 end Shared_Var_Close;
362 ---------------------
363 -- Shared_Var_Lock --
364 ---------------------
366 procedure Shared_Var_Lock (Var : String) is
367 pragma Warnings (Off, Var);
370 System.Soft_Links.Lock_Task.all;
373 if Lock_Count /= 0 then
374 Lock_Count := Lock_Count + 1;
375 System.Soft_Links.Unlock_Task.all;
379 System.Soft_Links.Unlock_Task.all;
380 System.Global_Locks.Acquire_Lock (Global_Lock);
385 System.Soft_Links.Unlock_Task.all;
389 ----------------------
390 -- Shared_Var_Procs --
391 ----------------------
393 package body Shared_Var_Procs is
395 use type SIO.Stream_Access;
402 S : SIO.Stream_Access := null;
404 S := Shared_Var_ROpen (Full_Name);
407 Shared_Var_Close (S);
416 S : SIO.Stream_Access := null;
418 S := Shared_Var_WOpen (Full_Name);
420 Shared_Var_Close (S);
424 end Shared_Var_Procs;
426 ----------------------
427 -- Shared_Var_ROpen --
428 ----------------------
430 function Shared_Var_ROpen (Var : String) return SIO.Stream_Access is
431 SFE : Shared_Var_File_Entry_Ptr;
433 use type Ada.Streams.Stream_IO.File_Mode;
436 System.Soft_Links.Lock_Task.all;
437 SFE := Retrieve (Var);
439 -- Here if file is not already open, try to open it
443 S : aliased constant String := Dir.all & Var;
446 SFE := new Shared_Var_File_Entry;
447 SFE.Stream := new File_Stream_Type;
448 SIO.Open (SFE.Stream.File, SIO.In_File, Name => S);
449 SFI.Make_Unbuffered (To_AFCB_Ptr (SFE.Stream.File));
451 -- File opened successfully, put new entry in hash table. Note
452 -- that in this case, file is positioned correctly for read.
454 Enter_SFE (SFE, Var);
457 -- If we get an exception, it means that the file does not
458 -- exist, and in this case, we don't need the SFE and we
461 when IOX.Name_Error =>
463 System.Soft_Links.Unlock_Task.all;
467 -- Here if file is already open, set file for reading
470 if SIO.Mode (SFE.Stream.File) /= SIO.In_File then
471 SIO.Set_Mode (SFE.Stream.File, SIO.In_File);
472 SFI.Make_Unbuffered (To_AFCB_Ptr (SFE.Stream.File));
475 SIO.Set_Index (SFE.Stream.File, 1);
478 return SIO.Stream_Access (SFE.Stream);
482 System.Soft_Links.Unlock_Task.all;
484 end Shared_Var_ROpen;
486 -----------------------
487 -- Shared_Var_Unlock --
488 -----------------------
490 procedure Shared_Var_Unlock (Var : String) is
491 pragma Warnings (Off, Var);
494 System.Soft_Links.Lock_Task.all;
496 Lock_Count := Lock_Count - 1;
498 if Lock_Count = 0 then
499 System.Global_Locks.Release_Lock (Global_Lock);
501 System.Soft_Links.Unlock_Task.all;
505 System.Soft_Links.Unlock_Task.all;
507 end Shared_Var_Unlock;
509 ---------------------
510 -- Share_Var_WOpen --
511 ---------------------
513 function Shared_Var_WOpen (Var : String) return SIO.Stream_Access is
514 SFE : Shared_Var_File_Entry_Ptr;
516 use type Ada.Streams.Stream_IO.File_Mode;
519 System.Soft_Links.Lock_Task.all;
520 SFE := Retrieve (Var);
524 S : aliased constant String := Dir.all & Var;
527 SFE := new Shared_Var_File_Entry;
528 SFE.Stream := new File_Stream_Type;
529 SIO.Open (SFE.Stream.File, SIO.Out_File, Name => S);
530 SFI.Make_Unbuffered (To_AFCB_Ptr (SFE.Stream.File));
533 -- If we get an exception, it means that the file does not
534 -- exist, and in this case, we create the file.
536 when IOX.Name_Error =>
539 SIO.Create (SFE.Stream.File, SIO.Out_File, Name => S);
542 -- Error if we cannot create the file
545 raise Program_Error with
546 "Cannot create shared variable file for """ & S & '"';
550 -- Make new hash table entry for opened/created file. Note that
551 -- in both cases, the file is already in write mode at the start
552 -- of the file, ready to be written.
554 Enter_SFE (SFE, Var);
556 -- Here if file is already open, set file for writing
559 if SIO.Mode (SFE.Stream.File) /= SIO.Out_File then
560 SIO.Set_Mode (SFE.Stream.File, SIO.Out_File);
561 SFI.Make_Unbuffered (To_AFCB_Ptr (SFE.Stream.File));
564 SIO.Set_Index (SFE.Stream.File, 1);
567 return SIO.Stream_Access (SFE.Stream);
571 System.Soft_Links.Unlock_Task.all;
573 end Shared_Var_WOpen;
580 (Stream : in out File_Stream_Type;
581 Item : AS.Stream_Element_Array)
584 SIO.Write (Stream.File, Item);
587 end System.Shared_Storage;