gcc/ada/s-gloloc.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT COMPILER COMPONENTS                         --
   4 --                                                                          --
   5 --                  S Y S T E M . G L O B A L _ L O C K S                   --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --          Copyright (C) 1999-2001 Free Software Foundation, Inc.          --
  10 --                                                                          --
  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,  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 --                                                                          --
  29 -- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com).   --
  30 --                                                                          --
  31 ------------------------------------------------------------------------------
  32
  33 with GNAT.Task_Lock;
  34
  35 package body System.Global_Locks is
  36
  37    type String_Access is access String;
  38
  39    package TSL renames GNAT.Task_Lock;
  40
  41    Dir_Separator : Character;
  42    pragma Import (C, Dir_Separator, "__gnat_dir_separator");
  43
  44    type Lock_File_Entry is record
  45       Dir  : String_Access;
  46       File : String_Access;
  47    end record;
  48
  49    Last_Lock  : Lock_Type := Null_Lock;
  50    Lock_Table : array (Lock_Type range 1 .. 15) of Lock_File_Entry;
  51
  52    procedure Lock_File
  53      (Dir     : String;
  54       File    : String;
  55       Wait    : Duration := 0.1;
  56       Retries : Natural  := Natural'Last);
  57    --  Create a lock file File in directory Dir. If the file  cannot be
  58    --  locked because someone already owns the lock, this procedure
  59    --  waits Wait seconds and retries at most Retries times. If the file
  60    --  still cannot be locked, Lock_Error is raised. The default is to try
  61    --  every second, almost forever (Natural'Last times).
  62
  63    ------------------
  64    -- Acquire_Lock --
  65    ------------------
  66
  67    procedure Acquire_Lock
  68      (Lock : in out Lock_Type) is
  69    begin
  70       Lock_File
  71         (Lock_Table (Lock).Dir.all,
  72          Lock_Table (Lock).File.all);
  73    end Acquire_Lock;
  74
  75    -----------------
  76    -- Create_Lock --
  77    -----------------
  78
  79    procedure Create_Lock
  80      (Lock : out Lock_Type;
  81       Name : in String)
  82    is
  83       L : Lock_Type;
  84
  85    begin
  86       TSL.Lock;
  87       Last_Lock := Last_Lock + 1;
  88       L := Last_Lock;
  89       TSL.Unlock;
  90
  91       if L > Lock_Table'Last then
  92          raise Lock_Error;
  93       end if;
  94
  95       for J in reverse Name'Range loop
  96          if Name (J) = Dir_Separator then
  97             Lock_Table (L).Dir
  98               := new String'(Name (Name'First .. J - 1));
  99             Lock_Table (L).File
 100               := new String'(Name (J + 1 .. Name'Last));
 101             exit;
 102          end if;
 103       end loop;
 104
 105       if Lock_Table (L).Dir = null then
 106          Lock_Table (L).Dir  := new String'(".");
 107          Lock_Table (L).File := new String'(Name);
 108       end if;
 109
 110       Lock := L;
 111    end Create_Lock;
 112
 113    ---------------
 114    -- Lock_File --
 115    ---------------
 116
 117    procedure Lock_File
 118      (Dir     : String;
 119       File    : String;
 120       Wait    : Duration := 0.1;
 121       Retries : Natural  := Natural'Last)
 122    is
 123       C_Dir  : aliased String := Dir & ASCII.NUL;
 124       C_File : aliased String := File & ASCII.NUL;
 125
 126       function Try_Lock (Dir, File : System.Address) return Integer;
 127       pragma Import (C, Try_Lock, "__gnat_try_lock");
 128
 129    begin
 130       for I in 0 .. Retries loop
 131          if Try_Lock (C_Dir'Address, C_File'Address) = 1 then
 132             return;
 133          end if;
 134          exit when I = Retries;
 135          delay Wait;
 136       end loop;
 137       raise Lock_Error;
 138    end Lock_File;
 139
 140    ------------------
 141    -- Release_Lock --
 142    ------------------
 143
 144    procedure Release_Lock
 145      (Lock : in out Lock_Type)
 146    is
 147       S : aliased String :=
 148         Lock_Table (Lock).Dir.all & Dir_Separator &
 149         Lock_Table (Lock).File.all & ASCII.NUL;
 150
 151       procedure unlink (A : System.Address);
 152       pragma Import (C, unlink, "unlink");
 153
 154    begin
 155       unlink (S'Address);
 156    end Release_Lock;
 157
 158 end System.Global_Locks;