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) 1999-2008, 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,  51  Franklin  Street,  Fifth  Floor, --
  20 -- Boston, MA 02110-1301, 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 was originally developed  by the GNAT team at  New York University. --
  30 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  31 --                                                                          --
  32 ------------------------------------------------------------------------------
  33
  34 with System.Soft_Links;
  35
  36 package body System.Global_Locks is
  37
  38    type String_Access is access String;
  39
  40    Dir_Separator : Character;
  41    pragma Import (C, Dir_Separator, "__gnat_dir_separator");
  42
  43    type Lock_File_Entry is record
  44       Dir  : String_Access;
  45       File : String_Access;
  46    end record;
  47
  48    Last_Lock  : Lock_Type := Null_Lock;
  49    Lock_Table : array (Lock_Type range 1 .. 15) of Lock_File_Entry;
  50
  51    procedure Lock_File
  52      (Dir     : String;
  53       File    : String;
  54       Wait    : Duration := 0.1;
  55       Retries : Natural  := Natural'Last);
  56    --  Create a lock file File in directory Dir. If the file  cannot be
  57    --  locked because someone already owns the lock, this procedure
  58    --  waits Wait seconds and retries at most Retries times. If the file
  59    --  still cannot be locked, Lock_Error is raised. The default is to try
  60    --  every second, almost forever (Natural'Last times).
  61
  62    ------------------
  63    -- Acquire_Lock --
  64    ------------------
  65
  66    procedure Acquire_Lock (Lock : in out Lock_Type) is
  67    begin
  68       Lock_File
  69         (Lock_Table (Lock).Dir.all,
  70          Lock_Table (Lock).File.all);
  71    end Acquire_Lock;
  72
  73    -----------------
  74    -- Create_Lock --
  75    -----------------
  76
  77    procedure Create_Lock (Lock : out Lock_Type; Name : String) is
  78       L : Lock_Type;
  79
  80    begin
  81       System.Soft_Links.Lock_Task.all;
  82       Last_Lock := Last_Lock + 1;
  83       L := Last_Lock;
  84       System.Soft_Links.Unlock_Task.all;
  85
  86       if L > Lock_Table'Last then
  87          raise Lock_Error;
  88       end if;
  89
  90       for J in reverse Name'Range loop
  91          if Name (J) = Dir_Separator then
  92             Lock_Table (L).Dir := new String'(Name (Name'First .. J - 1));
  93             Lock_Table (L).File := new String'(Name (J + 1 .. Name'Last));
  94             exit;
  95          end if;
  96       end loop;
  97
  98       if Lock_Table (L).Dir = null then
  99          Lock_Table (L).Dir  := new String'(".");
 100          Lock_Table (L).File := new String'(Name);
 101       end if;
 102
 103       Lock := L;
 104    end Create_Lock;
 105
 106    ---------------
 107    -- Lock_File --
 108    ---------------
 109
 110    procedure Lock_File
 111      (Dir     : String;
 112       File    : String;
 113       Wait    : Duration := 0.1;
 114       Retries : Natural  := Natural'Last)
 115    is
 116       C_Dir  : aliased String := Dir & ASCII.NUL;
 117       C_File : aliased String := File & ASCII.NUL;
 118
 119       function Try_Lock (Dir, File : System.Address) return Integer;
 120       pragma Import (C, Try_Lock, "__gnat_try_lock");
 121
 122    begin
 123       for I in 0 .. Retries loop
 124          if Try_Lock (C_Dir'Address, C_File'Address) = 1 then
 125             return;
 126          end if;
 127
 128          exit when I = Retries;
 129          delay Wait;
 130       end loop;
 131
 132       raise Lock_Error;
 133    end Lock_File;
 134
 135    ------------------
 136    -- Release_Lock --
 137    ------------------
 138
 139    procedure Release_Lock (Lock : in out Lock_Type) is
 140       S : aliased String :=
 141             Lock_Table (Lock).Dir.all & Dir_Separator &
 142             Lock_Table (Lock).File.all & ASCII.NUL;
 143
 144       procedure unlink (A : System.Address);
 145       pragma Import (C, unlink, "unlink");
 146
 147    begin
 148       unlink (S'Address);
 149    end Release_Lock;
 150
 151 end System.Global_Locks;