gcc/ada/libgnat/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) 1999-2023, 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 3,  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.                                     --
  17 --                                                                          --
  18 -- As a special exception under Section 7 of GPL version 3, you are granted --
  19 -- additional permissions described in the GCC Runtime Library Exception,   --
  20 -- version 3.1, as published by the Free Software Foundation.               --
  21 --                                                                          --
  22 -- You should have received a copy of the GNU General Public License and    --
  23 -- a copy of the GCC Runtime Library Exception along with this program;     --
  24 -- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
  25 -- <http://www.gnu.org/licenses/>.                                          --
  26 --                                                                          --
  27 -- GNAT was originally developed  by the GNAT team at  New York University. --
  28 -- Extensive contributions were provided by Ada Core Technologies Inc.      --
  29 --                                                                          --
  30 ------------------------------------------------------------------------------
  31
  32 with System.Soft_Links;
  33
  34 package body System.Global_Locks is
  35
  36    type String_Access is access String;
  37
  38    Dir_Separator : Character;
  39    pragma Import (C, Dir_Separator, "__gnat_dir_separator");
  40
  41    type Lock_File_Entry is record
  42       Dir  : String_Access;
  43       File : String_Access;
  44    end record;
  45
  46    Last_Lock  : Lock_Type := Null_Lock;
  47    Lock_Table : array (Lock_Type range 1 .. 15) of Lock_File_Entry;
  48
  49    procedure Lock_File
  50      (Dir     : String;
  51       File    : String;
  52       Wait    : Duration := 0.1;
  53       Retries : Natural  := Natural'Last);
  54    --  Create a lock file File in directory Dir. If the file cannot be
  55    --  locked because someone already owns the lock, this procedure
  56    --  waits Wait seconds and retries at most Retries times. If the file
  57    --  still cannot be locked, Lock_Error is raised. The default is to try
  58    --  every second, almost forever (Natural'Last times).
  59
  60    ------------------
  61    -- Acquire_Lock --
  62    ------------------
  63
  64    procedure Acquire_Lock (Lock : in out Lock_Type) is
  65    begin
  66       Lock_File
  67         (Lock_Table (Lock).Dir.all,
  68          Lock_Table (Lock).File.all);
  69    end Acquire_Lock;
  70
  71    -----------------
  72    -- Create_Lock --
  73    -----------------
  74
  75    procedure Create_Lock (Lock : out Lock_Type; Name : String) is
  76       L : Lock_Type;
  77
  78    begin
  79       System.Soft_Links.Lock_Task.all;
  80       Last_Lock := Last_Lock + 1;
  81       L := Last_Lock;
  82       System.Soft_Links.Unlock_Task.all;
  83
  84       if L > Lock_Table'Last then
  85          raise Lock_Error;
  86       end if;
  87
  88       for J in reverse Name'Range loop
  89          if Name (J) = Dir_Separator then
  90             Lock_Table (L).Dir := new String'(Name (Name'First .. J - 1));
  91             Lock_Table (L).File := new String'(Name (J + 1 .. Name'Last));
  92             exit;
  93          end if;
  94       end loop;
  95
  96       if Lock_Table (L).Dir = null then
  97          Lock_Table (L).Dir  := new String'(".");
  98          Lock_Table (L).File := new String'(Name);
  99       end if;
 100
 101       Lock := L;
 102    end Create_Lock;
 103
 104    ---------------
 105    -- Lock_File --
 106    ---------------
 107
 108    procedure Lock_File
 109      (Dir     : String;
 110       File    : String;
 111       Wait    : Duration := 0.1;
 112       Retries : Natural  := Natural'Last)
 113    is
 114       C_Dir  : aliased String := Dir & ASCII.NUL;
 115       C_File : aliased String := File & ASCII.NUL;
 116
 117       function Try_Lock (Dir, File : System.Address) return Integer;
 118       pragma Import (C, Try_Lock, "__gnat_try_lock");
 119
 120    begin
 121       for I in 0 .. Retries loop
 122          if Try_Lock (C_Dir'Address, C_File'Address) = 1 then
 123             return;
 124          end if;
 125
 126          exit when I = Retries;
 127          delay Wait;
 128       end loop;
 129
 130       raise Lock_Error;
 131    end Lock_File;
 132
 133    ------------------
 134    -- Release_Lock --
 135    ------------------
 136
 137    procedure Release_Lock (Lock : in out Lock_Type) is
 138       S : aliased String :=
 139             Lock_Table (Lock).Dir.all & Dir_Separator &
 140             Lock_Table (Lock).File.all & ASCII.NUL;
 141
 142       procedure unlink (A : System.Address);
 143       pragma Import (C, unlink, "unlink");
 144
 145    begin
 146       unlink (S'Address);
 147    end Release_Lock;
 148
 149 end System.Global_Locks;