------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                      G N A T . L O C K _ F I L E S                       --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--          Copyright (C) 1998-2019, Free Software Foundation, Inc.         --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
--                                                                          --
-- As a special exception under Section 7 of GPL version 3, you are granted --
-- additional permissions described in the GCC Runtime Library Exception,   --
-- version 3.1, as published by the Free Software Foundation.               --
--                                                                          --
-- You should have received a copy of the GNU General Public License and    --
-- a copy of the GCC Runtime Library Exception along with this program;     --
-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
-- <http://www.gnu.org/licenses/>.                                          --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------

with System;

package body GNAT.Lock_Files is

   Dir_Separator : Character;
   pragma Import (C, Dir_Separator, "__gnat_dir_separator");

   ---------------
   -- Lock_File --
   ---------------

   procedure Lock_File
     (Directory      : Path_Name;
      Lock_File_Name : Path_Name;
      Wait           : Duration := 1.0;
      Retries        : Natural  := Natural'Last)
   is
      Dir  : aliased String := Directory & ASCII.NUL;
      File : aliased String := Lock_File_Name & ASCII.NUL;

      function Try_Lock (Dir, File : System.Address) return Integer;
      pragma Import (C, Try_Lock, "__gnat_try_lock");

   begin
      --  If a directory separator was provided, just remove the one we have
      --  added above.

      if Directory (Directory'Last) = Dir_Separator
        or else Directory (Directory'Last) = '/'
      then
         Dir (Dir'Last - 1) := ASCII.NUL;
      end if;

      --  Try to lock the file Retries times

      for I in 0 .. Retries loop
         if Try_Lock (Dir'Address, File'Address) = 1 then
            return;
         end if;

         exit when I = Retries;
         delay Wait;
      end loop;

      raise Lock_Error;
   end Lock_File;

   ---------------
   -- Lock_File --
   ---------------

   procedure Lock_File
     (Lock_File_Name : Path_Name;
      Wait           : Duration := 1.0;
      Retries        : Natural  := Natural'Last)
   is
   begin
      for J in reverse Lock_File_Name'Range loop
         if Lock_File_Name (J) = Dir_Separator
           or else Lock_File_Name (J) = '/'
         then
            Lock_File
              (Lock_File_Name (Lock_File_Name'First .. J - 1),
               Lock_File_Name (J + 1 .. Lock_File_Name'Last),
               Wait,
               Retries);
            return;
         end if;
      end loop;

      Lock_File (".", Lock_File_Name, Wait, Retries);
   end Lock_File;

   -----------------
   -- Unlock_File --
   -----------------

   procedure Unlock_File (Lock_File_Name : Path_Name) is
      S : aliased String := Lock_File_Name & ASCII.NUL;

      procedure unlink (A : System.Address);
      pragma Import (C, unlink, "unlink");

   begin
      unlink (S'Address);
   end Unlock_File;

   -----------------
   -- Unlock_File --
   -----------------

   procedure Unlock_File (Directory : Path_Name; Lock_File_Name : Path_Name) is
   begin
      if Directory (Directory'Last) = Dir_Separator
        or else Directory (Directory'Last) = '/'
      then
         Unlock_File (Directory & Lock_File_Name);
      else
         Unlock_File (Directory & Dir_Separator & Lock_File_Name);
      end if;
   end Unlock_File;

end GNAT.Lock_Files;
