------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                      G N A T . L O C K _ F I L E S                       --
--                                                                          --
--                                 S p e c                                  --
--                                                                          --
--           Copyright (C) 1995-2001 Ada Core Technologies, Inc.            --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- covered by the  GNU Public License.                                      --
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-- GNAT is maintained by Ada Core Technologies Inc (http://www.gnat.com).   --
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------------------------------------------------------------------------------

--  This package contains the necessary routines for using files for the
--  purpose of providing realiable system wide locking capability.

package GNAT.Lock_Files is
pragma Preelaborate;

   Lock_Error : exception;
   --  Exception raised if file cannot be locked

   subtype Path_Name is String;
   --  Pathname is used by all services provided in this unit to specified
   --  directory name and file name. On DOS based systems both directory
   --  separators are handled (i.e. slash and backslash).

   procedure Lock_File
     (Directory      : Path_Name;
      Lock_File_Name : Path_Name;
      Wait           : Duration := 1.0;
      Retries        : Natural  := Natural'Last);
   --  Create a lock file Lock_File_Name in directory Directory. If the file
   --  cannot be locked because someone already owns the lock, this procedure
   --  waits Wait seconds and retries at most Retries times. If the file
   --  still cannot be locked, Lock_Error is raised. The default is to try
   --  every second, almost forever (Natural'Last times). The full path of
   --  the file is constructed by concatenating Directory and Lock_File_Name.
   --  Directory can optionally terminate with a directory separator.

   procedure Lock_File
     (Lock_File_Name : Path_Name;
      Wait           : Duration := 1.0;
      Retries        : Natural  := Natural'Last);
   --  See above. The full lock file path is given as one string.

   procedure Unlock_File (Directory : Path_Name; Lock_File_Name : Path_Name);
   --  Unlock a file. Directory can optionally terminate with a directory
   --  separator.

   procedure Unlock_File (Lock_File_Name : Path_Name);
   --  Unlock a file whose full path is given in Lock_File_Name

end GNAT.Lock_Files;