1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                      G N A T . L O C K _ F I L E S                       --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--                     Copyright (C) 1995-2019, AdaCore                     --
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--  This package contains the necessary routines for using files for the
33--  purpose of providing reliable system wide locking capability.
34
35package GNAT.Lock_Files is
36   pragma Preelaborate;
37
38   Lock_Error : exception;
39   --  Exception raised if file cannot be locked
40
41   subtype Path_Name is String;
42   --  Pathname is used by all services provided in this unit to specify
43   --  directory name and file name. On DOS based systems both directory
44   --  separators are handled (i.e. slash and backslash).
45
46   procedure Lock_File
47     (Directory      : Path_Name;
48      Lock_File_Name : Path_Name;
49      Wait           : Duration := 1.0;
50      Retries        : Natural  := Natural'Last);
51   --  Create a lock file Lock_File_Name in directory Directory. If the file
52   --  cannot be locked because someone already owns the lock, this procedure
53   --  waits Wait seconds and retries at most Retries times. If the file
54   --  still cannot be locked, Lock_Error is raised. The default is to try
55   --  every second, almost forever (Natural'Last times). The full path of
56   --  the file is constructed by concatenating Directory and Lock_File_Name.
57   --  Directory can optionally terminate with a directory separator.
58
59   procedure Lock_File
60     (Lock_File_Name : Path_Name;
61      Wait           : Duration := 1.0;
62      Retries        : Natural  := Natural'Last);
63   --  See above. The full lock file path is given as one string
64
65   procedure Unlock_File (Directory : Path_Name; Lock_File_Name : Path_Name);
66   --  Unlock a file. Directory can optionally terminate with a directory
67   --  separator.
68
69   procedure Unlock_File (Lock_File_Name : Path_Name);
70   --  Unlock a file whose full path is given in Lock_File_Name
71
72end GNAT.Lock_Files;
73