File : 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) 1999-2015, 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 -- --
19 -- --
20 -- --
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;