1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
|
------------------------------------------------------------------------------
-- --
-- GNAT COMPILER COMPONENTS --
-- --
-- S Y S T E M . G L O B A L _ L O C K S --
-- --
-- B o d y --
-- --
-- Copyright (C) 1999-2018, 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.Soft_Links;
package body System.Global_Locks is
type String_Access is access String;
Dir_Separator : Character;
pragma Import (C, Dir_Separator, "__gnat_dir_separator");
type Lock_File_Entry is record
Dir : String_Access;
File : String_Access;
end record;
Last_Lock : Lock_Type := Null_Lock;
Lock_Table : array (Lock_Type range 1 .. 15) of Lock_File_Entry;
procedure Lock_File
(Dir : String;
File : String;
Wait : Duration := 0.1;
Retries : Natural := Natural'Last);
-- Create a lock file File in directory Dir. 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).
------------------
-- Acquire_Lock --
------------------
procedure Acquire_Lock (Lock : in out Lock_Type) is
begin
Lock_File
(Lock_Table (Lock).Dir.all,
Lock_Table (Lock).File.all);
end Acquire_Lock;
-----------------
-- Create_Lock --
-----------------
procedure Create_Lock (Lock : out Lock_Type; Name : String) is
L : Lock_Type;
begin
System.Soft_Links.Lock_Task.all;
Last_Lock := Last_Lock + 1;
L := Last_Lock;
System.Soft_Links.Unlock_Task.all;
if L > Lock_Table'Last then
raise Lock_Error;
end if;
for J in reverse Name'Range loop
if Name (J) = Dir_Separator then
Lock_Table (L).Dir := new String'(Name (Name'First .. J - 1));
Lock_Table (L).File := new String'(Name (J + 1 .. Name'Last));
exit;
end if;
end loop;
if Lock_Table (L).Dir = null then
Lock_Table (L).Dir := new String'(".");
Lock_Table (L).File := new String'(Name);
end if;
Lock := L;
end Create_Lock;
---------------
-- Lock_File --
---------------
procedure Lock_File
(Dir : String;
File : String;
Wait : Duration := 0.1;
Retries : Natural := Natural'Last)
is
C_Dir : aliased String := Dir & ASCII.NUL;
C_File : aliased String := File & ASCII.NUL;
function Try_Lock (Dir, File : System.Address) return Integer;
pragma Import (C, Try_Lock, "__gnat_try_lock");
begin
for I in 0 .. Retries loop
if Try_Lock (C_Dir'Address, C_File'Address) = 1 then
return;
end if;
exit when I = Retries;
delay Wait;
end loop;
raise Lock_Error;
end Lock_File;
------------------
-- Release_Lock --
------------------
procedure Release_Lock (Lock : in out Lock_Type) is
S : aliased String :=
Lock_Table (Lock).Dir.all & Dir_Separator &
Lock_Table (Lock).File.all & ASCII.NUL;
procedure unlink (A : System.Address);
pragma Import (C, unlink, "unlink");
begin
unlink (S'Address);
end Release_Lock;
end System.Global_Locks;
|
