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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- S Y S T E M . G L O B A L _ L O C K S --
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6 -- --
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7 -- B o d y --
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8 -- --
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145
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9 -- Copyright (C) 1999-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 with System.Soft_Links;
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33
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34 package body System.Global_Locks is
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35
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36 type String_Access is access String;
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37
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38 Dir_Separator : Character;
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39 pragma Import (C, Dir_Separator, "__gnat_dir_separator");
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40
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41 type Lock_File_Entry is record
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42 Dir : String_Access;
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43 File : String_Access;
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44 end record;
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45
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46 Last_Lock : Lock_Type := Null_Lock;
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47 Lock_Table : array (Lock_Type range 1 .. 15) of Lock_File_Entry;
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48
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49 procedure Lock_File
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50 (Dir : String;
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51 File : String;
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52 Wait : Duration := 0.1;
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53 Retries : Natural := Natural'Last);
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54 -- Create a lock file File in directory Dir. If the file cannot be
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55 -- locked because someone already owns the lock, this procedure
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56 -- waits Wait seconds and retries at most Retries times. If the file
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57 -- still cannot be locked, Lock_Error is raised. The default is to try
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58 -- every second, almost forever (Natural'Last times).
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59
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60 ------------------
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61 -- Acquire_Lock --
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62 ------------------
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63
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64 procedure Acquire_Lock (Lock : in out Lock_Type) is
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65 begin
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66 Lock_File
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67 (Lock_Table (Lock).Dir.all,
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68 Lock_Table (Lock).File.all);
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69 end Acquire_Lock;
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70
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71 -----------------
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72 -- Create_Lock --
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73 -----------------
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74
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75 procedure Create_Lock (Lock : out Lock_Type; Name : String) is
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76 L : Lock_Type;
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77
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78 begin
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79 System.Soft_Links.Lock_Task.all;
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80 Last_Lock := Last_Lock + 1;
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81 L := Last_Lock;
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82 System.Soft_Links.Unlock_Task.all;
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83
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84 if L > Lock_Table'Last then
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85 raise Lock_Error;
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86 end if;
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87
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88 for J in reverse Name'Range loop
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89 if Name (J) = Dir_Separator then
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90 Lock_Table (L).Dir := new String'(Name (Name'First .. J - 1));
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91 Lock_Table (L).File := new String'(Name (J + 1 .. Name'Last));
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92 exit;
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93 end if;
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94 end loop;
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95
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96 if Lock_Table (L).Dir = null then
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97 Lock_Table (L).Dir := new String'(".");
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98 Lock_Table (L).File := new String'(Name);
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99 end if;
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100
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101 Lock := L;
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102 end Create_Lock;
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103
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104 ---------------
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105 -- Lock_File --
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106 ---------------
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107
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108 procedure Lock_File
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109 (Dir : String;
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110 File : String;
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111 Wait : Duration := 0.1;
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112 Retries : Natural := Natural'Last)
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113 is
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114 C_Dir : aliased String := Dir & ASCII.NUL;
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115 C_File : aliased String := File & ASCII.NUL;
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116
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117 function Try_Lock (Dir, File : System.Address) return Integer;
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118 pragma Import (C, Try_Lock, "__gnat_try_lock");
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119
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120 begin
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121 for I in 0 .. Retries loop
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122 if Try_Lock (C_Dir'Address, C_File'Address) = 1 then
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123 return;
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124 end if;
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125
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126 exit when I = Retries;
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127 delay Wait;
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128 end loop;
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129
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130 raise Lock_Error;
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131 end Lock_File;
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132
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133 ------------------
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134 -- Release_Lock --
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135 ------------------
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136
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137 procedure Release_Lock (Lock : in out Lock_Type) is
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138 S : aliased String :=
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139 Lock_Table (Lock).Dir.all & Dir_Separator &
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140 Lock_Table (Lock).File.all & ASCII.NUL;
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141
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142 procedure unlink (A : System.Address);
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143 pragma Import (C, unlink, "unlink");
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144
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145 begin
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146 unlink (S'Address);
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147 end Release_Lock;
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148
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149 end System.Global_Locks;
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