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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT LIBRARY COMPONENTS --
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4 -- --
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5 -- A D A . C O N T A I N E R S . I N D E F I N I T E _ H O L D E R S --
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6 -- --
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7 -- B o d y --
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8 -- --
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131
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9 -- Copyright (C) 2013-2018, 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
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28 -- Note: special attention must be paid to the case of simultaneous access
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29 -- to internal shared objects and elements by different tasks. The Reference
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30 -- counter of internal shared object is the only component protected using
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31 -- atomic operations; other components and elements can be modified only when
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32 -- reference counter is equal to one (so there are no other references to this
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33 -- internal shared object and element).
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34
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35 with Ada.Unchecked_Deallocation;
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36
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37 package body Ada.Containers.Indefinite_Holders is
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38
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39 procedure Free is
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40 new Ada.Unchecked_Deallocation (Element_Type, Element_Access);
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41
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42 procedure Detach (Container : Holder);
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43 -- Detach data from shared copy if necessary. This is necessary to prepare
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44 -- container to be modified.
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45
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46 ---------
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47 -- "=" --
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48 ---------
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49
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50 function "=" (Left, Right : Holder) return Boolean is
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51 begin
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52 if Left.Reference = Right.Reference then
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53
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54 -- Covers both null and not null but the same shared object cases
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55
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56 return True;
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57
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58 elsif Left.Reference /= null and Right.Reference /= null then
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59 return Left.Reference.Element.all = Right.Reference.Element.all;
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60
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61 else
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62 return False;
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63 end if;
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64 end "=";
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65
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66 ------------
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67 -- Adjust --
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68 ------------
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69
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70 overriding procedure Adjust (Container : in out Holder) is
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71 begin
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72 if Container.Reference /= null then
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73 if Container.Busy = 0 then
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74
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75 -- Container is not locked, reuse existing internal shared object
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76
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77 Reference (Container.Reference);
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78 else
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79 -- Otherwise, create copy of both internal shared object and
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80 -- element.
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81
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82 Container.Reference :=
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83 new Shared_Holder'
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84 (Counter => <>,
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85 Element =>
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86 new Element_Type'(Container.Reference.Element.all));
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87 end if;
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88 end if;
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89
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90 Container.Busy := 0;
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91 end Adjust;
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92
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93 overriding procedure Adjust (Control : in out Reference_Control_Type) is
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94 begin
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95 if Control.Container /= null then
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96 Reference (Control.Container.Reference);
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97 Control.Container.Busy := Control.Container.Busy + 1;
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98 end if;
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99 end Adjust;
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100
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101 ------------
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102 -- Assign --
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103 ------------
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104
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105 procedure Assign (Target : in out Holder; Source : Holder) is
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106 begin
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107 if Target.Busy /= 0 then
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108 raise Program_Error with "attempt to tamper with elements";
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109 end if;
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110
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111 if Target.Reference /= Source.Reference then
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112 if Target.Reference /= null then
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113 Unreference (Target.Reference);
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114 end if;
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115
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116 Target.Reference := Source.Reference;
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117
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118 if Source.Reference /= null then
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119 Reference (Target.Reference);
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120 end if;
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121 end if;
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122 end Assign;
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123
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124 -----------
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125 -- Clear --
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126 -----------
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127
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128 procedure Clear (Container : in out Holder) is
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129 begin
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130 if Container.Busy /= 0 then
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131 raise Program_Error with "attempt to tamper with elements";
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132 end if;
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133
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134 if Container.Reference /= null then
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135 Unreference (Container.Reference);
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136 Container.Reference := null;
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137 end if;
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138 end Clear;
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139
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140 ------------------------
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141 -- Constant_Reference --
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142 ------------------------
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143
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144 function Constant_Reference
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145 (Container : aliased Holder) return Constant_Reference_Type is
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146 begin
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147 if Container.Reference = null then
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148 raise Constraint_Error with "container is empty";
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149 end if;
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150
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151 Detach (Container);
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152
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153 declare
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154 Ref : constant Constant_Reference_Type :=
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155 (Element => Container.Reference.Element.all'Access,
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156 Control => (Controlled with Container'Unrestricted_Access));
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157 begin
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158 Reference (Ref.Control.Container.Reference);
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159 Ref.Control.Container.Busy := Ref.Control.Container.Busy + 1;
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160 return Ref;
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161 end;
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162 end Constant_Reference;
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163
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164 ----------
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165 -- Copy --
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166 ----------
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167
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168 function Copy (Source : Holder) return Holder is
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169 begin
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170 if Source.Reference = null then
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171 return (Controlled with null, 0);
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172
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173 elsif Source.Busy = 0 then
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174
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175 -- Container is not locked, reuse internal shared object
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176
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177 Reference (Source.Reference);
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178
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179 return (Controlled with Source.Reference, 0);
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180
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181 else
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182 -- Otherwise, create copy of both internal shared object and element
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183
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184 return
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185 (Controlled with
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186 new Shared_Holder'
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187 (Counter => <>,
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188 Element => new Element_Type'(Source.Reference.Element.all)),
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189 0);
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190 end if;
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191 end Copy;
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192
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193 ------------
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194 -- Detach --
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195 ------------
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196
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197 procedure Detach (Container : Holder) is
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198 begin
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199 if Container.Busy = 0
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200 and then not System.Atomic_Counters.Is_One
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201 (Container.Reference.Counter)
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202 then
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203 -- Container is not locked and internal shared object is used by
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204 -- other container, create copy of both internal shared object and
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205 -- element.
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206
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207 declare
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208 Old : constant Shared_Holder_Access := Container.Reference;
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209
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210 begin
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211 Container'Unrestricted_Access.Reference :=
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212 new Shared_Holder'
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213 (Counter => <>,
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214 Element =>
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215 new Element_Type'(Container.Reference.Element.all));
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216 Unreference (Old);
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217 end;
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218 end if;
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219 end Detach;
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220
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221 -------------
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222 -- Element --
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223 -------------
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224
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225 function Element (Container : Holder) return Element_Type is
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226 begin
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227 if Container.Reference = null then
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228 raise Constraint_Error with "container is empty";
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229 else
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230 return Container.Reference.Element.all;
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231 end if;
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232 end Element;
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233
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234 --------------
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235 -- Finalize --
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236 --------------
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237
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238 overriding procedure Finalize (Container : in out Holder) is
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239 begin
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240 if Container.Busy /= 0 then
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241 raise Program_Error with "attempt to tamper with elements";
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242 end if;
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243
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244 if Container.Reference /= null then
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245 Unreference (Container.Reference);
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246 Container.Reference := null;
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247 end if;
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248 end Finalize;
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249
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250 overriding procedure Finalize (Control : in out Reference_Control_Type) is
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251 begin
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252 if Control.Container /= null then
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253 Unreference (Control.Container.Reference);
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254 Control.Container.Busy := Control.Container.Busy - 1;
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255 Control.Container := null;
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256 end if;
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257 end Finalize;
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258
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259 --------------
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260 -- Is_Empty --
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261 --------------
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262
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263 function Is_Empty (Container : Holder) return Boolean is
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264 begin
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265 return Container.Reference = null;
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266 end Is_Empty;
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267
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268 ----------
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269 -- Move --
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270 ----------
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271
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272 procedure Move (Target : in out Holder; Source : in out Holder) is
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273 begin
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274 if Target.Busy /= 0 then
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275 raise Program_Error with "attempt to tamper with elements";
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276 end if;
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277
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278 if Source.Busy /= 0 then
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279 raise Program_Error with "attempt to tamper with elements";
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280 end if;
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281
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282 if Target.Reference /= Source.Reference then
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283 if Target.Reference /= null then
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284 Unreference (Target.Reference);
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285 end if;
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286
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287 Target.Reference := Source.Reference;
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288 Source.Reference := null;
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289 end if;
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290 end Move;
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291
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292 -------------------
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293 -- Query_Element --
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294 -------------------
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295
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296 procedure Query_Element
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297 (Container : Holder;
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298 Process : not null access procedure (Element : Element_Type))
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299 is
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300 B : Natural renames Container'Unrestricted_Access.Busy;
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301
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302 begin
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303 if Container.Reference = null then
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304 raise Constraint_Error with "container is empty";
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305 end if;
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306
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307 Detach (Container);
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308
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309 B := B + 1;
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310
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311 begin
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312 Process (Container.Reference.Element.all);
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313 exception
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314 when others =>
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315 B := B - 1;
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316 raise;
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317 end;
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318
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319 B := B - 1;
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320 end Query_Element;
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321
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322 ----------
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323 -- Read --
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324 ----------
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325
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326 procedure Read
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327 (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
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328 Container : out Holder)
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329 is
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330 begin
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331 Clear (Container);
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332
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333 if not Boolean'Input (Stream) then
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334 Container.Reference :=
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335 new Shared_Holder'
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336 (Counter => <>,
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337 Element => new Element_Type'(Element_Type'Input (Stream)));
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338 end if;
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339 end Read;
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340
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341 procedure Read
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342 (Stream : not null access Root_Stream_Type'Class;
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343 Item : out Constant_Reference_Type)
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344 is
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345 begin
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346 raise Program_Error with "attempt to stream reference";
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347 end Read;
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348
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349 procedure Read
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350 (Stream : not null access Root_Stream_Type'Class;
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351 Item : out Reference_Type)
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352 is
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353 begin
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354 raise Program_Error with "attempt to stream reference";
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355 end Read;
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356
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357 ---------------
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358 -- Reference --
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359 ---------------
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360
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361 procedure Reference (Item : not null Shared_Holder_Access) is
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362 begin
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363 System.Atomic_Counters.Increment (Item.Counter);
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364 end Reference;
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365
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366 function Reference
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367 (Container : aliased in out Holder) return Reference_Type
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368 is
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369 begin
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370 if Container.Reference = null then
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371 raise Constraint_Error with "container is empty";
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372 end if;
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373
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374 Detach (Container);
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375
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376 declare
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377 Ref : constant Reference_Type :=
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378 (Element => Container.Reference.Element.all'Access,
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379 Control => (Controlled with Container'Unrestricted_Access));
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380 begin
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381 Reference (Ref.Control.Container.Reference);
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382 Ref.Control.Container.Busy := Ref.Control.Container.Busy + 1;
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383 return Ref;
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384 end;
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385 end Reference;
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386
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387 ---------------------
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388 -- Replace_Element --
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389 ---------------------
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390
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391 procedure Replace_Element
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392 (Container : in out Holder;
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393 New_Item : Element_Type)
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394 is
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395 -- Element allocator may need an accessibility check in case actual type
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396 -- is class-wide or has access discriminants (RM 4.8(10.1) and
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397 -- AI12-0035).
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398
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399 pragma Unsuppress (Accessibility_Check);
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400
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401 begin
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402 if Container.Busy /= 0 then
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403 raise Program_Error with "attempt to tamper with elements";
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404 end if;
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405
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406 if Container.Reference = null then
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407 -- Holder is empty, allocate new Shared_Holder.
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408
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409 Container.Reference :=
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410 new Shared_Holder'
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411 (Counter => <>,
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412 Element => new Element_Type'(New_Item));
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413
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414 elsif System.Atomic_Counters.Is_One (Container.Reference.Counter) then
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415 -- Shared_Holder can be reused.
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416
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417 Free (Container.Reference.Element);
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418 Container.Reference.Element := new Element_Type'(New_Item);
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419
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420 else
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421 Unreference (Container.Reference);
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422 Container.Reference :=
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423 new Shared_Holder'
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424 (Counter => <>,
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425 Element => new Element_Type'(New_Item));
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426 end if;
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427 end Replace_Element;
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428
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429 ---------------
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430 -- To_Holder --
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431 ---------------
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432
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433 function To_Holder (New_Item : Element_Type) return Holder is
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434 -- The element allocator may need an accessibility check in the case the
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435 -- actual type is class-wide or has access discriminants (RM 4.8(10.1)
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436 -- and AI12-0035).
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437
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438 pragma Unsuppress (Accessibility_Check);
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439
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440 begin
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441 return
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442 (Controlled with
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443 new Shared_Holder'
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444 (Counter => <>,
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445 Element => new Element_Type'(New_Item)), 0);
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446 end To_Holder;
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447
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448 -----------------
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449 -- Unreference --
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450 -----------------
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451
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452 procedure Unreference (Item : not null Shared_Holder_Access) is
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453
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454 procedure Free is
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455 new Ada.Unchecked_Deallocation (Shared_Holder, Shared_Holder_Access);
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456
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457 Aux : Shared_Holder_Access := Item;
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458
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459 begin
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460 if System.Atomic_Counters.Decrement (Aux.Counter) then
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461 Free (Aux.Element);
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462 Free (Aux);
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463 end if;
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464 end Unreference;
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465
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466 --------------------
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467 -- Update_Element --
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468 --------------------
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469
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470 procedure Update_Element
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471 (Container : in out Holder;
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472 Process : not null access procedure (Element : in out Element_Type))
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473 is
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|
474 B : Natural renames Container.Busy;
|
|
|
475
|
|
|
476 begin
|
|
|
477 if Container.Reference = null then
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|
|
478 raise Constraint_Error with "container is empty";
|
|
|
479 end if;
|
|
|
480
|
|
|
481 Detach (Container);
|
|
|
482
|
|
|
483 B := B + 1;
|
|
|
484
|
|
|
485 begin
|
|
|
486 Process (Container.Reference.Element.all);
|
|
|
487 exception
|
|
|
488 when others =>
|
|
|
489 B := B - 1;
|
|
|
490 raise;
|
|
|
491 end;
|
|
|
492
|
|
|
493 B := B - 1;
|
|
|
494 end Update_Element;
|
|
|
495
|
|
|
496 -----------
|
|
|
497 -- Write --
|
|
|
498 -----------
|
|
|
499
|
|
|
500 procedure Write
|
|
|
501 (Stream : not null access Ada.Streams.Root_Stream_Type'Class;
|
|
|
502 Container : Holder)
|
|
|
503 is
|
|
|
504 begin
|
|
|
505 Boolean'Output (Stream, Container.Reference = null);
|
|
|
506
|
|
|
507 if Container.Reference /= null then
|
|
|
508 Element_Type'Output (Stream, Container.Reference.Element.all);
|
|
|
509 end if;
|
|
|
510 end Write;
|
|
|
511
|
|
|
512 procedure Write
|
|
|
513 (Stream : not null access Root_Stream_Type'Class;
|
|
|
514 Item : Reference_Type)
|
|
|
515 is
|
|
|
516 begin
|
|
|
517 raise Program_Error with "attempt to stream reference";
|
|
|
518 end Write;
|
|
|
519
|
|
|
520 procedure Write
|
|
|
521 (Stream : not null access Root_Stream_Type'Class;
|
|
|
522 Item : Constant_Reference_Type)
|
|
|
523 is
|
|
|
524 begin
|
|
|
525 raise Program_Error with "attempt to stream reference";
|
|
|
526 end Write;
|
|
|
527
|
|
|
528 end Ada.Containers.Indefinite_Holders;
|
