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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 -- ADA.CONTAINERS.HASH_TABLES.GENERIC_KEYS --
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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) 2004-2018, 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 -- This unit was originally developed by Matthew J Heaney. --
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28 ------------------------------------------------------------------------------
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29
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30 package body Ada.Containers.Hash_Tables.Generic_Keys is
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31
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32 pragma Warnings (Off, "variable ""Busy*"" is not referenced");
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33 pragma Warnings (Off, "variable ""Lock*"" is not referenced");
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34 -- See comment in Ada.Containers.Helpers
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35
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36 -----------------------------
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37 -- Checked_Equivalent_Keys --
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38 -----------------------------
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39
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40 function Checked_Equivalent_Keys
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41 (HT : aliased in out Hash_Table_Type;
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42 Key : Key_Type;
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43 Node : Node_Access) return Boolean
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44 is
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45 Lock : With_Lock (HT.TC'Unrestricted_Access);
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46 begin
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47 return Equivalent_Keys (Key, Node);
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48 end Checked_Equivalent_Keys;
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49
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50 -------------------
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51 -- Checked_Index --
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52 -------------------
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53
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54 function Checked_Index
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55 (HT : aliased in out Hash_Table_Type;
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56 Key : Key_Type) return Hash_Type
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57 is
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58 Lock : With_Lock (HT.TC'Unrestricted_Access);
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59 begin
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60 return Hash (Key) mod HT.Buckets'Length;
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61 end Checked_Index;
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62
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63 --------------------------
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64 -- Delete_Key_Sans_Free --
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65 --------------------------
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66
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67 procedure Delete_Key_Sans_Free
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68 (HT : in out Hash_Table_Type;
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69 Key : Key_Type;
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70 X : out Node_Access)
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71 is
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72 Indx : Hash_Type;
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73 Prev : Node_Access;
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74
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75 begin
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76 if HT.Length = 0 then
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77 X := null;
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78 return;
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79 end if;
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80
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81 -- Per AI05-0022, the container implementation is required to detect
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82 -- element tampering by a generic actual subprogram.
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83
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84 TC_Check (HT.TC);
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85
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86 Indx := Checked_Index (HT, Key);
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87 X := HT.Buckets (Indx);
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88
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89 if X = null then
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90 return;
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91 end if;
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92
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93 if Checked_Equivalent_Keys (HT, Key, X) then
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94 TC_Check (HT.TC);
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95 HT.Buckets (Indx) := Next (X);
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96 HT.Length := HT.Length - 1;
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97 return;
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98 end if;
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99
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100 loop
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101 Prev := X;
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102 X := Next (Prev);
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103
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104 if X = null then
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105 return;
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106 end if;
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107
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108 if Checked_Equivalent_Keys (HT, Key, X) then
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109 TC_Check (HT.TC);
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110 Set_Next (Node => Prev, Next => Next (X));
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111 HT.Length := HT.Length - 1;
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112 return;
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113 end if;
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114 end loop;
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115 end Delete_Key_Sans_Free;
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116
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117 ----------
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118 -- Find --
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119 ----------
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120
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121 function Find
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122 (HT : aliased in out Hash_Table_Type;
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123 Key : Key_Type) return Node_Access
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124 is
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125 Indx : Hash_Type;
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126 Node : Node_Access;
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127
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128 begin
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129 if HT.Length = 0 then
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130 return null;
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131 end if;
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132
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133 Indx := Checked_Index (HT, Key);
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134
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135 Node := HT.Buckets (Indx);
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136 while Node /= null loop
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137 if Checked_Equivalent_Keys (HT, Key, Node) then
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138 return Node;
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139 end if;
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140 Node := Next (Node);
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141 end loop;
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142
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143 return null;
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144 end Find;
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145
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146 --------------------------------
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147 -- Generic_Conditional_Insert --
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148 --------------------------------
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149
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150 procedure Generic_Conditional_Insert
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151 (HT : in out Hash_Table_Type;
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152 Key : Key_Type;
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153 Node : out Node_Access;
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154 Inserted : out Boolean)
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155 is
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156 Indx : Hash_Type;
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157
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158 begin
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159 -- Per AI05-0022, the container implementation is required to detect
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160 -- element tampering by a generic actual subprogram.
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161
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162 TC_Check (HT.TC);
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163
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164 Indx := Checked_Index (HT, Key);
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165 Node := HT.Buckets (Indx);
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166
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167 if Node = null then
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168 if Checks and then HT.Length = Count_Type'Last then
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169 raise Constraint_Error;
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170 end if;
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171
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172 Node := New_Node (Next => null);
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173 Inserted := True;
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174
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175 HT.Buckets (Indx) := Node;
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176 HT.Length := HT.Length + 1;
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177
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178 return;
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179 end if;
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180
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181 loop
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182 if Checked_Equivalent_Keys (HT, Key, Node) then
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183 Inserted := False;
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184 return;
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185 end if;
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186
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187 Node := Next (Node);
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188
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189 exit when Node = null;
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190 end loop;
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191
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192 if Checks and then HT.Length = Count_Type'Last then
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193 raise Constraint_Error;
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194 end if;
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195
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196 Node := New_Node (Next => HT.Buckets (Indx));
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197 Inserted := True;
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198
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199 HT.Buckets (Indx) := Node;
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200 HT.Length := HT.Length + 1;
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201 end Generic_Conditional_Insert;
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202
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203 -----------------------------
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204 -- Generic_Replace_Element --
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205 -----------------------------
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206
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207 procedure Generic_Replace_Element
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208 (HT : in out Hash_Table_Type;
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209 Node : Node_Access;
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210 Key : Key_Type)
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211 is
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212 pragma Assert (HT.Length > 0);
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213 pragma Assert (Node /= null);
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214
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215 Old_Indx : Hash_Type;
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216 New_Indx : constant Hash_Type := Checked_Index (HT, Key);
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217
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218 New_Bucket : Node_Access renames HT.Buckets (New_Indx);
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219 N, M : Node_Access;
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220
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221 begin
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222 -- Per AI05-0022, the container implementation is required to detect
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223 -- element tampering by a generic actual subprogram.
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224
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225 declare
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226 Lock : With_Lock (HT.TC'Unrestricted_Access);
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227 begin
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228 Old_Indx := Hash (Node) mod HT.Buckets'Length;
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229 end;
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230
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231 if Checked_Equivalent_Keys (HT, Key, Node) then
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232 TE_Check (HT.TC);
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233
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234 -- We can change a node's key to Key (that's what Assign is for), but
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235 -- only if Key is not already in the hash table. (In a unique-key
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236 -- hash table as this one a key is mapped to exactly one node only.)
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237 -- The exception is when Key is mapped to Node, in which case the
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238 -- change is allowed.
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239
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240 Assign (Node, Key);
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241 return;
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242 end if;
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243
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244 -- Key is not equivalent to Node, so we now have to determine if it's
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245 -- equivalent to some other node in the hash table. This is the case
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246 -- irrespective of whether Key is in the same or a different bucket from
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247 -- Node.
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248
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249 N := New_Bucket;
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250 while N /= null loop
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251 if Checks and then Checked_Equivalent_Keys (HT, Key, N) then
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252 pragma Assert (N /= Node);
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253 raise Program_Error with
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254 "attempt to replace existing element";
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255 end if;
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256
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257 N := Next (N);
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258 end loop;
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259
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260 -- We have determined that Key is not already in the hash table, so
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261 -- the change is tentatively allowed. We now perform the standard
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262 -- checks to determine whether the hash table is locked (because you
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263 -- cannot change an element while it's in use by Query_Element or
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264 -- Update_Element), or if the container is busy (because moving a
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265 -- node to a different bucket would interfere with iteration).
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266
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267 if Old_Indx = New_Indx then
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268 -- The node is already in the bucket implied by Key. In this case
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269 -- we merely change its value without moving it.
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270
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271 TE_Check (HT.TC);
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272
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273 Assign (Node, Key);
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274 return;
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275 end if;
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276
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277 -- The node is a bucket different from the bucket implied by Key
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278
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279 TC_Check (HT.TC);
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280
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281 -- Do the assignment first, before moving the node, so that if Assign
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282 -- propagates an exception, then the hash table will not have been
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283 -- modified (except for any possible side-effect Assign had on Node).
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284
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285 Assign (Node, Key);
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286
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287 -- Now we can safely remove the node from its current bucket
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288
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289 N := HT.Buckets (Old_Indx);
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290 pragma Assert (N /= null);
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291
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292 if N = Node then
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293 HT.Buckets (Old_Indx) := Next (Node);
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294
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295 else
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296 pragma Assert (HT.Length > 1);
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297
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298 loop
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299 M := Next (N);
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300 pragma Assert (M /= null);
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301
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302 if M = Node then
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303 Set_Next (Node => N, Next => Next (Node));
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304 exit;
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305 end if;
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306
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307 N := M;
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308 end loop;
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309 end if;
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310
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311 -- Now we link the node into its new bucket (corresponding to Key)
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312
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313 Set_Next (Node => Node, Next => New_Bucket);
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314 New_Bucket := Node;
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315 end Generic_Replace_Element;
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316
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317 -----------
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318 -- Index --
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319 -----------
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320
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321 function Index
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322 (HT : Hash_Table_Type;
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323 Key : Key_Type) return Hash_Type
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324 is
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325 begin
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326 return Hash (Key) mod HT.Buckets'Length;
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327 end Index;
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328
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329 end Ada.Containers.Hash_Tables.Generic_Keys;
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