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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 -- T A B L E --
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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) 1992-2018, 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 -- 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 Debug; use Debug;
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33 with Opt; use Opt;
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34 with Output; use Output;
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35 with System; use System;
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36 with Tree_IO; use Tree_IO;
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37
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38 with System.Memory; use System.Memory;
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39
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40 with Unchecked_Conversion;
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41
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42 pragma Elaborate_All (Output);
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43
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44 package body Table is
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45 package body Table is
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46
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47 Min : constant Int := Int (Table_Low_Bound);
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48 -- Subscript of the minimum entry in the currently allocated table
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49
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50 Length : Int := 0;
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51 -- Number of entries in currently allocated table. The value of zero
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52 -- ensures that we initially allocate the table.
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53
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54 -----------------------
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55 -- Local Subprograms --
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56 -----------------------
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57
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58 procedure Reallocate;
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59 -- Reallocate the existing table according to the current value stored
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60 -- in Max. Works correctly to do an initial allocation if the table
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61 -- is currently null.
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62
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63 function Tree_Get_Table_Address return Address;
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64 -- Return Null_Address if the table length is zero,
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65 -- Table (First)'Address if not.
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66
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67 pragma Warnings (Off);
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68 -- Turn off warnings. The following unchecked conversions are only used
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69 -- internally in this package, and cannot never result in any instances
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70 -- of improperly aliased pointers for the client of the package.
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71
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72 function To_Address is new Unchecked_Conversion (Table_Ptr, Address);
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73 function To_Pointer is new Unchecked_Conversion (Address, Table_Ptr);
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74
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75 pragma Warnings (On);
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76
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77 ------------
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78 -- Append --
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79 ------------
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80
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81 procedure Append (New_Val : Table_Component_Type) is
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82 begin
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83 Set_Item (Table_Index_Type (Last_Val + 1), New_Val);
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84 end Append;
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85
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86 ----------------
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87 -- Append_All --
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88 ----------------
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89
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90 procedure Append_All (New_Vals : Table_Type) is
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91 begin
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92 for J in New_Vals'Range loop
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93 Append (New_Vals (J));
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94 end loop;
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95 end Append_All;
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96
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97 --------------------
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98 -- Decrement_Last --
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99 --------------------
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100
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101 procedure Decrement_Last is
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102 begin
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103 Last_Val := Last_Val - 1;
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104 end Decrement_Last;
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105
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106 ----------
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107 -- Free --
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108 ----------
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109
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110 procedure Free is
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111 begin
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112 Free (To_Address (Table));
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113 Table := null;
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114 Length := 0;
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115 end Free;
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116
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117 --------------------
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118 -- Increment_Last --
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119 --------------------
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120
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121 procedure Increment_Last is
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122 begin
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123 Last_Val := Last_Val + 1;
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124
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125 if Last_Val > Max then
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126 Reallocate;
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127 end if;
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128 end Increment_Last;
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129
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130 ----------
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131 -- Init --
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132 ----------
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133
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134 procedure Init is
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135 Old_Length : constant Int := Length;
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136
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137 begin
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138 Locked := False;
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139 Last_Val := Min - 1;
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140 Max := Min + (Table_Initial * Table_Factor) - 1;
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141 Length := Max - Min + 1;
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142
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143 -- If table is same size as before (happens when table is never
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144 -- expanded which is a common case), then simply reuse it. Note
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145 -- that this also means that an explicit Init call right after
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146 -- the implicit one in the package body is harmless.
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147
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148 if Old_Length = Length then
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149 return;
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150
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151 -- Otherwise we can use Reallocate to get a table of the right size.
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152 -- Note that Reallocate works fine to allocate a table of the right
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153 -- initial size when it is first allocated.
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154
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155 else
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156 Reallocate;
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157 end if;
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158 end Init;
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159
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160 ----------
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161 -- Last --
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162 ----------
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163
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164 function Last return Table_Index_Type is
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165 begin
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166 return Table_Index_Type (Last_Val);
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167 end Last;
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168
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169 ----------------
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170 -- Reallocate --
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171 ----------------
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172
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173 procedure Reallocate is
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174 New_Size : Memory.size_t;
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175 New_Length : Long_Long_Integer;
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176
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177 begin
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178 if Max < Last_Val then
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179 pragma Assert (not Locked);
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180
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181 -- Make sure that we have at least the initial allocation. This
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182 -- is needed in cases where a zero length table is written out.
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183
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184 Length := Int'Max (Length, Table_Initial);
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185
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186 -- Now increment table length until it is sufficiently large. Use
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187 -- the increment value or 10, which ever is larger (the reason
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188 -- for the use of 10 here is to ensure that the table does really
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189 -- increase in size (which would not be the case for a table of
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190 -- length 10 increased by 3% for instance). Do the intermediate
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191 -- calculation in Long_Long_Integer to avoid overflow.
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192
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193 while Max < Last_Val loop
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194 New_Length :=
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195 Long_Long_Integer (Length) *
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196 (100 + Long_Long_Integer (Table_Increment)) / 100;
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197 Length := Int'Max (Int (New_Length), Length + 10);
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198 Max := Min + Length - 1;
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199 end loop;
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200
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201 if Debug_Flag_D then
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202 Write_Str ("--> Allocating new ");
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203 Write_Str (Table_Name);
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204 Write_Str (" table, size = ");
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205 Write_Int (Max - Min + 1);
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206 Write_Eol;
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207 end if;
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208 end if;
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209
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210 -- Do the intermediate calculation in size_t to avoid signed overflow
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211
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212 New_Size :=
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213 Memory.size_t (Max - Min + 1) *
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214 (Table_Type'Component_Size / Storage_Unit);
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215
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216 if Table = null then
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217 Table := To_Pointer (Alloc (New_Size));
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218
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219 elsif New_Size > 0 then
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220 Table :=
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221 To_Pointer (Realloc (Ptr => To_Address (Table),
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222 Size => New_Size));
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223 end if;
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224
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225 if Length /= 0 and then Table = null then
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226 Set_Standard_Error;
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227 Write_Str ("available memory exhausted");
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228 Write_Eol;
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229 Set_Standard_Output;
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230 raise Unrecoverable_Error;
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231 end if;
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232 end Reallocate;
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233
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234 -------------
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235 -- Release --
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236 -------------
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237
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238 procedure Release is
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239 Extra_Length : Int;
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240 Size : Memory.size_t;
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241
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242 begin
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243 Length := Last_Val - Int (Table_Low_Bound) + 1;
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244 Size := Memory.size_t (Length) *
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245 (Table_Type'Component_Size / Storage_Unit);
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246
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247 -- If the size of the table exceeds the release threshold then leave
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248 -- space to store as many extra elements as 0.1% of the table length.
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249
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250 if Release_Threshold > 0
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251 and then Size > Memory.size_t (Release_Threshold)
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252 then
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253 Extra_Length := Length / 1000;
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254 Length := Length + Extra_Length;
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255 Max := Int (Table_Low_Bound) + Length - 1;
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256
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257 if Debug_Flag_D then
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258 Write_Str ("--> Release_Threshold reached (length=");
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259 Write_Int (Int (Size));
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260 Write_Str ("): leaving room space for ");
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261 Write_Int (Extra_Length);
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262 Write_Str (" components");
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263 Write_Eol;
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264 end if;
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265 else
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266 Max := Last_Val;
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267 end if;
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268
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269 Reallocate;
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270 end Release;
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271
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272 -------------
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273 -- Restore --
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274 -------------
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275
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276 procedure Restore (T : Saved_Table) is
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277 begin
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278 Free (To_Address (Table));
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279 Last_Val := T.Last_Val;
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280 Max := T.Max;
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281 Table := T.Table;
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282 Length := Max - Min + 1;
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283 end Restore;
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284
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285 ----------
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286 -- Save --
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287 ----------
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288
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289 function Save return Saved_Table is
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290 Res : Saved_Table;
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291
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292 begin
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293 Res.Last_Val := Last_Val;
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294 Res.Max := Max;
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295 Res.Table := Table;
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296
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297 Table := null;
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298 Length := 0;
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299 Init;
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300 return Res;
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301 end Save;
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302
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303 --------------
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304 -- Set_Item --
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305 --------------
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306
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307 procedure Set_Item
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308 (Index : Table_Index_Type;
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309 Item : Table_Component_Type)
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310 is
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311 -- If Item is a value within the current allocation, and we are going
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312 -- to reallocate, then we must preserve an intermediate copy here
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313 -- before calling Increment_Last. Otherwise, if Table_Component_Type
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314 -- is passed by reference, we are going to end up copying from
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315 -- storage that might have been deallocated from Increment_Last
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316 -- calling Reallocate.
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317
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318 subtype Allocated_Table_T is
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319 Table_Type (Table'First .. Table_Index_Type (Max + 1));
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320 -- A constrained table subtype one element larger than the currently
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321 -- allocated table.
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322
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323 Allocated_Table_Address : constant System.Address :=
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324 Table.all'Address;
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325 -- Used for address clause below (we can't use non-static expression
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326 -- Table.all'Address directly in the clause because some older
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327 -- versions of the compiler do not allow it).
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328
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329 Allocated_Table : Allocated_Table_T;
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330 pragma Import (Ada, Allocated_Table);
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331 pragma Suppress (Range_Check, On => Allocated_Table);
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332 for Allocated_Table'Address use Allocated_Table_Address;
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333 -- Allocated_Table represents the currently allocated array, plus one
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334 -- element (the supplementary element is used to have a convenient
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335 -- way of computing the address just past the end of the current
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336 -- allocation). Range checks are suppressed because this unit
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337 -- uses direct calls to System.Memory for allocation, and this can
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338 -- yield misaligned storage (and we cannot rely on the bootstrap
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339 -- compiler supporting specifically disabling alignment checks, so we
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340 -- need to suppress all range checks). It is safe to suppress this
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341 -- check here because we know that a (possibly misaligned) object
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342 -- of that type does actually exist at that address.
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343 -- ??? We should really improve the allocation circuitry here to
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344 -- guarantee proper alignment.
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345
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346 Need_Realloc : constant Boolean := Int (Index) > Max;
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347 -- True if this operation requires storage reallocation (which may
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348 -- involve moving table contents around).
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349
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350 begin
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351 -- If we're going to reallocate, check whether Item references an
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352 -- element of the currently allocated table.
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353
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354 if Need_Realloc
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355 and then Allocated_Table'Address <= Item'Address
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356 and then Item'Address <
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357 Allocated_Table (Table_Index_Type (Max + 1))'Address
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358 then
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359 -- If so, save a copy on the stack because Increment_Last will
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360 -- reallocate storage and might deallocate the current table.
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361
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362 declare
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363 Item_Copy : constant Table_Component_Type := Item;
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364 begin
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365 Set_Last (Index);
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366 Table (Index) := Item_Copy;
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367 end;
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368
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369 else
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370 -- Here we know that either we won't reallocate (case of Index <
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371 -- Max) or that Item is not in the currently allocated table.
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372
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373 if Int (Index) > Last_Val then
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374 Set_Last (Index);
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375 end if;
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376
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377 Table (Index) := Item;
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378 end if;
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379 end Set_Item;
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380
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381 --------------
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382 -- Set_Last --
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383 --------------
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384
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385 procedure Set_Last (New_Val : Table_Index_Type) is
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386 begin
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387 if Int (New_Val) < Last_Val then
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388 Last_Val := Int (New_Val);
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389
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390 else
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391 Last_Val := Int (New_Val);
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392
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393 if Last_Val > Max then
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394 Reallocate;
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395 end if;
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396 end if;
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397 end Set_Last;
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398
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399 ----------------------------
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400 -- Tree_Get_Table_Address --
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401 ----------------------------
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402
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403 function Tree_Get_Table_Address return Address is
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404 begin
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405 if Length = 0 then
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406 return Null_Address;
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407 else
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408 return Table (First)'Address;
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409 end if;
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410 end Tree_Get_Table_Address;
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411
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412 ---------------
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413 -- Tree_Read --
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414 ---------------
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415
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416 -- Note: we allocate only the space required to accommodate the data
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417 -- actually written, which means that a Tree_Write/Tree_Read sequence
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418 -- does an implicit Release.
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419
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420 procedure Tree_Read is
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421 begin
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422 Tree_Read_Int (Max);
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423 Last_Val := Max;
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424 Length := Max - Min + 1;
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425 Reallocate;
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426
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427 Tree_Read_Data
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428 (Tree_Get_Table_Address,
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429 (Last_Val - Int (First) + 1) *
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430
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431 -- Note the importance of parenthesizing the following division
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432 -- to avoid the possibility of intermediate overflow.
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433
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434 (Table_Type'Component_Size / Storage_Unit));
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435 end Tree_Read;
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436
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437 ----------------
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438 -- Tree_Write --
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439 ----------------
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440
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441 -- Note: we write out only the currently valid data, not the entire
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442 -- contents of the allocated array. See note above on Tree_Read.
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443
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444 procedure Tree_Write is
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445 begin
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446 Tree_Write_Int (Int (Last));
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447 Tree_Write_Data
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448 (Tree_Get_Table_Address,
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449 (Last_Val - Int (First) + 1) *
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450 (Table_Type'Component_Size / Storage_Unit));
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451 end Tree_Write;
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452
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453 begin
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454 Init;
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455 end Table;
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456 end Table;
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