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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT COMPILER COMPONENTS --
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4 -- --
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5 -- S Y S T E M . E X C E P T I O N _ 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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145
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9 -- Copyright (C) 1996-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 pragma Compiler_Unit_Warning;
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33
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34 with System.Soft_Links; use System.Soft_Links;
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35
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36 package body System.Exception_Table is
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37
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38 use System.Standard_Library;
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39
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40 type Hash_Val is mod 2 ** 8;
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41 subtype Hash_Idx is Hash_Val range 1 .. 37;
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42
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43 HTable : array (Hash_Idx) of aliased Exception_Data_Ptr;
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44 -- Actual hash table containing all registered exceptions
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45 --
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46 -- The table is very small and the hash function weak, as looking up
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47 -- registered exceptions is rare and minimizing space and time overhead
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48 -- of registration is more important. In addition, it is expected that the
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49 -- exceptions that need to be looked up are registered dynamically, and
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50 -- therefore will be at the begin of the hash chains.
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51 --
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52 -- The table differs from System.HTable.Static_HTable in that the final
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53 -- element of each chain is not marked by null, but by a pointer to self.
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54 -- This way it is possible to defend against the same entry being inserted
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55 -- twice, without having to do a lookup which is relatively expensive for
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56 -- programs with large number
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57 --
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58 -- All non-local subprograms use the global Task_Lock to protect against
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59 -- concurrent use of the exception table. This is needed as local
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60 -- exceptions may be declared concurrently with those declared at the
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61 -- library level.
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62
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63 -- Local Subprograms
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64
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65 generic
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66 with procedure Process (T : Exception_Data_Ptr; More : out Boolean);
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67 procedure Iterate;
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68 -- Iterate over all
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69
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70 function Lookup (Name : String) return Exception_Data_Ptr;
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71 -- Find and return the Exception_Data of the exception with the given Name
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72 -- (which must be in all uppercase), or null if none was registered.
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73
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74 procedure Register (Item : Exception_Data_Ptr);
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75 -- Register an exception with the given Exception_Data in the table.
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76
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77 function Has_Name (Item : Exception_Data_Ptr; Name : String) return Boolean;
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78 -- Return True iff Item.Full_Name and Name are equal. Both names are
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79 -- assumed to be in all uppercase and end with ASCII.NUL.
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80
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81 function Hash (S : String) return Hash_Idx;
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82 -- Return the index in the hash table for S, which is assumed to be all
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83 -- uppercase and end with ASCII.NUL.
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84
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85 --------------
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86 -- Has_Name --
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87 --------------
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88
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89 function Has_Name (Item : Exception_Data_Ptr; Name : String) return Boolean
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90 is
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91 S : constant Big_String_Ptr := To_Ptr (Item.Full_Name);
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92 J : Integer := S'First;
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93
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94 begin
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95 for K in Name'Range loop
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96
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97 -- Note that as both items are terminated with ASCII.NUL, the
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98 -- comparison below must fail for strings of different lengths.
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99
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100 if S (J) /= Name (K) then
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101 return False;
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102 end if;
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103
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104 J := J + 1;
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105 end loop;
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106
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107 return True;
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108 end Has_Name;
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109
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110 ------------
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111 -- Lookup --
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112 ------------
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113
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114 function Lookup (Name : String) return Exception_Data_Ptr is
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115 Prev : Exception_Data_Ptr;
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116 Curr : Exception_Data_Ptr;
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117
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118 begin
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119 Curr := HTable (Hash (Name));
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120 Prev := null;
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121 while Curr /= Prev loop
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122 if Has_Name (Curr, Name) then
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123 return Curr;
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124 end if;
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125
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126 Prev := Curr;
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127 Curr := Curr.HTable_Ptr;
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128 end loop;
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129
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130 return null;
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131 end Lookup;
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132
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133 ----------
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134 -- Hash --
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135 ----------
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136
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137 function Hash (S : String) return Hash_Idx is
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138 Hash : Hash_Val := 0;
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139
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140 begin
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141 for J in S'Range loop
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142 exit when S (J) = ASCII.NUL;
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143 Hash := Hash xor Character'Pos (S (J));
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144 end loop;
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145
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146 return Hash_Idx'First + Hash mod (Hash_Idx'Last - Hash_Idx'First + 1);
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147 end Hash;
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148
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149 -------------
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150 -- Iterate --
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151 -------------
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152
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153 procedure Iterate is
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154 More : Boolean;
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155 Prev, Curr : Exception_Data_Ptr;
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156
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157 begin
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158 Outer : for Idx in HTable'Range loop
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159 Prev := null;
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160 Curr := HTable (Idx);
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161
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162 while Curr /= Prev loop
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163 Process (Curr, More);
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164
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165 exit Outer when not More;
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166
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167 Prev := Curr;
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168 Curr := Curr.HTable_Ptr;
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169 end loop;
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170 end loop Outer;
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171 end Iterate;
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172
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173 --------------
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174 -- Register --
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175 --------------
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176
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177 procedure Register (Item : Exception_Data_Ptr) is
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178 begin
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179 if Item.HTable_Ptr = null then
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180 Prepend_To_Chain : declare
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181 Chain : Exception_Data_Ptr
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182 renames HTable (Hash (To_Ptr (Item.Full_Name).all));
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183
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184 begin
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185 if Chain = null then
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186 Item.HTable_Ptr := Item;
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187 else
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188 Item.HTable_Ptr := Chain;
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189 end if;
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190
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191 Chain := Item;
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192 end Prepend_To_Chain;
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193 end if;
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194 end Register;
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195
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196 -------------------------------
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197 -- Get_Registered_Exceptions --
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198 -------------------------------
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199
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200 procedure Get_Registered_Exceptions
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201 (List : out Exception_Data_Array;
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202 Last : out Integer)
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203 is
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204 procedure Get_One (Item : Exception_Data_Ptr; More : out Boolean);
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205 -- Add Item to List (List'First .. Last) by first incrementing Last
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206 -- and storing Item in List (Last). Last should be in List'First - 1
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207 -- and List'Last.
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208
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209 procedure Get_All is new Iterate (Get_One);
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210 -- Store all registered exceptions in List, updating Last
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211
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212 -------------
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213 -- Get_One --
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214 -------------
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215
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216 procedure Get_One (Item : Exception_Data_Ptr; More : out Boolean) is
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217 begin
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218 if Last < List'Last then
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219 Last := Last + 1;
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220 List (Last) := Item;
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221 More := True;
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222
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223 else
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224 More := False;
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225 end if;
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226 end Get_One;
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227
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228 begin
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229 -- In this routine the invariant is that List (List'First .. Last)
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230 -- contains the registered exceptions retrieved so far.
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231
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232 Last := List'First - 1;
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233
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234 Lock_Task.all;
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235 Get_All;
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236 Unlock_Task.all;
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237 end Get_Registered_Exceptions;
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238
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239 ------------------------
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240 -- Internal_Exception --
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241 ------------------------
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242
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243 function Internal_Exception
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244 (X : String;
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245 Create_If_Not_Exist : Boolean := True) return Exception_Data_Ptr
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246 is
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247 -- If X was not yet registered and Create_if_Not_Exist is True,
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248 -- dynamically allocate and register a new exception.
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249
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250 type String_Ptr is access all String;
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251
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252 Dyn_Copy : String_Ptr;
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253 Copy : aliased String (X'First .. X'Last + 1);
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254 Result : Exception_Data_Ptr;
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255
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256 begin
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257 Lock_Task.all;
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258
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259 Copy (X'Range) := X;
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260 Copy (Copy'Last) := ASCII.NUL;
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261 Result := Lookup (Copy);
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262
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263 -- If unknown exception, create it on the heap. This is a legitimate
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264 -- situation in the distributed case when an exception is defined
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265 -- only in a partition
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266
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267 if Result = null and then Create_If_Not_Exist then
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268 Dyn_Copy := new String'(Copy);
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269
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270 Result :=
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271 new Exception_Data'
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272 (Not_Handled_By_Others => False,
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273 Lang => 'A',
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274 Name_Length => Copy'Length,
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275 Full_Name => Dyn_Copy.all'Address,
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276 HTable_Ptr => null,
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277 Foreign_Data => Null_Address,
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278 Raise_Hook => null);
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279
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280 Register (Result);
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281 end if;
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282
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283 Unlock_Task.all;
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284
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285 return Result;
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286 end Internal_Exception;
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287
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288 ------------------------
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289 -- Register_Exception --
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290 ------------------------
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291
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292 procedure Register_Exception (X : Exception_Data_Ptr) is
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293 begin
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294 Lock_Task.all;
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295 Register (X);
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296 Unlock_Task.all;
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297 end Register_Exception;
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298
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299 ---------------------------------
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300 -- Registered_Exceptions_Count --
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301 ---------------------------------
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302
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303 function Registered_Exceptions_Count return Natural is
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304 Count : Natural := 0;
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305
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306 procedure Count_Item (Item : Exception_Data_Ptr; More : out Boolean);
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307 -- Update Count for given Item
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308
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309 procedure Count_Item (Item : Exception_Data_Ptr; More : out Boolean) is
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310 pragma Unreferenced (Item);
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311 begin
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312 Count := Count + 1;
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313 More := Count < Natural'Last;
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314 end Count_Item;
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315
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316 procedure Count_All is new Iterate (Count_Item);
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317
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318 begin
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319 Lock_Task.all;
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320 Count_All;
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321 Unlock_Task.all;
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322
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323 return Count;
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324 end Registered_Exceptions_Count;
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325
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326 begin
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327 -- Register the standard exceptions at elaboration time
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328
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329 -- We don't need to use the locking version here as the elaboration
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330 -- will not be concurrent and no tasks can call any subprograms of this
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331 -- unit before it has been elaborated.
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332
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333 Register (Abort_Signal_Def'Access);
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334 Register (Tasking_Error_Def'Access);
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335 Register (Storage_Error_Def'Access);
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336 Register (Program_Error_Def'Access);
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337 Register (Numeric_Error_Def'Access);
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338 Register (Constraint_Error_Def'Access);
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339 end System.Exception_Table;
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