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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- S Y S T E M . P O O L _ S I Z E --
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6 -- --
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7 -- B o d y --
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8 -- --
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9 -- Copyright (C) 1992-2019, Free Software Foundation, Inc. --
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111
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10 -- --
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11 -- GNAT is free software; you can redistribute it and/or modify it under --
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12 -- terms of the GNU General Public License as published by the Free Soft- --
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13 -- ware Foundation; either version 3, or (at your option) any later ver- --
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14 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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15 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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16 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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17 -- --
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18 -- As a special exception under Section 7 of GPL version 3, you are granted --
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19 -- additional permissions described in the GCC Runtime Library Exception, --
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20 -- version 3.1, as published by the Free Software Foundation. --
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21 -- --
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22 -- You should have received a copy of the GNU General Public License and --
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23 -- a copy of the GCC Runtime Library Exception along with this program; --
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24 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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25 -- <http://www.gnu.org/licenses/>. --
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26 -- --
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27 -- GNAT was originally developed by the GNAT team at New York University. --
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28 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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29 -- --
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30 ------------------------------------------------------------------------------
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31
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32 with System.Soft_Links;
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33
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34 with Ada.Unchecked_Conversion;
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35
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36 package body System.Pool_Size is
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37
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38 package SSE renames System.Storage_Elements;
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39 use type SSE.Storage_Offset;
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40
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41 -- Even though these storage pools are typically only used by a single
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42 -- task, if multiple tasks are declared at the same or a more nested scope
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43 -- as the storage pool, there still may be concurrent access. The current
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44 -- implementation of Stack_Bounded_Pool always uses a global lock for
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45 -- protecting access. This should eventually be replaced by an atomic
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46 -- linked list implementation for efficiency reasons.
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47
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48 package SSL renames System.Soft_Links;
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49
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50 type Storage_Count_Access is access SSE.Storage_Count;
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51 function To_Storage_Count_Access is
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52 new Ada.Unchecked_Conversion (Address, Storage_Count_Access);
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53
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54 SC_Size : constant := SSE.Storage_Count'Object_Size / System.Storage_Unit;
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55
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56 package Variable_Size_Management is
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57
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58 -- Embedded pool that manages allocation of variable-size data
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59
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60 -- This pool is used as soon as the Elmt_Size of the pool object is 0
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61
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62 -- Allocation is done on the first chunk long enough for the request.
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63 -- Deallocation just puts the freed chunk at the beginning of the list.
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64
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65 procedure Initialize (Pool : in out Stack_Bounded_Pool);
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66 procedure Allocate
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67 (Pool : in out Stack_Bounded_Pool;
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68 Address : out System.Address;
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69 Storage_Size : SSE.Storage_Count;
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70 Alignment : SSE.Storage_Count);
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71
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72 procedure Deallocate
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73 (Pool : in out Stack_Bounded_Pool;
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74 Address : System.Address;
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75 Storage_Size : SSE.Storage_Count;
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76 Alignment : SSE.Storage_Count);
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77 end Variable_Size_Management;
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78
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79 package Vsize renames Variable_Size_Management;
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80
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81 --------------
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82 -- Allocate --
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83 --------------
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84
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85 procedure Allocate
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86 (Pool : in out Stack_Bounded_Pool;
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87 Address : out System.Address;
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88 Storage_Size : SSE.Storage_Count;
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89 Alignment : SSE.Storage_Count)
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90 is
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91 begin
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92 SSL.Lock_Task.all;
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93
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94 if Pool.Elmt_Size = 0 then
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95 Vsize.Allocate (Pool, Address, Storage_Size, Alignment);
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96
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97 elsif Pool.First_Free /= 0 then
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98 Address := Pool.The_Pool (Pool.First_Free)'Address;
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99 Pool.First_Free := To_Storage_Count_Access (Address).all;
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100
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101 elsif
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102 Pool.First_Empty <= (Pool.Pool_Size - Pool.Aligned_Elmt_Size + 1)
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103 then
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104 Address := Pool.The_Pool (Pool.First_Empty)'Address;
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105 Pool.First_Empty := Pool.First_Empty + Pool.Aligned_Elmt_Size;
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106
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107 else
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108 raise Storage_Error;
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109 end if;
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110
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111 SSL.Unlock_Task.all;
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112
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113 exception
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114 when others =>
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115 SSL.Unlock_Task.all;
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116 raise;
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117 end Allocate;
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118
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119 ----------------
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120 -- Deallocate --
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121 ----------------
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122
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123 procedure Deallocate
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124 (Pool : in out Stack_Bounded_Pool;
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125 Address : System.Address;
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126 Storage_Size : SSE.Storage_Count;
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127 Alignment : SSE.Storage_Count)
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128 is
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129 begin
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130 SSL.Lock_Task.all;
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131
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132 if Pool.Elmt_Size = 0 then
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133 Vsize.Deallocate (Pool, Address, Storage_Size, Alignment);
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134
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135 else
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136 To_Storage_Count_Access (Address).all := Pool.First_Free;
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137 Pool.First_Free := Address - Pool.The_Pool'Address + 1;
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138 end if;
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139
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140 SSL.Unlock_Task.all;
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141 exception
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142 when others =>
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143 SSL.Unlock_Task.all;
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144 raise;
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145 end Deallocate;
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146
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147 ----------------
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148 -- Initialize --
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149 ----------------
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150
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151 procedure Initialize (Pool : in out Stack_Bounded_Pool) is
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152
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153 -- Define the appropriate alignment for allocations. This is the
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154 -- maximum of the requested alignment, and the alignment required
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155 -- for Storage_Count values. The latter test is to ensure that we
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156 -- can properly reference the linked list pointers for free lists.
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157
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158 Align : constant SSE.Storage_Count :=
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159 SSE.Storage_Count'Max
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160 (SSE.Storage_Count'Alignment, Pool.Alignment);
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161
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162 begin
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163 if Pool.Elmt_Size = 0 then
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164 Vsize.Initialize (Pool);
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165
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166 else
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167 Pool.First_Free := 0;
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168 Pool.First_Empty := 1;
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169
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170 -- Compute the size to allocate given the size of the element and
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171 -- the possible alignment requirement as defined above.
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172
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173 Pool.Aligned_Elmt_Size :=
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174 SSE.Storage_Count'Max (SC_Size,
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175 ((Pool.Elmt_Size + Align - 1) / Align) * Align);
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176 end if;
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177 end Initialize;
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178
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179 ------------------
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180 -- Storage_Size --
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181 ------------------
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182
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183 function Storage_Size
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184 (Pool : Stack_Bounded_Pool) return SSE.Storage_Count
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185 is
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186 begin
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187 return Pool.Pool_Size;
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188 end Storage_Size;
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189
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190 ------------------------------
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191 -- Variable_Size_Management --
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192 ------------------------------
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193
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194 package body Variable_Size_Management is
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195
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196 Minimum_Size : constant := 2 * SC_Size;
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197
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198 procedure Set_Size
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199 (Pool : Stack_Bounded_Pool;
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200 Chunk, Size : SSE.Storage_Count);
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201 -- Update the field 'size' of a chunk of available storage
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202
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203 procedure Set_Next
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204 (Pool : Stack_Bounded_Pool;
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205 Chunk, Next : SSE.Storage_Count);
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206 -- Update the field 'next' of a chunk of available storage
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207
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208 function Size
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209 (Pool : Stack_Bounded_Pool;
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210 Chunk : SSE.Storage_Count) return SSE.Storage_Count;
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211 -- Fetch the field 'size' of a chunk of available storage
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212
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213 function Next
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214 (Pool : Stack_Bounded_Pool;
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215 Chunk : SSE.Storage_Count) return SSE.Storage_Count;
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216 -- Fetch the field 'next' of a chunk of available storage
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217
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218 function Chunk_Of
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219 (Pool : Stack_Bounded_Pool;
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220 Addr : System.Address) return SSE.Storage_Count;
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221 -- Give the chunk number in the pool from its Address
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222
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223 --------------
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224 -- Allocate --
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225 --------------
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226
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227 procedure Allocate
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228 (Pool : in out Stack_Bounded_Pool;
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229 Address : out System.Address;
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230 Storage_Size : SSE.Storage_Count;
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231 Alignment : SSE.Storage_Count)
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232 is
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233 Chunk : SSE.Storage_Count;
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234 New_Chunk : SSE.Storage_Count;
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235 Prev_Chunk : SSE.Storage_Count;
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236 Our_Align : constant SSE.Storage_Count :=
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237 SSE.Storage_Count'Max (SSE.Storage_Count'Alignment,
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238 Alignment);
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239 Align_Size : constant SSE.Storage_Count :=
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240 SSE.Storage_Count'Max (
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241 Minimum_Size,
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242 ((Storage_Size + Our_Align - 1) / Our_Align) *
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243 Our_Align);
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244
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245 begin
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246 -- Look for the first big enough chunk
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247
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248 Prev_Chunk := Pool.First_Free;
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249 Chunk := Next (Pool, Prev_Chunk);
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250
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251 while Chunk /= 0 and then Size (Pool, Chunk) < Align_Size loop
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252 Prev_Chunk := Chunk;
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253 Chunk := Next (Pool, Chunk);
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254 end loop;
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255
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256 -- Raise storage_error if no big enough chunk available
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257
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258 if Chunk = 0 then
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259 raise Storage_Error;
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260 end if;
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261
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262 -- When the chunk is bigger than what is needed, take appropriate
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263 -- amount and build a new shrinked chunk with the remainder.
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264
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265 if Size (Pool, Chunk) - Align_Size > Minimum_Size then
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266 New_Chunk := Chunk + Align_Size;
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267 Set_Size (Pool, New_Chunk, Size (Pool, Chunk) - Align_Size);
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268 Set_Next (Pool, New_Chunk, Next (Pool, Chunk));
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269 Set_Next (Pool, Prev_Chunk, New_Chunk);
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270
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271 -- If the chunk is the right size, just delete it from the chain
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272
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273 else
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274 Set_Next (Pool, Prev_Chunk, Next (Pool, Chunk));
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275 end if;
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276
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277 Address := Pool.The_Pool (Chunk)'Address;
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278 end Allocate;
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279
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280 --------------
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281 -- Chunk_Of --
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282 --------------
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283
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284 function Chunk_Of
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285 (Pool : Stack_Bounded_Pool;
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286 Addr : System.Address) return SSE.Storage_Count
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287 is
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288 begin
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289 return 1 + abs (Addr - Pool.The_Pool (1)'Address);
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290 end Chunk_Of;
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291
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292 ----------------
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293 -- Deallocate --
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294 ----------------
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295
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296 procedure Deallocate
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297 (Pool : in out Stack_Bounded_Pool;
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298 Address : System.Address;
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299 Storage_Size : SSE.Storage_Count;
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300 Alignment : SSE.Storage_Count)
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301 is
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302 pragma Warnings (Off, Pool);
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303
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304 Align_Size : constant SSE.Storage_Count :=
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305 ((Storage_Size + Alignment - 1) / Alignment) *
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306 Alignment;
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307 Chunk : constant SSE.Storage_Count := Chunk_Of (Pool, Address);
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308
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309 begin
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310 -- Attach the freed chunk to the chain
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311
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312 Set_Size (Pool, Chunk,
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313 SSE.Storage_Count'Max (Align_Size, Minimum_Size));
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314 Set_Next (Pool, Chunk, Next (Pool, Pool.First_Free));
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315 Set_Next (Pool, Pool.First_Free, Chunk);
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316
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317 end Deallocate;
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318
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319 ----------------
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320 -- Initialize --
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321 ----------------
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322
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323 procedure Initialize (Pool : in out Stack_Bounded_Pool) is
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324 begin
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325 Pool.First_Free := 1;
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326
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327 if Pool.Pool_Size > Minimum_Size then
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328 Set_Next (Pool, Pool.First_Free, Pool.First_Free + Minimum_Size);
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329 Set_Size (Pool, Pool.First_Free, 0);
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330 Set_Size (Pool, Pool.First_Free + Minimum_Size,
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331 Pool.Pool_Size - Minimum_Size);
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332 Set_Next (Pool, Pool.First_Free + Minimum_Size, 0);
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333 end if;
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334 end Initialize;
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335
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336 ----------
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337 -- Next --
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338 ----------
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339
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340 function Next
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341 (Pool : Stack_Bounded_Pool;
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342 Chunk : SSE.Storage_Count) return SSE.Storage_Count
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343 is
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344 begin
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345 pragma Warnings (Off);
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346 -- Kill alignment warnings, we are careful to make sure
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347 -- that the alignment is correct.
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348
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349 return To_Storage_Count_Access
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350 (Pool.The_Pool (Chunk + SC_Size)'Address).all;
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351
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352 pragma Warnings (On);
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353 end Next;
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354
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355 --------------
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356 -- Set_Next --
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357 --------------
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358
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359 procedure Set_Next
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360 (Pool : Stack_Bounded_Pool;
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361 Chunk, Next : SSE.Storage_Count)
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362 is
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363 begin
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364 pragma Warnings (Off);
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365 -- Kill alignment warnings, we are careful to make sure
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366 -- that the alignment is correct.
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367
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368 To_Storage_Count_Access
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369 (Pool.The_Pool (Chunk + SC_Size)'Address).all := Next;
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370
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371 pragma Warnings (On);
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372 end Set_Next;
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373
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374 --------------
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375 -- Set_Size --
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376 --------------
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377
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378 procedure Set_Size
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379 (Pool : Stack_Bounded_Pool;
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380 Chunk, Size : SSE.Storage_Count)
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381 is
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382 begin
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383 pragma Warnings (Off);
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384 -- Kill alignment warnings, we are careful to make sure
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385 -- that the alignment is correct.
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386
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387 To_Storage_Count_Access
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388 (Pool.The_Pool (Chunk)'Address).all := Size;
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389
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390 pragma Warnings (On);
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391 end Set_Size;
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392
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393 ----------
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394 -- Size --
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395 ----------
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396
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397 function Size
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398 (Pool : Stack_Bounded_Pool;
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399 Chunk : SSE.Storage_Count) return SSE.Storage_Count
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400 is
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401 begin
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402 pragma Warnings (Off);
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403 -- Kill alignment warnings, we are careful to make sure
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404 -- that the alignment is correct.
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405
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406 return To_Storage_Count_Access (Pool.The_Pool (Chunk)'Address).all;
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407
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408 pragma Warnings (On);
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409 end Size;
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410
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411 end Variable_Size_Management;
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412 end System.Pool_Size;
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