1------------------------------------------------------------------------------ 2-- -- 3-- GNAT LIBRARY COMPONENTS -- 4-- -- 5-- ADA.CONTAINERS.HASH_TABLES.GENERIC_KEYS -- 6-- -- 7-- B o d y -- 8-- -- 9-- Copyright (C) 2004-2015, Free Software Foundation, Inc. -- 10-- -- 11-- GNAT is free software; you can redistribute it and/or modify it under -- 12-- terms of the GNU General Public License as published by the Free Soft- -- 13-- ware Foundation; either version 3, or (at your option) any later ver- -- 14-- sion. GNAT is distributed in the hope that it will be useful, but WITH- -- 15-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY -- 16-- or FITNESS FOR A PARTICULAR PURPOSE. -- 17-- -- 18-- As a special exception under Section 7 of GPL version 3, you are granted -- 19-- additional permissions described in the GCC Runtime Library Exception, -- 20-- version 3.1, as published by the Free Software Foundation. -- 21-- -- 22-- You should have received a copy of the GNU General Public License and -- 23-- a copy of the GCC Runtime Library Exception along with this program; -- 24-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- 25-- <http://www.gnu.org/licenses/>. -- 26-- -- 27-- This unit was originally developed by Matthew J Heaney. -- 28------------------------------------------------------------------------------ 29 30package body Ada.Containers.Hash_Tables.Generic_Keys is 31 32 pragma Warnings (Off, "variable ""Busy*"" is not referenced"); 33 pragma Warnings (Off, "variable ""Lock*"" is not referenced"); 34 -- See comment in Ada.Containers.Helpers 35 36 ----------------------------- 37 -- Checked_Equivalent_Keys -- 38 ----------------------------- 39 40 function Checked_Equivalent_Keys 41 (HT : aliased in out Hash_Table_Type; 42 Key : Key_Type; 43 Node : Node_Access) return Boolean 44 is 45 Lock : With_Lock (HT.TC'Unrestricted_Access); 46 begin 47 return Equivalent_Keys (Key, Node); 48 end Checked_Equivalent_Keys; 49 50 ------------------- 51 -- Checked_Index -- 52 ------------------- 53 54 function Checked_Index 55 (HT : aliased in out Hash_Table_Type; 56 Key : Key_Type) return Hash_Type 57 is 58 Lock : With_Lock (HT.TC'Unrestricted_Access); 59 begin 60 return Hash (Key) mod HT.Buckets'Length; 61 end Checked_Index; 62 63 -------------------------- 64 -- Delete_Key_Sans_Free -- 65 -------------------------- 66 67 procedure Delete_Key_Sans_Free 68 (HT : in out Hash_Table_Type; 69 Key : Key_Type; 70 X : out Node_Access) 71 is 72 Indx : Hash_Type; 73 Prev : Node_Access; 74 75 begin 76 if HT.Length = 0 then 77 X := null; 78 return; 79 end if; 80 81 -- Per AI05-0022, the container implementation is required to detect 82 -- element tampering by a generic actual subprogram. 83 84 TC_Check (HT.TC); 85 86 Indx := Checked_Index (HT, Key); 87 X := HT.Buckets (Indx); 88 89 if X = null then 90 return; 91 end if; 92 93 if Checked_Equivalent_Keys (HT, Key, X) then 94 TC_Check (HT.TC); 95 HT.Buckets (Indx) := Next (X); 96 HT.Length := HT.Length - 1; 97 return; 98 end if; 99 100 loop 101 Prev := X; 102 X := Next (Prev); 103 104 if X = null then 105 return; 106 end if; 107 108 if Checked_Equivalent_Keys (HT, Key, X) then 109 TC_Check (HT.TC); 110 Set_Next (Node => Prev, Next => Next (X)); 111 HT.Length := HT.Length - 1; 112 return; 113 end if; 114 end loop; 115 end Delete_Key_Sans_Free; 116 117 ---------- 118 -- Find -- 119 ---------- 120 121 function Find 122 (HT : aliased in out Hash_Table_Type; 123 Key : Key_Type) return Node_Access 124 is 125 Indx : Hash_Type; 126 Node : Node_Access; 127 128 begin 129 if HT.Length = 0 then 130 return null; 131 end if; 132 133 Indx := Checked_Index (HT, Key); 134 135 Node := HT.Buckets (Indx); 136 while Node /= null loop 137 if Checked_Equivalent_Keys (HT, Key, Node) then 138 return Node; 139 end if; 140 Node := Next (Node); 141 end loop; 142 143 return null; 144 end Find; 145 146 -------------------------------- 147 -- Generic_Conditional_Insert -- 148 -------------------------------- 149 150 procedure Generic_Conditional_Insert 151 (HT : in out Hash_Table_Type; 152 Key : Key_Type; 153 Node : out Node_Access; 154 Inserted : out Boolean) 155 is 156 Indx : Hash_Type; 157 158 begin 159 -- Per AI05-0022, the container implementation is required to detect 160 -- element tampering by a generic actual subprogram. 161 162 TC_Check (HT.TC); 163 164 Indx := Checked_Index (HT, Key); 165 Node := HT.Buckets (Indx); 166 167 if Node = null then 168 if Checks and then HT.Length = Count_Type'Last then 169 raise Constraint_Error; 170 end if; 171 172 Node := New_Node (Next => null); 173 Inserted := True; 174 175 HT.Buckets (Indx) := Node; 176 HT.Length := HT.Length + 1; 177 178 return; 179 end if; 180 181 loop 182 if Checked_Equivalent_Keys (HT, Key, Node) then 183 Inserted := False; 184 return; 185 end if; 186 187 Node := Next (Node); 188 189 exit when Node = null; 190 end loop; 191 192 if Checks and then HT.Length = Count_Type'Last then 193 raise Constraint_Error; 194 end if; 195 196 Node := New_Node (Next => HT.Buckets (Indx)); 197 Inserted := True; 198 199 HT.Buckets (Indx) := Node; 200 HT.Length := HT.Length + 1; 201 end Generic_Conditional_Insert; 202 203 ----------------------------- 204 -- Generic_Replace_Element -- 205 ----------------------------- 206 207 procedure Generic_Replace_Element 208 (HT : in out Hash_Table_Type; 209 Node : Node_Access; 210 Key : Key_Type) 211 is 212 pragma Assert (HT.Length > 0); 213 pragma Assert (Node /= null); 214 215 Old_Indx : Hash_Type; 216 New_Indx : constant Hash_Type := Checked_Index (HT, Key); 217 218 New_Bucket : Node_Access renames HT.Buckets (New_Indx); 219 N, M : Node_Access; 220 221 begin 222 -- Per AI05-0022, the container implementation is required to detect 223 -- element tampering by a generic actual subprogram. 224 225 declare 226 Lock : With_Lock (HT.TC'Unrestricted_Access); 227 begin 228 Old_Indx := Hash (Node) mod HT.Buckets'Length; 229 end; 230 231 if Checked_Equivalent_Keys (HT, Key, Node) then 232 TE_Check (HT.TC); 233 234 -- We can change a node's key to Key (that's what Assign is for), but 235 -- only if Key is not already in the hash table. (In a unique-key 236 -- hash table as this one a key is mapped to exactly one node only.) 237 -- The exception is when Key is mapped to Node, in which case the 238 -- change is allowed. 239 240 Assign (Node, Key); 241 return; 242 end if; 243 244 -- Key is not equivalent to Node, so we now have to determine if it's 245 -- equivalent to some other node in the hash table. This is the case 246 -- irrespective of whether Key is in the same or a different bucket from 247 -- Node. 248 249 N := New_Bucket; 250 while N /= null loop 251 if Checks and then Checked_Equivalent_Keys (HT, Key, N) then 252 pragma Assert (N /= Node); 253 raise Program_Error with 254 "attempt to replace existing element"; 255 end if; 256 257 N := Next (N); 258 end loop; 259 260 -- We have determined that Key is not already in the hash table, so 261 -- the change is tentatively allowed. We now perform the standard 262 -- checks to determine whether the hash table is locked (because you 263 -- cannot change an element while it's in use by Query_Element or 264 -- Update_Element), or if the container is busy (because moving a 265 -- node to a different bucket would interfere with iteration). 266 267 if Old_Indx = New_Indx then 268 -- The node is already in the bucket implied by Key. In this case 269 -- we merely change its value without moving it. 270 271 TE_Check (HT.TC); 272 273 Assign (Node, Key); 274 return; 275 end if; 276 277 -- The node is a bucket different from the bucket implied by Key 278 279 TC_Check (HT.TC); 280 281 -- Do the assignment first, before moving the node, so that if Assign 282 -- propagates an exception, then the hash table will not have been 283 -- modified (except for any possible side-effect Assign had on Node). 284 285 Assign (Node, Key); 286 287 -- Now we can safely remove the node from its current bucket 288 289 N := HT.Buckets (Old_Indx); 290 pragma Assert (N /= null); 291 292 if N = Node then 293 HT.Buckets (Old_Indx) := Next (Node); 294 295 else 296 pragma Assert (HT.Length > 1); 297 298 loop 299 M := Next (N); 300 pragma Assert (M /= null); 301 302 if M = Node then 303 Set_Next (Node => N, Next => Next (Node)); 304 exit; 305 end if; 306 307 N := M; 308 end loop; 309 end if; 310 311 -- Now we link the node into its new bucket (corresponding to Key) 312 313 Set_Next (Node => Node, Next => New_Bucket); 314 New_Bucket := Node; 315 end Generic_Replace_Element; 316 317 ----------- 318 -- Index -- 319 ----------- 320 321 function Index 322 (HT : Hash_Table_Type; 323 Key : Key_Type) return Hash_Type 324 is 325 begin 326 return Hash (Key) mod HT.Buckets'Length; 327 end Index; 328 329end Ada.Containers.Hash_Tables.Generic_Keys; 330