1 ------------------------------------------------------------------------------
3 -- GNAT LIBRARY COMPONENTS --
5 -- ADA.CONTAINERS.RED_BLACK_TREES.GENERIC_BOUNDED_KEYS --
9 -- Copyright (C) 2004-2011, Free Software Foundation, Inc. --
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. --
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. --
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/>. --
27 -- This unit was originally developed by Matthew J Heaney. --
28 ------------------------------------------------------------------------------
30 package body Ada.Containers.Red_Black_Trees.Generic_Bounded_Keys is
32 package Ops renames Tree_Operations;
41 (Tree : Tree_Type'Class;
42 Key : Key_Type) return Count_Type
46 N : Nodes_Type renames Tree.Nodes;
53 if Is_Greater_Key_Node (Key, N (X)) then
54 X := Ops.Right (N (X));
57 X := Ops.Left (N (X));
69 (Tree : Tree_Type'Class;
70 Key : Key_Type) return Count_Type
74 N : Nodes_Type renames Tree.Nodes;
81 if Is_Greater_Key_Node (Key, N (X)) then
82 X := Ops.Right (N (X));
85 X := Ops.Left (N (X));
93 if Is_Less_Key_Node (Key, N (Y)) then
105 (Tree : Tree_Type'Class;
106 Key : Key_Type) return Count_Type
110 N : Nodes_Type renames Tree.Nodes;
117 if Is_Less_Key_Node (Key, N (X)) then
118 X := Ops.Left (N (X));
121 X := Ops.Right (N (X));
128 --------------------------------
129 -- Generic_Conditional_Insert --
130 --------------------------------
132 procedure Generic_Conditional_Insert
133 (Tree : in out Tree_Type'Class;
135 Node : out Count_Type;
136 Inserted : out Boolean)
140 N : Nodes_Type renames Tree.Nodes;
143 -- This is a "conditional" insertion, meaning that the insertion request
144 -- can "fail" in the sense that no new node is created. If the Key is
145 -- equivalent to an existing node, then we return the existing node and
146 -- Inserted is set to False. Otherwise, we allocate a new node (via
147 -- Insert_Post) and Inserted is set to True.
149 -- Note that we are testing for equivalence here, not equality. Key must
150 -- be strictly less than its next neighbor, and strictly greater than
151 -- its previous neighbor, in order for the conditional insertion to
154 -- We search the tree to find the nearest neighbor of Key, which is
155 -- either the smallest node greater than Key (Inserted is True), or the
156 -- largest node less or equivalent to Key (Inserted is False).
163 Inserted := Is_Less_Key_Node (Key, N (X));
164 X := (if Inserted then Ops.Left (N (X)) else Ops.Right (N (X)));
169 -- Either Tree is empty, or Key is less than Y. If Y is the first
170 -- node in the tree, then there are no other nodes that we need to
171 -- search for, and we insert a new node into the tree.
173 if Y = Tree.First then
174 Insert_Post (Tree, Y, True, Node);
178 -- Y is the next nearest-neighbor of Key. We know that Key is not
179 -- equivalent to Y (because Key is strictly less than Y), so we move
180 -- to the previous node, the nearest-neighbor just smaller or
181 -- equivalent to Key.
183 Node := Ops.Previous (Tree, Y);
186 -- Y is the previous nearest-neighbor of Key. We know that Key is not
187 -- less than Y, which means either that Key is equivalent to Y, or
193 -- Key is equivalent to or greater than Node. We must resolve which is
194 -- the case, to determine whether the conditional insertion succeeds.
196 if Is_Greater_Key_Node (Key, N (Node)) then
198 -- Key is strictly greater than Node, which means that Key is not
199 -- equivalent to Node. In this case, the insertion succeeds, and we
200 -- insert a new node into the tree.
202 Insert_Post (Tree, Y, Inserted, Node);
207 -- Key is equivalent to Node. This is a conditional insertion, so we do
208 -- not insert a new node in this case. We return the existing node and
209 -- report that no insertion has occurred.
212 end Generic_Conditional_Insert;
214 ------------------------------------------
215 -- Generic_Conditional_Insert_With_Hint --
216 ------------------------------------------
218 procedure Generic_Conditional_Insert_With_Hint
219 (Tree : in out Tree_Type'Class;
220 Position : Count_Type;
222 Node : out Count_Type;
223 Inserted : out Boolean)
225 N : Nodes_Type renames Tree.Nodes;
228 -- The purpose of a hint is to avoid a search from the root of
229 -- tree. If we have it hint it means we only need to traverse the
230 -- subtree rooted at the hint to find the nearest neighbor. Note
231 -- that finding the neighbor means merely walking the tree; this
232 -- is not a search and the only comparisons that occur are with
233 -- the hint and its neighbor.
235 -- If Position is 0, this is interpreted to mean that Key is
236 -- large relative to the nodes in the tree. If the tree is empty,
237 -- or Key is greater than the last node in the tree, then we're
238 -- done; otherwise the hint was "wrong" and we must search.
240 if Position = 0 then -- largest
242 or else Is_Greater_Key_Node (Key, N (Tree.Last))
244 Insert_Post (Tree, Tree.Last, False, Node);
247 Conditional_Insert_Sans_Hint (Tree, Key, Node, Inserted);
253 pragma Assert (Tree.Length > 0);
255 -- A hint can either name the node that immediately follows Key,
256 -- or immediately precedes Key. We first test whether Key is
257 -- less than the hint, and if so we compare Key to the node that
258 -- precedes the hint. If Key is both less than the hint and
259 -- greater than the hint's preceding neighbor, then we're done;
260 -- otherwise we must search.
262 -- Note also that a hint can either be an anterior node or a leaf
263 -- node. A new node is always inserted at the bottom of the tree
264 -- (at least prior to rebalancing), becoming the new left or
265 -- right child of leaf node (which prior to the insertion must
266 -- necessarily be null, since this is a leaf). If the hint names
267 -- an anterior node then its neighbor must be a leaf, and so
268 -- (here) we insert after the neighbor. If the hint names a leaf
269 -- then its neighbor must be anterior and so we insert before the
272 if Is_Less_Key_Node (Key, N (Position)) then
274 Before : constant Count_Type := Ops.Previous (Tree, Position);
278 Insert_Post (Tree, Tree.First, True, Node);
281 elsif Is_Greater_Key_Node (Key, N (Before)) then
282 if Ops.Right (N (Before)) = 0 then
283 Insert_Post (Tree, Before, False, Node);
285 Insert_Post (Tree, Position, True, Node);
291 Conditional_Insert_Sans_Hint (Tree, Key, Node, Inserted);
298 -- We know that Key isn't less than the hint so we try again,
299 -- this time to see if it's greater than the hint. If so we
300 -- compare Key to the node that follows the hint. If Key is both
301 -- greater than the hint and less than the hint's next neighbor,
302 -- then we're done; otherwise we must search.
304 if Is_Greater_Key_Node (Key, N (Position)) then
306 After : constant Count_Type := Ops.Next (Tree, Position);
310 Insert_Post (Tree, Tree.Last, False, Node);
313 elsif Is_Less_Key_Node (Key, N (After)) then
314 if Ops.Right (N (Position)) = 0 then
315 Insert_Post (Tree, Position, False, Node);
317 Insert_Post (Tree, After, True, Node);
323 Conditional_Insert_Sans_Hint (Tree, Key, Node, Inserted);
330 -- We know that Key is neither less than the hint nor greater
331 -- than the hint, and that's the definition of equivalence.
332 -- There's nothing else we need to do, since a search would just
333 -- reach the same conclusion.
337 end Generic_Conditional_Insert_With_Hint;
339 -------------------------
340 -- Generic_Insert_Post --
341 -------------------------
343 procedure Generic_Insert_Post
344 (Tree : in out Tree_Type'Class;
349 N : Nodes_Type renames Tree.Nodes;
352 if Tree.Length >= Tree.Capacity then
353 raise Capacity_Error with "not enough capacity to insert new item";
356 if Tree.Busy > 0 then
357 raise Program_Error with
358 "attempt to tamper with cursors (container is busy)";
362 pragma Assert (Z /= 0);
365 pragma Assert (Tree.Length = 0);
366 pragma Assert (Tree.Root = 0);
367 pragma Assert (Tree.First = 0);
368 pragma Assert (Tree.Last = 0);
375 pragma Assert (Ops.Left (N (Y)) = 0);
377 Ops.Set_Left (N (Y), Z);
379 if Y = Tree.First then
384 pragma Assert (Ops.Right (N (Y)) = 0);
386 Ops.Set_Right (N (Y), Z);
388 if Y = Tree.Last then
393 Ops.Set_Color (N (Z), Red);
394 Ops.Set_Parent (N (Z), Y);
395 Ops.Rebalance_For_Insert (Tree, Z);
396 Tree.Length := Tree.Length + 1;
397 end Generic_Insert_Post;
399 -----------------------
400 -- Generic_Iteration --
401 -----------------------
403 procedure Generic_Iteration
404 (Tree : Tree_Type'Class;
407 procedure Iterate (Index : Count_Type);
413 procedure Iterate (Index : Count_Type) is
415 N : Nodes_Type renames Tree.Nodes;
420 if Is_Less_Key_Node (Key, N (J)) then
421 J := Ops.Left (N (J));
422 elsif Is_Greater_Key_Node (Key, N (J)) then
423 J := Ops.Right (N (J));
425 Iterate (Ops.Left (N (J)));
427 J := Ops.Right (N (J));
432 -- Start of processing for Generic_Iteration
436 end Generic_Iteration;
438 -------------------------------
439 -- Generic_Reverse_Iteration --
440 -------------------------------
442 procedure Generic_Reverse_Iteration
443 (Tree : Tree_Type'Class;
446 procedure Iterate (Index : Count_Type);
452 procedure Iterate (Index : Count_Type) is
454 N : Nodes_Type renames Tree.Nodes;
459 if Is_Less_Key_Node (Key, N (J)) then
460 J := Ops.Left (N (J));
461 elsif Is_Greater_Key_Node (Key, N (J)) then
462 J := Ops.Right (N (J));
464 Iterate (Ops.Right (N (J)));
466 J := Ops.Left (N (J));
471 -- Start of processing for Generic_Reverse_Iteration
475 end Generic_Reverse_Iteration;
477 ----------------------------------
478 -- Generic_Unconditional_Insert --
479 ----------------------------------
481 procedure Generic_Unconditional_Insert
482 (Tree : in out Tree_Type'Class;
484 Node : out Count_Type)
488 N : Nodes_Type renames Tree.Nodes;
499 Before := Is_Less_Key_Node (Key, N (X));
500 X := (if Before then Ops.Left (N (X)) else Ops.Right (N (X)));
503 Insert_Post (Tree, Y, Before, Node);
504 end Generic_Unconditional_Insert;
506 --------------------------------------------
507 -- Generic_Unconditional_Insert_With_Hint --
508 --------------------------------------------
510 procedure Generic_Unconditional_Insert_With_Hint
511 (Tree : in out Tree_Type'Class;
514 Node : out Count_Type)
516 N : Nodes_Type renames Tree.Nodes;
519 -- There are fewer constraints for an unconditional insertion
520 -- than for a conditional insertion, since we allow duplicate
521 -- keys. So instead of having to check (say) whether Key is
522 -- (strictly) greater than the hint's previous neighbor, here we
523 -- allow Key to be equal to or greater than the previous node.
525 -- There is the issue of what to do if Key is equivalent to the
526 -- hint. Does the new node get inserted before or after the hint?
527 -- We decide that it gets inserted after the hint, reasoning that
528 -- this is consistent with behavior for non-hint insertion, which
529 -- inserts a new node after existing nodes with equivalent keys.
531 -- First we check whether the hint is null, which is interpreted
532 -- to mean that Key is large relative to existing nodes.
533 -- Following our rule above, if Key is equal to or greater than
534 -- the last node, then we insert the new node immediately after
535 -- last. (We don't have an operation for testing whether a key is
536 -- "equal to or greater than" a node, so we must say instead "not
537 -- less than", which is equivalent.)
539 if Hint = 0 then -- largest
540 if Tree.Last = 0 then
541 Insert_Post (Tree, 0, False, Node);
542 elsif Is_Less_Key_Node (Key, N (Tree.Last)) then
543 Unconditional_Insert_Sans_Hint (Tree, Key, Node);
545 Insert_Post (Tree, Tree.Last, False, Node);
551 pragma Assert (Tree.Length > 0);
553 -- We decide here whether to insert the new node prior to the
554 -- hint. Key could be equivalent to the hint, so in theory we
555 -- could write the following test as "not greater than" (same as
556 -- "less than or equal to"). If Key were equivalent to the hint,
557 -- that would mean that the new node gets inserted before an
558 -- equivalent node. That wouldn't break any container invariants,
559 -- but our rule above says that new nodes always get inserted
560 -- after equivalent nodes. So here we test whether Key is both
561 -- less than the hint and equal to or greater than the hint's
562 -- previous neighbor, and if so insert it before the hint.
564 if Is_Less_Key_Node (Key, N (Hint)) then
566 Before : constant Count_Type := Ops.Previous (Tree, Hint);
569 Insert_Post (Tree, Hint, True, Node);
570 elsif Is_Less_Key_Node (Key, N (Before)) then
571 Unconditional_Insert_Sans_Hint (Tree, Key, Node);
572 elsif Ops.Right (N (Before)) = 0 then
573 Insert_Post (Tree, Before, False, Node);
575 Insert_Post (Tree, Hint, True, Node);
582 -- We know that Key isn't less than the hint, so it must be equal
583 -- or greater. So we just test whether Key is less than or equal
584 -- to (same as "not greater than") the hint's next neighbor, and
585 -- if so insert it after the hint.
588 After : constant Count_Type := Ops.Next (Tree, Hint);
591 Insert_Post (Tree, Hint, False, Node);
592 elsif Is_Greater_Key_Node (Key, N (After)) then
593 Unconditional_Insert_Sans_Hint (Tree, Key, Node);
594 elsif Ops.Right (N (Hint)) = 0 then
595 Insert_Post (Tree, Hint, False, Node);
597 Insert_Post (Tree, After, True, Node);
600 end Generic_Unconditional_Insert_With_Hint;
607 (Tree : Tree_Type'Class;
608 Key : Key_Type) return Count_Type
612 N : Nodes_Type renames Tree.Nodes;
619 if Is_Less_Key_Node (Key, N (X)) then
621 X := Ops.Left (N (X));
623 X := Ops.Right (N (X));
630 end Ada.Containers.Red_Black_Trees.Generic_Bounded_Keys;