1 ------------------------------------------------------------------------------
3 -- GNAT LIBRARY COMPONENTS --
5 -- ADA.CONTAINERS.RED_BLACK_TREES.GENERIC_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_Keys is
32 package Ops renames Tree_Operations;
40 function Ceiling (Tree : Tree_Type; Key : Key_Type) return Node_Access is
47 if Is_Greater_Key_Node (Key, X) then
62 function Find (Tree : Tree_Type; Key : Key_Type) return Node_Access is
69 if Is_Greater_Key_Node (Key, X) then
81 if Is_Less_Key_Node (Key, Y) then
92 function Floor (Tree : Tree_Type; Key : Key_Type) return Node_Access is
99 if Is_Less_Key_Node (Key, X) then
110 --------------------------------
111 -- Generic_Conditional_Insert --
112 --------------------------------
114 procedure Generic_Conditional_Insert
115 (Tree : in out Tree_Type;
117 Node : out Node_Access;
118 Inserted : out Boolean)
120 Y : Node_Access := null;
121 X : Node_Access := Tree.Root;
124 -- This is a "conditional" insertion, meaning that the insertion request
125 -- can "fail" in the sense that no new node is created. If the Key is
126 -- equivalent to an existing node, then we return the existing node and
127 -- Inserted is set to False. Otherwise, we allocate a new node (via
128 -- Insert_Post) and Inserted is set to True.
130 -- Note that we are testing for equivalence here, not equality. Key must
131 -- be strictly less than its next neighbor, and strictly greater than
132 -- its previous neighbor, in order for the conditional insertion to
135 -- We search the tree to find the nearest neighbor of Key, which is
136 -- either the smallest node greater than Key (Inserted is True), or the
137 -- largest node less or equivalent to Key (Inserted is False).
142 Inserted := Is_Less_Key_Node (Key, X);
143 X := (if Inserted then Ops.Left (X) else Ops.Right (X));
148 -- Either Tree is empty, or Key is less than Y. If Y is the first
149 -- node in the tree, then there are no other nodes that we need to
150 -- search for, and we insert a new node into the tree.
152 if Y = Tree.First then
153 Insert_Post (Tree, Y, True, Node);
157 -- Y is the next nearest-neighbor of Key. We know that Key is not
158 -- equivalent to Y (because Key is strictly less than Y), so we move
159 -- to the previous node, the nearest-neighbor just smaller or
160 -- equivalent to Key.
162 Node := Ops.Previous (Y);
165 -- Y is the previous nearest-neighbor of Key. We know that Key is not
166 -- less than Y, which means either that Key is equivalent to Y, or
172 -- Key is equivalent to or greater than Node. We must resolve which is
173 -- the case, to determine whether the conditional insertion succeeds.
175 if Is_Greater_Key_Node (Key, Node) then
177 -- Key is strictly greater than Node, which means that Key is not
178 -- equivalent to Node. In this case, the insertion succeeds, and we
179 -- insert a new node into the tree.
181 Insert_Post (Tree, Y, Inserted, Node);
186 -- Key is equivalent to Node. This is a conditional insertion, so we do
187 -- not insert a new node in this case. We return the existing node and
188 -- report that no insertion has occurred.
191 end Generic_Conditional_Insert;
193 ------------------------------------------
194 -- Generic_Conditional_Insert_With_Hint --
195 ------------------------------------------
197 procedure Generic_Conditional_Insert_With_Hint
198 (Tree : in out Tree_Type;
199 Position : Node_Access;
201 Node : out Node_Access;
202 Inserted : out Boolean)
205 -- The purpose of a hint is to avoid a search from the root of
206 -- tree. If we have it hint it means we only need to traverse the
207 -- subtree rooted at the hint to find the nearest neighbor. Note
208 -- that finding the neighbor means merely walking the tree; this
209 -- is not a search and the only comparisons that occur are with
210 -- the hint and its neighbor.
212 -- If Position is null, this is interpreted to mean that Key is
213 -- large relative to the nodes in the tree. If the tree is empty,
214 -- or Key is greater than the last node in the tree, then we're
215 -- done; otherwise the hint was "wrong" and we must search.
217 if Position = null then -- largest
219 or else Is_Greater_Key_Node (Key, Tree.Last)
221 Insert_Post (Tree, Tree.Last, False, Node);
224 Conditional_Insert_Sans_Hint (Tree, Key, Node, Inserted);
230 pragma Assert (Tree.Length > 0);
232 -- A hint can either name the node that immediately follows Key,
233 -- or immediately precedes Key. We first test whether Key is
234 -- less than the hint, and if so we compare Key to the node that
235 -- precedes the hint. If Key is both less than the hint and
236 -- greater than the hint's preceding neighbor, then we're done;
237 -- otherwise we must search.
239 -- Note also that a hint can either be an anterior node or a leaf
240 -- node. A new node is always inserted at the bottom of the tree
241 -- (at least prior to rebalancing), becoming the new left or
242 -- right child of leaf node (which prior to the insertion must
243 -- necessarily be null, since this is a leaf). If the hint names
244 -- an anterior node then its neighbor must be a leaf, and so
245 -- (here) we insert after the neighbor. If the hint names a leaf
246 -- then its neighbor must be anterior and so we insert before the
249 if Is_Less_Key_Node (Key, Position) then
251 Before : constant Node_Access := Ops.Previous (Position);
254 if Before = null then
255 Insert_Post (Tree, Tree.First, True, Node);
258 elsif Is_Greater_Key_Node (Key, Before) then
259 if Ops.Right (Before) = null then
260 Insert_Post (Tree, Before, False, Node);
262 Insert_Post (Tree, Position, True, Node);
268 Conditional_Insert_Sans_Hint (Tree, Key, Node, Inserted);
275 -- We know that Key isn't less than the hint so we try again,
276 -- this time to see if it's greater than the hint. If so we
277 -- compare Key to the node that follows the hint. If Key is both
278 -- greater than the hint and less than the hint's next neighbor,
279 -- then we're done; otherwise we must search.
281 if Is_Greater_Key_Node (Key, Position) then
283 After : constant Node_Access := Ops.Next (Position);
287 Insert_Post (Tree, Tree.Last, False, Node);
290 elsif Is_Less_Key_Node (Key, After) then
291 if Ops.Right (Position) = null then
292 Insert_Post (Tree, Position, False, Node);
294 Insert_Post (Tree, After, True, Node);
300 Conditional_Insert_Sans_Hint (Tree, Key, Node, Inserted);
307 -- We know that Key is neither less than the hint nor greater
308 -- than the hint, and that's the definition of equivalence.
309 -- There's nothing else we need to do, since a search would just
310 -- reach the same conclusion.
314 end Generic_Conditional_Insert_With_Hint;
316 -------------------------
317 -- Generic_Insert_Post --
318 -------------------------
320 procedure Generic_Insert_Post
321 (Tree : in out Tree_Type;
327 if Tree.Length = Count_Type'Last then
328 raise Constraint_Error with "too many elements";
331 if Tree.Busy > 0 then
332 raise Program_Error with
333 "attempt to tamper with cursors (container is busy)";
337 pragma Assert (Z /= null);
338 pragma Assert (Ops.Color (Z) = Red);
341 pragma Assert (Tree.Length = 0);
342 pragma Assert (Tree.Root = null);
343 pragma Assert (Tree.First = null);
344 pragma Assert (Tree.Last = null);
351 pragma Assert (Ops.Left (Y) = null);
355 if Y = Tree.First then
360 pragma Assert (Ops.Right (Y) = null);
362 Ops.Set_Right (Y, Z);
364 if Y = Tree.Last then
369 Ops.Set_Parent (Z, Y);
370 Ops.Rebalance_For_Insert (Tree, Z);
371 Tree.Length := Tree.Length + 1;
372 end Generic_Insert_Post;
374 -----------------------
375 -- Generic_Iteration --
376 -----------------------
378 procedure Generic_Iteration
382 procedure Iterate (Node : Node_Access);
388 procedure Iterate (Node : Node_Access) is
393 if Is_Less_Key_Node (Key, N) then
395 elsif Is_Greater_Key_Node (Key, N) then
398 Iterate (Ops.Left (N));
405 -- Start of processing for Generic_Iteration
409 end Generic_Iteration;
411 -------------------------------
412 -- Generic_Reverse_Iteration --
413 -------------------------------
415 procedure Generic_Reverse_Iteration
419 procedure Iterate (Node : Node_Access);
425 procedure Iterate (Node : Node_Access) is
430 if Is_Less_Key_Node (Key, N) then
432 elsif Is_Greater_Key_Node (Key, N) then
435 Iterate (Ops.Right (N));
442 -- Start of processing for Generic_Reverse_Iteration
446 end Generic_Reverse_Iteration;
448 ----------------------------------
449 -- Generic_Unconditional_Insert --
450 ----------------------------------
452 procedure Generic_Unconditional_Insert
453 (Tree : in out Tree_Type;
455 Node : out Node_Access)
469 Before := Is_Less_Key_Node (Key, X);
470 X := (if Before then Ops.Left (X) else Ops.Right (X));
473 Insert_Post (Tree, Y, Before, Node);
474 end Generic_Unconditional_Insert;
476 --------------------------------------------
477 -- Generic_Unconditional_Insert_With_Hint --
478 --------------------------------------------
480 procedure Generic_Unconditional_Insert_With_Hint
481 (Tree : in out Tree_Type;
484 Node : out Node_Access)
487 -- There are fewer constraints for an unconditional insertion
488 -- than for a conditional insertion, since we allow duplicate
489 -- keys. So instead of having to check (say) whether Key is
490 -- (strictly) greater than the hint's previous neighbor, here we
491 -- allow Key to be equal to or greater than the previous node.
493 -- There is the issue of what to do if Key is equivalent to the
494 -- hint. Does the new node get inserted before or after the hint?
495 -- We decide that it gets inserted after the hint, reasoning that
496 -- this is consistent with behavior for non-hint insertion, which
497 -- inserts a new node after existing nodes with equivalent keys.
499 -- First we check whether the hint is null, which is interpreted
500 -- to mean that Key is large relative to existing nodes.
501 -- Following our rule above, if Key is equal to or greater than
502 -- the last node, then we insert the new node immediately after
503 -- last. (We don't have an operation for testing whether a key is
504 -- "equal to or greater than" a node, so we must say instead "not
505 -- less than", which is equivalent.)
507 if Hint = null then -- largest
508 if Tree.Last = null then
509 Insert_Post (Tree, null, False, Node);
510 elsif Is_Less_Key_Node (Key, Tree.Last) then
511 Unconditional_Insert_Sans_Hint (Tree, Key, Node);
513 Insert_Post (Tree, Tree.Last, False, Node);
519 pragma Assert (Tree.Length > 0);
521 -- We decide here whether to insert the new node prior to the
522 -- hint. Key could be equivalent to the hint, so in theory we
523 -- could write the following test as "not greater than" (same as
524 -- "less than or equal to"). If Key were equivalent to the hint,
525 -- that would mean that the new node gets inserted before an
526 -- equivalent node. That wouldn't break any container invariants,
527 -- but our rule above says that new nodes always get inserted
528 -- after equivalent nodes. So here we test whether Key is both
529 -- less than the hint and equal to or greater than the hint's
530 -- previous neighbor, and if so insert it before the hint.
532 if Is_Less_Key_Node (Key, Hint) then
534 Before : constant Node_Access := Ops.Previous (Hint);
536 if Before = null then
537 Insert_Post (Tree, Hint, True, Node);
538 elsif Is_Less_Key_Node (Key, Before) then
539 Unconditional_Insert_Sans_Hint (Tree, Key, Node);
540 elsif Ops.Right (Before) = null then
541 Insert_Post (Tree, Before, False, Node);
543 Insert_Post (Tree, Hint, True, Node);
550 -- We know that Key isn't less than the hint, so it must be equal
551 -- or greater. So we just test whether Key is less than or equal
552 -- to (same as "not greater than") the hint's next neighbor, and
553 -- if so insert it after the hint.
556 After : constant Node_Access := Ops.Next (Hint);
559 Insert_Post (Tree, Hint, False, Node);
560 elsif Is_Greater_Key_Node (Key, After) then
561 Unconditional_Insert_Sans_Hint (Tree, Key, Node);
562 elsif Ops.Right (Hint) = null then
563 Insert_Post (Tree, Hint, False, Node);
565 Insert_Post (Tree, After, True, Node);
568 end Generic_Unconditional_Insert_With_Hint;
576 Key : Key_Type) return Node_Access
584 if Is_Less_Key_Node (Key, X) then
595 end Ada.Containers.Red_Black_Trees.Generic_Keys;