1 ------------------------------------------------------------------------------
3 -- GNAT LIBRARY COMPONENTS --
5 -- A D A . C O N T A I N E R S . R E D _ B L A C K _ T R E E S . --
6 -- G E N E R I C _ K E Y S --
10 -- Copyright (C) 2004-2006, Free Software Foundation, Inc. --
12 -- GNAT is free software; you can redistribute it and/or modify it under --
13 -- terms of the GNU General Public License as published by the Free Soft- --
14 -- ware Foundation; either version 2, or (at your option) any later ver- --
15 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
16 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
17 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
18 -- for more details. You should have received a copy of the GNU General --
19 -- Public License distributed with GNAT; see file COPYING. If not, write --
20 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
21 -- Boston, MA 02110-1301, USA. --
23 -- As a special exception, if other files instantiate generics from this --
24 -- unit, or you link this unit with other files to produce an executable, --
25 -- this unit does not by itself cause the resulting executable to be --
26 -- covered by the GNU General Public License. This exception does not --
27 -- however invalidate any other reasons why the executable file might be --
28 -- covered by the GNU Public License. --
30 -- This unit was originally developed by Matthew J Heaney. --
31 ------------------------------------------------------------------------------
33 package body Ada
.Containers
.Red_Black_Trees
.Generic_Keys
is
35 package Ops
renames Tree_Operations
;
43 function Ceiling
(Tree
: Tree_Type
; Key
: Key_Type
) return Node_Access
is
50 if Is_Greater_Key_Node
(Key
, X
) then
65 function Find
(Tree
: Tree_Type
; Key
: Key_Type
) return Node_Access
is
72 if Is_Greater_Key_Node
(Key
, X
) then
84 if Is_Less_Key_Node
(Key
, Y
) then
95 function Floor
(Tree
: Tree_Type
; Key
: Key_Type
) return Node_Access
is
102 if Is_Less_Key_Node
(Key
, X
) then
113 --------------------------------
114 -- Generic_Conditional_Insert --
115 --------------------------------
117 procedure Generic_Conditional_Insert
118 (Tree
: in out Tree_Type
;
120 Node
: out Node_Access
;
121 Inserted
: out Boolean)
123 Y
: Node_Access
:= null;
124 X
: Node_Access
:= Tree
.Root
;
130 Inserted
:= Is_Less_Key_Node
(Key
, X
);
139 -- If Inserted is True, then this means either that Tree is
140 -- empty, or there was a least one node (strictly) greater than
141 -- Key. Otherwise, it means that Key is equal to or greater than
145 if Y
= Tree
.First
then
146 Insert_Post
(Tree
, Y
, True, Node
);
150 Node
:= Ops
.Previous
(Y
);
156 -- Here Node has a value that is less than or equal to Key. We
157 -- now have to resolve whether Key is equal to or greater than
158 -- Node, which determines whether the insertion succeeds.
160 if Is_Greater_Key_Node
(Key
, Node
) then
161 Insert_Post
(Tree
, Y
, Inserted
, Node
);
167 end Generic_Conditional_Insert
;
169 ------------------------------------------
170 -- Generic_Conditional_Insert_With_Hint --
171 ------------------------------------------
173 procedure Generic_Conditional_Insert_With_Hint
174 (Tree
: in out Tree_Type
;
175 Position
: Node_Access
;
177 Node
: out Node_Access
;
178 Inserted
: out Boolean)
181 -- The purpose of a hint is to avoid a search from the root of
182 -- tree. If we have it hint it means we only need to traverse the
183 -- subtree rooted at the hint to find the nearest neighbor. Note
184 -- that finding the neighbor means merely walking the tree; this
185 -- is not a search and the only comparisons that occur are with
186 -- the hint and its neighbor.
188 -- If Position is null, this is intepreted to mean that Key is
189 -- large relative to the nodes in the tree. If the tree is empty,
190 -- or Key is greater than the last node in the tree, then we're
191 -- done; otherwise the hint was "wrong" and we must search.
193 if Position
= null then -- largest
195 or else Is_Greater_Key_Node
(Key
, Tree
.Last
)
197 Insert_Post
(Tree
, Tree
.Last
, False, Node
);
200 Conditional_Insert_Sans_Hint
(Tree
, Key
, Node
, Inserted
);
206 pragma Assert
(Tree
.Length
> 0);
208 -- A hint can either name the node that immediately follows Key,
209 -- or immediately precedes Key. We first test whether Key is is
210 -- less than the hint, and if so we compare Key to the node that
211 -- precedes the hint. If Key is both less than the hint and
212 -- greater than the hint's preceding neighbor, then we're done;
213 -- otherwise we must search.
215 -- Note also that a hint can either be an anterior node or a leaf
216 -- node. A new node is always inserted at the bottom of the tree
217 -- (at least prior to rebalancing), becoming the new left or
218 -- right child of leaf node (which prior to the insertion must
219 -- necessarily be null, since this is a leaf). If the hint names
220 -- an anterior node then its neighbor must be a leaf, and so
221 -- (here) we insert after the neighbor. If the hint names a leaf
222 -- then its neighbor must be anterior and so we insert before the
225 if Is_Less_Key_Node
(Key
, Position
) then
227 Before
: constant Node_Access
:= Ops
.Previous
(Position
);
230 if Before
= null then
231 Insert_Post
(Tree
, Tree
.First
, True, Node
);
234 elsif Is_Greater_Key_Node
(Key
, Before
) then
235 if Ops
.Right
(Before
) = null then
236 Insert_Post
(Tree
, Before
, False, Node
);
238 Insert_Post
(Tree
, Position
, True, Node
);
244 Conditional_Insert_Sans_Hint
(Tree
, Key
, Node
, Inserted
);
251 -- We know that Key isn't less than the hint so we try again,
252 -- this time to see if it's greater than the hint. If so we
253 -- compare Key to the node that follows the hint. If Key is both
254 -- greater than the hint and less than the hint's next neighbor,
255 -- then we're done; otherwise we must search.
257 if Is_Greater_Key_Node
(Key
, Position
) then
259 After
: constant Node_Access
:= Ops
.Next
(Position
);
263 Insert_Post
(Tree
, Tree
.Last
, False, Node
);
266 elsif Is_Less_Key_Node
(Key
, After
) then
267 if Ops
.Right
(Position
) = null then
268 Insert_Post
(Tree
, Position
, False, Node
);
270 Insert_Post
(Tree
, After
, True, Node
);
276 Conditional_Insert_Sans_Hint
(Tree
, Key
, Node
, Inserted
);
283 -- We know that Key is neither less than the hint nor greater
284 -- than the hint, and that's the definition of equivalence.
285 -- There's nothing else we need to do, since a search would just
286 -- reach the same conclusion.
290 end Generic_Conditional_Insert_With_Hint
;
292 -------------------------
293 -- Generic_Insert_Post --
294 -------------------------
296 procedure Generic_Insert_Post
297 (Tree
: in out Tree_Type
;
303 if Tree
.Length
= Count_Type
'Last then
304 raise Constraint_Error
with "too many elements";
307 if Tree
.Busy
> 0 then
308 raise Program_Error
with
309 "attempt to tamper with cursors (container is busy)";
313 pragma Assert
(Z
/= null);
314 pragma Assert
(Ops
.Color
(Z
) = Red
);
317 pragma Assert
(Tree
.Length
= 0);
318 pragma Assert
(Tree
.Root
= null);
319 pragma Assert
(Tree
.First
= null);
320 pragma Assert
(Tree
.Last
= null);
327 pragma Assert
(Ops
.Left
(Y
) = null);
331 if Y
= Tree
.First
then
336 pragma Assert
(Ops
.Right
(Y
) = null);
338 Ops
.Set_Right
(Y
, Z
);
340 if Y
= Tree
.Last
then
345 Ops
.Set_Parent
(Z
, Y
);
346 Ops
.Rebalance_For_Insert
(Tree
, Z
);
347 Tree
.Length
:= Tree
.Length
+ 1;
348 end Generic_Insert_Post
;
350 -----------------------
351 -- Generic_Iteration --
352 -----------------------
354 procedure Generic_Iteration
358 procedure Iterate
(Node
: Node_Access
);
364 procedure Iterate
(Node
: Node_Access
) is
369 if Is_Less_Key_Node
(Key
, N
) then
371 elsif Is_Greater_Key_Node
(Key
, N
) then
374 Iterate
(Ops
.Left
(N
));
381 -- Start of processing for Generic_Iteration
385 end Generic_Iteration
;
387 -------------------------------
388 -- Generic_Reverse_Iteration --
389 -------------------------------
391 procedure Generic_Reverse_Iteration
395 procedure Iterate
(Node
: Node_Access
);
401 procedure Iterate
(Node
: Node_Access
) is
406 if Is_Less_Key_Node
(Key
, N
) then
408 elsif Is_Greater_Key_Node
(Key
, N
) then
411 Iterate
(Ops
.Right
(N
));
418 -- Start of processing for Generic_Reverse_Iteration
422 end Generic_Reverse_Iteration
;
424 ----------------------------------
425 -- Generic_Unconditional_Insert --
426 ----------------------------------
428 procedure Generic_Unconditional_Insert
429 (Tree
: in out Tree_Type
;
431 Node
: out Node_Access
)
445 Before
:= Is_Less_Key_Node
(Key
, X
);
454 Insert_Post
(Tree
, Y
, Before
, Node
);
455 end Generic_Unconditional_Insert
;
457 --------------------------------------------
458 -- Generic_Unconditional_Insert_With_Hint --
459 --------------------------------------------
461 procedure Generic_Unconditional_Insert_With_Hint
462 (Tree
: in out Tree_Type
;
465 Node
: out Node_Access
)
468 -- There are fewer constraints for an unconditional insertion
469 -- than for a conditional insertion, since we allow duplicate
470 -- keys. So instead of having to check (say) whether Key is
471 -- (strictly) greater than the hint's previous neighbor, here we
472 -- allow Key to be equal to or greater than the previous node.
474 -- There is the issue of what to do if Key is equivalent to the
475 -- hint. Does the new node get inserted before or after the hint?
476 -- We decide that it gets inserted after the hint, reasoning that
477 -- this is consistent with behavior for non-hint insertion, which
478 -- inserts a new node after existing nodes with equivalent keys.
480 -- First we check whether the hint is null, which is interpreted
481 -- to mean that Key is large relative to existing nodes.
482 -- Following our rule above, if Key is equal to or greater than
483 -- the last node, then we insert the new node immediately after
484 -- last. (We don't have an operation for testing whether a key is
485 -- "equal to or greater than" a node, so we must say instead "not
486 -- less than", which is equivalent.)
488 if Hint
= null then -- largest
489 if Tree
.Last
= null then
490 Insert_Post
(Tree
, null, False, Node
);
491 elsif Is_Less_Key_Node
(Key
, Tree
.Last
) then
492 Unconditional_Insert_Sans_Hint
(Tree
, Key
, Node
);
494 Insert_Post
(Tree
, Tree
.Last
, False, Node
);
500 pragma Assert
(Tree
.Length
> 0);
502 -- We decide here whether to insert the new node prior to the
503 -- hint. Key could be equivalent to the hint, so in theory we
504 -- could write the following test as "not greater than" (same as
505 -- "less than or equal to"). If Key were equivalent to the hint,
506 -- that would mean that the new node gets inserted before an
507 -- equivalent node. That wouldn't break any container invariants,
508 -- but our rule above says that new nodes always get inserted
509 -- after equivalent nodes. So here we test whether Key is both
510 -- less than the hint and and equal to or greater than the hint's
511 -- previous neighbor, and if so insert it before the hint.
513 if Is_Less_Key_Node
(Key
, Hint
) then
515 Before
: constant Node_Access
:= Ops
.Previous
(Hint
);
517 if Before
= null then
518 Insert_Post
(Tree
, Hint
, True, Node
);
519 elsif Is_Less_Key_Node
(Key
, Before
) then
520 Unconditional_Insert_Sans_Hint
(Tree
, Key
, Node
);
521 elsif Ops
.Right
(Before
) = null then
522 Insert_Post
(Tree
, Before
, False, Node
);
524 Insert_Post
(Tree
, Hint
, True, Node
);
531 -- We know that Key isn't less than the hint, so it must be equal
532 -- or greater. So we just test whether Key is less than or equal
533 -- to (same as "not greater than") the hint's next neighbor, and
534 -- if so insert it after the hint.
537 After
: constant Node_Access
:= Ops
.Next
(Hint
);
540 Insert_Post
(Tree
, Hint
, False, Node
);
541 elsif Is_Greater_Key_Node
(Key
, After
) then
542 Unconditional_Insert_Sans_Hint
(Tree
, Key
, Node
);
543 elsif Ops
.Right
(Hint
) = null then
544 Insert_Post
(Tree
, Hint
, False, Node
);
546 Insert_Post
(Tree
, After
, True, Node
);
549 end Generic_Unconditional_Insert_With_Hint
;
557 Key
: Key_Type
) return Node_Access
565 if Is_Less_Key_Node
(Key
, X
) then
576 end Ada
.Containers
.Red_Black_Trees
.Generic_Keys
;