1/***************************************************************************
2 *                                  _   _ ____  _
3 *  Project                     ___| | | |  _ \| |
4 *                             / __| | | | |_) | |
5 *                            | (__| |_| |  _ <| |___
6 *                             \___|\___/|_| \_\_____|
7 *
8 * Copyright (C) 1997 - 2011, Daniel Stenberg, <daniel@haxx.se>, et al.
9 *
10 * This software is licensed as described in the file COPYING, which
11 * you should have received as part of this distribution. The terms
12 * are also available at http://curl.haxx.se/docs/copyright.html.
13 *
14 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
15 * copies of the Software, and permit persons to whom the Software is
16 * furnished to do so, under the terms of the COPYING file.
17 *
18 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
19 * KIND, either express or implied.
20 *
21 ***************************************************************************/
22
23#include "setup.h"
24
25#include "splay.h"
26
27/*
28 * This macro compares two node keys i and j and returns:
29 *
30 *  negative value: when i is smaller than j
31 *  zero          : when i is equal   to   j
32 *  positive when : when i is larger  than j
33 */
34#define compare(i,j) Curl_splaycomparekeys((i),(j))
35
36/*
37 * Splay using the key i (which may or may not be in the tree.) The starting
38 * root is t.
39 */
40struct Curl_tree *Curl_splay(struct timeval i,
41                             struct Curl_tree *t)
42{
43  struct Curl_tree N, *l, *r, *y;
44  long comp;
45
46  if(t == NULL)
47    return t;
48  N.smaller = N.larger = NULL;
49  l = r = &N;
50
51  for(;;) {
52    comp = compare(i, t->key);
53    if(comp < 0) {
54      if(t->smaller == NULL)
55        break;
56      if(compare(i, t->smaller->key) < 0) {
57        y = t->smaller;                           /* rotate smaller */
58        t->smaller = y->larger;
59        y->larger = t;
60        t = y;
61        if(t->smaller == NULL)
62          break;
63      }
64      r->smaller = t;                               /* link smaller */
65      r = t;
66      t = t->smaller;
67    }
68    else if(comp > 0) {
69      if(t->larger == NULL)
70        break;
71      if(compare(i, t->larger->key) > 0) {
72        y = t->larger;                          /* rotate larger */
73        t->larger = y->smaller;
74        y->smaller = t;
75        t = y;
76        if(t->larger == NULL)
77          break;
78      }
79      l->larger = t;                              /* link larger */
80      l = t;
81      t = t->larger;
82    }
83    else
84      break;
85  }
86
87  l->larger = t->smaller;                                /* assemble */
88  r->smaller = t->larger;
89  t->smaller = N.larger;
90  t->larger = N.smaller;
91
92  return t;
93}
94
95/* Insert key i into the tree t.  Return a pointer to the resulting tree or
96 * NULL if something went wrong.
97 *
98 * @unittest: 1309
99 */
100struct Curl_tree *Curl_splayinsert(struct timeval i,
101                                   struct Curl_tree *t,
102                                   struct Curl_tree *node)
103{
104  static struct timeval KEY_NOTUSED = {-1,-1}; /* will *NEVER* appear */
105
106  if(node == NULL)
107    return t;
108
109  if(t != NULL) {
110    t = Curl_splay(i,t);
111    if(compare(i, t->key)==0) {
112      /* There already exists a node in the tree with the very same key. Build
113         a linked list of nodes. We make the new 'node' struct the new master
114         node and make the previous node the first one in the 'same' list. */
115
116      node->same = t;
117      node->key = i;
118      node->smaller = t->smaller;
119      node->larger = t->larger;
120
121      t->smaller = node; /* in the sub node for this same key, we use the
122                            smaller pointer to point back to the master
123                            node */
124
125      t->key = KEY_NOTUSED; /* and we set the key in the sub node to NOTUSED
126                               to quickly identify this node as a subnode */
127
128      return node; /* new root node */
129    }
130  }
131
132  if(t == NULL) {
133    node->smaller = node->larger = NULL;
134  }
135  else if(compare(i, t->key) < 0) {
136    node->smaller = t->smaller;
137    node->larger = t;
138    t->smaller = NULL;
139
140  }
141  else {
142    node->larger = t->larger;
143    node->smaller = t;
144    t->larger = NULL;
145  }
146  node->key = i;
147
148  node->same = NULL; /* no identical node (yet) */
149  return node;
150}
151
152/* Finds and deletes the best-fit node from the tree. Return a pointer to the
153   resulting tree.  best-fit means the node with the given or lower key */
154struct Curl_tree *Curl_splaygetbest(struct timeval i,
155                                    struct Curl_tree *t,
156                                    struct Curl_tree **removed)
157{
158  struct Curl_tree *x;
159
160  if(!t) {
161    *removed = NULL; /* none removed since there was no root */
162    return NULL;
163  }
164
165  t = Curl_splay(i,t);
166  if(compare(i, t->key) < 0) {
167    /* too big node, try the smaller chain */
168    if(t->smaller)
169      t=Curl_splay(t->smaller->key, t);
170    else {
171      /* fail */
172      *removed = NULL;
173      return t;
174    }
175  }
176
177  if(compare(i, t->key) >= 0) {               /* found it */
178    /* FIRST! Check if there is a list with identical keys */
179    x = t->same;
180    if(x) {
181      /* there is, pick one from the list */
182
183      /* 'x' is the new root node */
184
185      x->key = t->key;
186      x->larger = t->larger;
187      x->smaller = t->smaller;
188
189      *removed = t;
190      return x; /* new root */
191    }
192
193    if(t->smaller == NULL) {
194      x = t->larger;
195    }
196    else {
197      x = Curl_splay(i, t->smaller);
198      x->larger = t->larger;
199    }
200    *removed = t;
201
202    return x;
203  }
204  else {
205    *removed = NULL; /* no match */
206    return t;        /* It wasn't there */
207  }
208}
209
210
211/* Deletes the very node we point out from the tree if it's there. Stores a
212 * pointer to the new resulting tree in 'newroot'.
213 *
214 * Returns zero on success and non-zero on errors! TODO: document error codes.
215 * When returning error, it does not touch the 'newroot' pointer.
216 *
217 * NOTE: when the last node of the tree is removed, there's no tree left so
218 * 'newroot' will be made to point to NULL.
219 *
220 * @unittest: 1309
221 */
222int Curl_splayremovebyaddr(struct Curl_tree *t,
223                           struct Curl_tree *removenode,
224                           struct Curl_tree **newroot)
225{
226  static struct timeval KEY_NOTUSED = {-1,-1}; /* will *NEVER* appear */
227  struct Curl_tree *x;
228
229  if(!t || !removenode)
230    return 1;
231
232  if(compare(KEY_NOTUSED, removenode->key) == 0) {
233    /* Key set to NOTUSED means it is a subnode within a 'same' linked list
234       and thus we can unlink it easily. The 'smaller' link of a subnode
235       links to the parent node. */
236    if(removenode->smaller == NULL)
237      return 3;
238
239    removenode->smaller->same = removenode->same;
240    if(removenode->same)
241      removenode->same->smaller = removenode->smaller;
242
243    /* Ensures that double-remove gets caught. */
244    removenode->smaller = NULL;
245
246    /* voila, we're done! */
247    *newroot = t; /* return the same root */
248    return 0;
249  }
250
251  t = Curl_splay(removenode->key, t);
252
253  /* First make sure that we got the same root node as the one we want
254     to remove, as otherwise we might be trying to remove a node that
255     isn't actually in the tree.
256
257     We cannot just compare the keys here as a double remove in quick
258     succession of a node with key != KEY_NOTUSED && same != NULL
259     could return the same key but a different node. */
260  if(t != removenode)
261    return 2;
262
263  /* Check if there is a list with identical sizes, as then we're trying to
264     remove the root node of a list of nodes with identical keys. */
265  x = t->same;
266  if(x) {
267    /* 'x' is the new root node, we just make it use the root node's
268       smaller/larger links */
269
270    x->key = t->key;
271    x->larger = t->larger;
272    x->smaller = t->smaller;
273  }
274  else {
275    /* Remove the root node */
276    if(t->smaller == NULL)
277      x = t->larger;
278    else {
279      x = Curl_splay(removenode->key, t->smaller);
280      x->larger = t->larger;
281    }
282  }
283
284  *newroot = x; /* store new root pointer */
285
286  return 0;
287}
288
289