1 | /*************************************************************************** |
2 | * _ _ ____ _ |
3 | * Project ___| | | | _ \| | |
4 | * / __| | | | |_) | | |
5 | * | (__| |_| | _ <| |___ |
6 | * \___|\___/|_| \_\_____| |
7 | * |
8 | * Copyright (C) 1997 - 2019, 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 https://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 "curl_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 | */ |
40 | struct Curl_tree *Curl_splay(struct curltime i, |
41 | struct Curl_tree *t) |
42 | { |
43 | struct Curl_tree N, *l, *r, *y; |
44 | |
45 | if(t == NULL) |
46 | return t; |
47 | N.smaller = N.larger = NULL; |
48 | l = r = &N; |
49 | |
50 | for(;;) { |
51 | long comp = compare(i, t->key); |
52 | if(comp < 0) { |
53 | if(t->smaller == NULL) |
54 | break; |
55 | if(compare(i, t->smaller->key) < 0) { |
56 | y = t->smaller; /* rotate smaller */ |
57 | t->smaller = y->larger; |
58 | y->larger = t; |
59 | t = y; |
60 | if(t->smaller == NULL) |
61 | break; |
62 | } |
63 | r->smaller = t; /* link smaller */ |
64 | r = t; |
65 | t = t->smaller; |
66 | } |
67 | else if(comp > 0) { |
68 | if(t->larger == NULL) |
69 | break; |
70 | if(compare(i, t->larger->key) > 0) { |
71 | y = t->larger; /* rotate larger */ |
72 | t->larger = y->smaller; |
73 | y->smaller = t; |
74 | t = y; |
75 | if(t->larger == NULL) |
76 | break; |
77 | } |
78 | l->larger = t; /* link larger */ |
79 | l = t; |
80 | t = t->larger; |
81 | } |
82 | else |
83 | break; |
84 | } |
85 | |
86 | l->larger = t->smaller; /* assemble */ |
87 | r->smaller = t->larger; |
88 | t->smaller = N.larger; |
89 | t->larger = N.smaller; |
90 | |
91 | return t; |
92 | } |
93 | |
94 | /* Insert key i into the tree t. Return a pointer to the resulting tree or |
95 | * NULL if something went wrong. |
96 | * |
97 | * @unittest: 1309 |
98 | */ |
99 | struct Curl_tree *Curl_splayinsert(struct curltime i, |
100 | struct Curl_tree *t, |
101 | struct Curl_tree *node) |
102 | { |
103 | static const struct curltime KEY_NOTUSED = { |
104 | (time_t)-1, (unsigned int)-1 |
105 | }; /* will *NEVER* appear */ |
106 | |
107 | if(node == NULL) |
108 | return t; |
109 | |
110 | if(t != NULL) { |
111 | t = Curl_splay(i, t); |
112 | if(compare(i, t->key) == 0) { |
113 | /* There already exists a node in the tree with the very same key. Build |
114 | a doubly-linked circular list of nodes. We add the new 'node' struct |
115 | to the end of this list. */ |
116 | |
117 | node->key = KEY_NOTUSED; /* we set the key in the sub node to NOTUSED |
118 | to quickly identify this node as a subnode */ |
119 | node->samen = t; |
120 | node->samep = t->samep; |
121 | t->samep->samen = node; |
122 | t->samep = node; |
123 | |
124 | return t; /* the root node always stays the same */ |
125 | } |
126 | } |
127 | |
128 | if(t == NULL) { |
129 | node->smaller = node->larger = NULL; |
130 | } |
131 | else if(compare(i, t->key) < 0) { |
132 | node->smaller = t->smaller; |
133 | node->larger = t; |
134 | t->smaller = NULL; |
135 | |
136 | } |
137 | else { |
138 | node->larger = t->larger; |
139 | node->smaller = t; |
140 | t->larger = NULL; |
141 | } |
142 | node->key = i; |
143 | |
144 | /* no identical nodes (yet), we are the only one in the list of nodes */ |
145 | node->samen = node; |
146 | node->samep = node; |
147 | return node; |
148 | } |
149 | |
150 | /* Finds and deletes the best-fit node from the tree. Return a pointer to the |
151 | resulting tree. best-fit means the smallest node if it is not larger than |
152 | the key */ |
153 | struct Curl_tree *Curl_splaygetbest(struct curltime i, |
154 | struct Curl_tree *t, |
155 | struct Curl_tree **removed) |
156 | { |
157 | static struct curltime tv_zero = {0, 0}; |
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 | /* find smallest */ |
166 | t = Curl_splay(tv_zero, t); |
167 | if(compare(i, t->key) < 0) { |
168 | /* even the smallest is too big */ |
169 | *removed = NULL; |
170 | return t; |
171 | } |
172 | |
173 | /* FIRST! Check if there is a list with identical keys */ |
174 | x = t->samen; |
175 | if(x != t) { |
176 | /* there is, pick one from the list */ |
177 | |
178 | /* 'x' is the new root node */ |
179 | |
180 | x->key = t->key; |
181 | x->larger = t->larger; |
182 | x->smaller = t->smaller; |
183 | x->samep = t->samep; |
184 | t->samep->samen = x; |
185 | |
186 | *removed = t; |
187 | return x; /* new root */ |
188 | } |
189 | |
190 | /* we splayed the tree to the smallest element, there is no smaller */ |
191 | x = t->larger; |
192 | *removed = t; |
193 | |
194 | return x; |
195 | } |
196 | |
197 | |
198 | /* Deletes the very node we point out from the tree if it's there. Stores a |
199 | * pointer to the new resulting tree in 'newroot'. |
200 | * |
201 | * Returns zero on success and non-zero on errors! |
202 | * When returning error, it does not touch the 'newroot' pointer. |
203 | * |
204 | * NOTE: when the last node of the tree is removed, there's no tree left so |
205 | * 'newroot' will be made to point to NULL. |
206 | * |
207 | * @unittest: 1309 |
208 | */ |
209 | int Curl_splayremovebyaddr(struct Curl_tree *t, |
210 | struct Curl_tree *removenode, |
211 | struct Curl_tree **newroot) |
212 | { |
213 | static const struct curltime KEY_NOTUSED = { |
214 | (time_t)-1, (unsigned int)-1 |
215 | }; /* will *NEVER* appear */ |
216 | struct Curl_tree *x; |
217 | |
218 | if(!t || !removenode) |
219 | return 1; |
220 | |
221 | if(compare(KEY_NOTUSED, removenode->key) == 0) { |
222 | /* Key set to NOTUSED means it is a subnode within a 'same' linked list |
223 | and thus we can unlink it easily. */ |
224 | if(removenode->samen == removenode) |
225 | /* A non-subnode should never be set to KEY_NOTUSED */ |
226 | return 3; |
227 | |
228 | removenode->samep->samen = removenode->samen; |
229 | removenode->samen->samep = removenode->samep; |
230 | |
231 | /* Ensures that double-remove gets caught. */ |
232 | removenode->samen = removenode; |
233 | |
234 | *newroot = t; /* return the same root */ |
235 | return 0; |
236 | } |
237 | |
238 | t = Curl_splay(removenode->key, t); |
239 | |
240 | /* First make sure that we got the same root node as the one we want |
241 | to remove, as otherwise we might be trying to remove a node that |
242 | isn't actually in the tree. |
243 | |
244 | We cannot just compare the keys here as a double remove in quick |
245 | succession of a node with key != KEY_NOTUSED && same != NULL |
246 | could return the same key but a different node. */ |
247 | if(t != removenode) |
248 | return 2; |
249 | |
250 | /* Check if there is a list with identical sizes, as then we're trying to |
251 | remove the root node of a list of nodes with identical keys. */ |
252 | x = t->samen; |
253 | if(x != t) { |
254 | /* 'x' is the new root node, we just make it use the root node's |
255 | smaller/larger links */ |
256 | |
257 | x->key = t->key; |
258 | x->larger = t->larger; |
259 | x->smaller = t->smaller; |
260 | x->samep = t->samep; |
261 | t->samep->samen = x; |
262 | } |
263 | else { |
264 | /* Remove the root node */ |
265 | if(t->smaller == NULL) |
266 | x = t->larger; |
267 | else { |
268 | x = Curl_splay(removenode->key, t->smaller); |
269 | x->larger = t->larger; |
270 | } |
271 | } |
272 | |
273 | *newroot = x; /* store new root pointer */ |
274 | |
275 | return 0; |
276 | } |
277 | |