Commit | Line | Data |
---|---|---|
059ec3d9 PH |
1 | /************************************************* |
2 | * Exim - an Internet mail transport agent * | |
3 | *************************************************/ | |
4 | ||
3386088d | 5 | /* Copyright (c) University of Cambridge 1995 - 2015 */ |
059ec3d9 PH |
6 | /* See the file NOTICE for conditions of use and distribution. */ |
7 | ||
8 | /* Functions for maintaining binary balanced trees and some associated | |
9 | functions as well. */ | |
10 | ||
11 | ||
12 | #include "exim.h" | |
13 | ||
14 | ||
15 | ||
16 | ||
17 | /************************************************* | |
18 | * Add entry to non-recipients tree * | |
19 | *************************************************/ | |
20 | ||
21 | /* Duplicates are just discarded. | |
22 | ||
23 | Arguments: | |
24 | s string to add | |
25 | ||
26 | Returns: nothing | |
27 | */ | |
28 | ||
29 | void | |
30 | tree_add_nonrecipient(uschar *s) | |
31 | { | |
32 | tree_node *node = store_get(sizeof(tree_node) + Ustrlen(s)); | |
33 | Ustrcpy(node->name, s); | |
34 | node->data.ptr = NULL; | |
35 | if (!tree_insertnode(&tree_nonrecipients, node)) store_reset(node); | |
36 | } | |
37 | ||
38 | ||
39 | ||
40 | /************************************************* | |
41 | * Add entry to duplicates tree * | |
42 | *************************************************/ | |
43 | ||
44 | /* Duplicates are just discarded. | |
45 | ||
46 | Argument: | |
47 | s string to add | |
48 | addr the address is is a duplicate of | |
49 | ||
50 | Returns: nothing | |
51 | */ | |
52 | ||
53 | void | |
54 | tree_add_duplicate(uschar *s, address_item *addr) | |
55 | { | |
56 | tree_node *node = store_get(sizeof(tree_node) + Ustrlen(s)); | |
57 | Ustrcpy(node->name, s); | |
58 | node->data.ptr = addr; | |
59 | if (!tree_insertnode(&tree_duplicates, node)) store_reset(node); | |
60 | } | |
61 | ||
62 | ||
63 | ||
64 | /************************************************* | |
65 | * Add entry to unusable addresses tree * | |
66 | *************************************************/ | |
67 | ||
68 | /* Duplicates are simply discarded. | |
69 | ||
70 | Argument: the host item | |
71 | Returns: nothing | |
72 | */ | |
73 | ||
74 | void | |
75 | tree_add_unusable(host_item *h) | |
76 | { | |
77 | tree_node *node; | |
78 | uschar s[256]; | |
79 | sprintf(CS s, "T:%.200s:%s", h->name, h->address); | |
80 | node = store_get(sizeof(tree_node) + Ustrlen(s)); | |
81 | Ustrcpy(node->name, s); | |
82 | node->data.val = h->why; | |
83 | if (h->status == hstatus_unusable_expired) node->data.val += 256; | |
84 | if (!tree_insertnode(&tree_unusable, node)) store_reset(node); | |
85 | } | |
86 | ||
87 | ||
88 | ||
89 | /************************************************* | |
90 | * Write a tree in re-readable form * | |
91 | *************************************************/ | |
92 | ||
93 | /* This function writes out a tree in a form in which it can | |
94 | easily be re-read. It is used for writing out the non-recipients | |
95 | tree onto the spool, for retrieval at the next retry time. | |
96 | ||
97 | The format is as follows: | |
98 | ||
99 | . If the tree is empty, write one line containing XX. | |
100 | ||
101 | . Otherwise, each node is written, preceded by two letters | |
102 | (Y/N) indicating whether it has left or right children. | |
103 | ||
104 | . The left subtree (if any) then follows, then the right subtree. | |
105 | ||
106 | First, there's an internal recursive subroutine. | |
107 | ||
108 | Arguments: | |
109 | p current node | |
110 | f FILE to write to | |
111 | ||
112 | Returns: nothing | |
113 | */ | |
114 | ||
115 | static void | |
116 | write_tree(tree_node *p, FILE *f) | |
117 | { | |
118 | fprintf(f, "%c%c %s\n", | |
119 | (p->left == NULL)? 'N':'Y', (p->right == NULL)? 'N':'Y', p->name); | |
120 | if (p->left != NULL) write_tree(p->left, f); | |
121 | if (p->right != NULL) write_tree(p->right, f); | |
122 | } | |
123 | ||
124 | /* This is the top-level function, with the same arguments. */ | |
125 | ||
126 | void | |
127 | tree_write(tree_node *p, FILE *f) | |
128 | { | |
129 | if (p == NULL) | |
130 | { | |
131 | fprintf(f, "XX\n"); | |
132 | return; | |
133 | } | |
134 | write_tree(p, f); | |
135 | } | |
136 | ||
137 | ||
138 | ||
139 | ||
140 | ||
141 | /*********************************************************** | |
142 | * Binary Balanced Tree Management Routines * | |
143 | ***********************************************************/ | |
144 | ||
145 | /* This set of routines maintains a balanced binary tree using | |
146 | the algorithm given in Knuth Vol 3 page 455. | |
147 | ||
148 | The routines make use of uschar * pointers as byte pointers, | |
149 | so as to be able to do arithmetic on them, since ANSI Standard | |
150 | C does not permit additions and subtractions on void pointers. */ | |
151 | ||
152 | ||
153 | /************************************************* | |
154 | * Flags and Parameters * | |
155 | *************************************************/ | |
156 | ||
157 | #define tree_lbal 1 /* left subtree is longer */ | |
158 | #define tree_rbal 2 /* right subtree is longer */ | |
159 | #define tree_bmask 3 /* mask for flipping bits */ | |
160 | ||
161 | ||
162 | /************************************************* | |
163 | * Insert a new node into a tree * | |
164 | *************************************************/ | |
165 | ||
166 | /* The node->name field must (obviously) be set, but the other | |
167 | fields need not be initialized. | |
168 | ||
169 | Arguments: | |
170 | treebase pointer to the root of the tree | |
171 | node the note to insert, with name field set | |
172 | ||
173 | Returns: TRUE if node inserted; FALSE if not (duplicate) | |
174 | */ | |
175 | ||
176 | int | |
177 | tree_insertnode(tree_node **treebase, tree_node *node) | |
178 | { | |
179 | tree_node *p = *treebase; | |
180 | tree_node **q, *r, *s, **t; | |
181 | int a; | |
182 | ||
183 | node->left = node->right = NULL; | |
184 | node->balance = 0; | |
185 | ||
186 | /* Deal with an empty tree */ | |
187 | ||
188 | if (p == NULL) | |
189 | { | |
190 | *treebase = node; | |
191 | return TRUE; | |
192 | } | |
193 | ||
194 | /* The tree is not empty. While finding the insertion point, | |
195 | q points to the pointer to p, and t points to the pointer to | |
196 | the potential re-balancing point. */ | |
197 | ||
198 | q = treebase; | |
199 | t = q; | |
200 | ||
201 | /* Loop to search tree for place to insert new node */ | |
202 | ||
203 | for (;;) | |
204 | { | |
205 | int c = Ustrcmp(node->name, p->name); | |
206 | if (c == 0) return FALSE; /* Duplicate node encountered */ | |
207 | ||
208 | /* Deal with climbing down the tree, exiting from the loop | |
209 | when we reach a leaf. */ | |
210 | ||
211 | q = (c > 0)? &(p->right) : &(p->left); | |
212 | p = *q; | |
213 | if (p == NULL) break; | |
214 | ||
215 | /* Save the address of the pointer to the last node en route | |
216 | which has a non-zero balance factor. */ | |
217 | ||
218 | if (p->balance != 0) t = q; | |
219 | } | |
220 | ||
221 | /* When the above loop completes, q points to the pointer to NULL; | |
222 | that is the place at which the new node must be inserted. */ | |
223 | ||
224 | *q = node; | |
225 | ||
226 | /* Set up s as the potential re-balancing point, and r as the | |
227 | next node after it along the route. */ | |
228 | ||
229 | s = *t; | |
230 | r = (Ustrcmp(node->name, s->name) > 0)? s->right : s->left; | |
231 | ||
232 | /* Adjust balance factors along the route from s to node. */ | |
233 | ||
234 | p = r; | |
235 | ||
236 | while (p != node) | |
237 | { | |
238 | if (Ustrcmp(node->name, p->name) < 0) | |
239 | { | |
240 | p->balance = tree_lbal; | |
241 | p = p->left; | |
242 | } | |
243 | else | |
244 | { | |
245 | p->balance = tree_rbal; | |
246 | p = p->right; | |
247 | } | |
248 | } | |
249 | ||
250 | /* Now the World-Famous Balancing Act */ | |
251 | ||
252 | a = (Ustrcmp(node->name, s->name) < 0)? tree_lbal : tree_rbal; | |
253 | ||
254 | if (s->balance == 0) s->balance = (uschar)a; /* The tree has grown higher */ | |
255 | else if (s->balance != (uschar)a) s->balance = 0; /* It's become more balanced */ | |
256 | else /* It's got out of balance */ | |
257 | { | |
258 | /* Perform a single rotation */ | |
259 | ||
260 | if (r->balance == (uschar)a) | |
261 | { | |
262 | p = r; | |
263 | if (a == tree_rbal) | |
264 | { | |
265 | s->right = r->left; | |
266 | r->left = s; | |
267 | } | |
268 | else | |
269 | { | |
270 | s->left = r->right; | |
271 | r->right = s; | |
272 | } | |
273 | s->balance = 0; | |
274 | r->balance = 0; | |
275 | } | |
276 | ||
277 | /* Perform a double rotation There was an occasion when the balancing | |
278 | factors were screwed up by a bug in the code that reads a tree from | |
279 | the spool. In case this ever happens again, check for changing p to NULL | |
280 | and don't do it. It is better to have an unbalanced tree than a crash. */ | |
281 | ||
282 | else | |
283 | { | |
284 | if (a == tree_rbal) | |
285 | { | |
286 | if (r->left == NULL) return TRUE; /* Bail out if tree corrupt */ | |
287 | p = r->left; | |
288 | r->left = p->right; | |
289 | p->right = r; | |
290 | s->right = p->left; | |
291 | p->left = s; | |
292 | } | |
293 | else | |
294 | { | |
295 | if (r->right == NULL) return TRUE; /* Bail out if tree corrupt */ | |
296 | p = r->right; | |
297 | r->right = p->left; | |
298 | p->left = r; | |
299 | s->left = p->right; | |
300 | p->right = s; | |
301 | } | |
302 | ||
303 | s->balance = (p->balance == (uschar)a)? (uschar)(a^tree_bmask) : 0; | |
304 | r->balance = (p->balance == (uschar)(a^tree_bmask))? (uschar)a : 0; | |
305 | p->balance = 0; | |
306 | } | |
307 | ||
308 | /* Finishing touch */ | |
309 | ||
310 | *t = p; | |
311 | } | |
312 | ||
313 | return TRUE; /* Successful insertion */ | |
314 | } | |
315 | ||
316 | ||
317 | ||
318 | /************************************************* | |
319 | * Search tree for node by name * | |
320 | *************************************************/ | |
321 | ||
322 | /* | |
323 | Arguments: | |
324 | p root of tree | |
325 | name key to search for | |
326 | ||
327 | Returns: pointer to node, or NULL if not found | |
328 | */ | |
329 | ||
330 | tree_node * | |
55414b25 | 331 | tree_search(tree_node *p, const uschar *name) |
059ec3d9 PH |
332 | { |
333 | while (p != NULL) | |
334 | { | |
335 | int c = Ustrcmp(name, p->name); | |
336 | if (c == 0) return p; | |
337 | p = (c < 0)? p->left : p->right; | |
338 | } | |
339 | return NULL; | |
340 | } | |
341 | ||
342 | ||
38a0a95f PH |
343 | |
344 | /************************************************* | |
345 | * Walk tree recursively and execute function * | |
346 | *************************************************/ | |
347 | ||
348 | /* | |
349 | Arguments: | |
350 | p root of the tree | |
351 | f function to execute for each name-value-pair | |
352 | ctx context data for f | |
353 | */ | |
354 | ||
355 | void | |
356 | tree_walk(tree_node *p, void (*f)(uschar*, uschar*, void*), void *ctx) | |
357 | { | |
358 | if (p == NULL) return; | |
359 | f(p->name, p->data.ptr, ctx); | |
360 | if (p->left != NULL) tree_walk(p->left, f, ctx); | |
361 | if (p->right != NULL) tree_walk(p->right, f, ctx); | |
362 | } | |
363 | ||
364 | ||
059ec3d9 | 365 | /* End of tree.c */ |