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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 | ||
165acdd1 | 15 | #ifndef MACRO_PREDEF |
059ec3d9 PH |
16 | |
17 | ||
18 | /************************************************* | |
19 | * Add entry to non-recipients tree * | |
20 | *************************************************/ | |
21 | ||
22 | /* Duplicates are just discarded. | |
23 | ||
24 | Arguments: | |
25 | s string to add | |
26 | ||
27 | Returns: nothing | |
28 | */ | |
29 | ||
30 | void | |
31 | tree_add_nonrecipient(uschar *s) | |
32 | { | |
33 | tree_node *node = store_get(sizeof(tree_node) + Ustrlen(s)); | |
34 | Ustrcpy(node->name, s); | |
35 | node->data.ptr = NULL; | |
36 | if (!tree_insertnode(&tree_nonrecipients, node)) store_reset(node); | |
37 | } | |
38 | ||
39 | ||
40 | ||
41 | /************************************************* | |
42 | * Add entry to duplicates tree * | |
43 | *************************************************/ | |
44 | ||
45 | /* Duplicates are just discarded. | |
46 | ||
47 | Argument: | |
48 | s string to add | |
49 | addr the address is is a duplicate of | |
50 | ||
51 | Returns: nothing | |
52 | */ | |
53 | ||
54 | void | |
55 | tree_add_duplicate(uschar *s, address_item *addr) | |
56 | { | |
57 | tree_node *node = store_get(sizeof(tree_node) + Ustrlen(s)); | |
58 | Ustrcpy(node->name, s); | |
59 | node->data.ptr = addr; | |
60 | if (!tree_insertnode(&tree_duplicates, node)) store_reset(node); | |
61 | } | |
62 | ||
63 | ||
64 | ||
65 | /************************************************* | |
66 | * Add entry to unusable addresses tree * | |
67 | *************************************************/ | |
68 | ||
69 | /* Duplicates are simply discarded. | |
70 | ||
71 | Argument: the host item | |
72 | Returns: nothing | |
73 | */ | |
74 | ||
75 | void | |
76 | tree_add_unusable(host_item *h) | |
77 | { | |
78 | tree_node *node; | |
79 | uschar s[256]; | |
80 | sprintf(CS s, "T:%.200s:%s", h->name, h->address); | |
81 | node = store_get(sizeof(tree_node) + Ustrlen(s)); | |
82 | Ustrcpy(node->name, s); | |
83 | node->data.val = h->why; | |
84 | if (h->status == hstatus_unusable_expired) node->data.val += 256; | |
85 | if (!tree_insertnode(&tree_unusable, node)) store_reset(node); | |
86 | } | |
87 | ||
88 | ||
89 | ||
90 | /************************************************* | |
91 | * Write a tree in re-readable form * | |
92 | *************************************************/ | |
93 | ||
94 | /* This function writes out a tree in a form in which it can | |
95 | easily be re-read. It is used for writing out the non-recipients | |
96 | tree onto the spool, for retrieval at the next retry time. | |
97 | ||
98 | The format is as follows: | |
99 | ||
100 | . If the tree is empty, write one line containing XX. | |
101 | ||
102 | . Otherwise, each node is written, preceded by two letters | |
103 | (Y/N) indicating whether it has left or right children. | |
104 | ||
105 | . The left subtree (if any) then follows, then the right subtree. | |
106 | ||
107 | First, there's an internal recursive subroutine. | |
108 | ||
109 | Arguments: | |
110 | p current node | |
111 | f FILE to write to | |
112 | ||
113 | Returns: nothing | |
114 | */ | |
115 | ||
116 | static void | |
117 | write_tree(tree_node *p, FILE *f) | |
118 | { | |
165acdd1 JH |
119 | fprintf(f, "%c%c %s\n", p->left ? 'Y':'N', p->right ? 'Y':'N', p->name); |
120 | if (p->left) write_tree(p->left, f); | |
121 | if (p->right) write_tree(p->right, f); | |
059ec3d9 PH |
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 | { | |
165acdd1 | 129 | if (!p) |
059ec3d9 PH |
130 | { |
131 | fprintf(f, "XX\n"); | |
132 | return; | |
133 | } | |
134 | write_tree(p, f); | |
135 | } | |
136 | ||
137 | ||
165acdd1 | 138 | #endif |
059ec3d9 PH |
139 | |
140 | ||
141 | ||
142 | /*********************************************************** | |
143 | * Binary Balanced Tree Management Routines * | |
144 | ***********************************************************/ | |
145 | ||
146 | /* This set of routines maintains a balanced binary tree using | |
147 | the algorithm given in Knuth Vol 3 page 455. | |
148 | ||
149 | The routines make use of uschar * pointers as byte pointers, | |
150 | so as to be able to do arithmetic on them, since ANSI Standard | |
151 | C does not permit additions and subtractions on void pointers. */ | |
152 | ||
153 | ||
154 | /************************************************* | |
155 | * Flags and Parameters * | |
156 | *************************************************/ | |
157 | ||
158 | #define tree_lbal 1 /* left subtree is longer */ | |
159 | #define tree_rbal 2 /* right subtree is longer */ | |
160 | #define tree_bmask 3 /* mask for flipping bits */ | |
161 | ||
162 | ||
163 | /************************************************* | |
164 | * Insert a new node into a tree * | |
165 | *************************************************/ | |
166 | ||
167 | /* The node->name field must (obviously) be set, but the other | |
168 | fields need not be initialized. | |
169 | ||
170 | Arguments: | |
171 | treebase pointer to the root of the tree | |
172 | node the note to insert, with name field set | |
173 | ||
174 | Returns: TRUE if node inserted; FALSE if not (duplicate) | |
175 | */ | |
176 | ||
177 | int | |
178 | tree_insertnode(tree_node **treebase, tree_node *node) | |
179 | { | |
180 | tree_node *p = *treebase; | |
181 | tree_node **q, *r, *s, **t; | |
182 | int a; | |
183 | ||
184 | node->left = node->right = NULL; | |
185 | node->balance = 0; | |
186 | ||
187 | /* Deal with an empty tree */ | |
188 | ||
165acdd1 | 189 | if (!p) |
059ec3d9 PH |
190 | { |
191 | *treebase = node; | |
192 | return TRUE; | |
193 | } | |
194 | ||
195 | /* The tree is not empty. While finding the insertion point, | |
196 | q points to the pointer to p, and t points to the pointer to | |
197 | the potential re-balancing point. */ | |
198 | ||
199 | q = treebase; | |
200 | t = q; | |
201 | ||
202 | /* Loop to search tree for place to insert new node */ | |
203 | ||
204 | for (;;) | |
205 | { | |
206 | int c = Ustrcmp(node->name, p->name); | |
207 | if (c == 0) return FALSE; /* Duplicate node encountered */ | |
208 | ||
209 | /* Deal with climbing down the tree, exiting from the loop | |
210 | when we reach a leaf. */ | |
211 | ||
165acdd1 | 212 | q = c > 0 ? &p->right : &p->left; |
059ec3d9 | 213 | p = *q; |
165acdd1 | 214 | if (!p) break; |
059ec3d9 PH |
215 | |
216 | /* Save the address of the pointer to the last node en route | |
217 | which has a non-zero balance factor. */ | |
218 | ||
219 | if (p->balance != 0) t = q; | |
220 | } | |
221 | ||
222 | /* When the above loop completes, q points to the pointer to NULL; | |
223 | that is the place at which the new node must be inserted. */ | |
224 | ||
225 | *q = node; | |
226 | ||
227 | /* Set up s as the potential re-balancing point, and r as the | |
228 | next node after it along the route. */ | |
229 | ||
230 | s = *t; | |
165acdd1 | 231 | r = Ustrcmp(node->name, s->name) > 0 ? s->right : s->left; |
059ec3d9 PH |
232 | |
233 | /* Adjust balance factors along the route from s to node. */ | |
234 | ||
235 | p = r; | |
236 | ||
237 | while (p != node) | |
059ec3d9 PH |
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 | } | |
059ec3d9 PH |
248 | |
249 | /* Now the World-Famous Balancing Act */ | |
250 | ||
165acdd1 | 251 | a = Ustrcmp(node->name, s->name) < 0 ? tree_lbal : tree_rbal; |
059ec3d9 | 252 | |
165acdd1 JH |
253 | if (s->balance == 0) |
254 | s->balance = (uschar)a; /* The tree has grown higher */ | |
255 | else if (s->balance != (uschar)a) | |
256 | s->balance = 0; /* It's become more balanced */ | |
257 | else /* It's got out of balance */ | |
059ec3d9 PH |
258 | { |
259 | /* Perform a single rotation */ | |
260 | ||
261 | if (r->balance == (uschar)a) | |
262 | { | |
263 | p = r; | |
264 | if (a == tree_rbal) | |
265 | { | |
266 | s->right = r->left; | |
267 | r->left = s; | |
268 | } | |
269 | else | |
270 | { | |
271 | s->left = r->right; | |
272 | r->right = s; | |
273 | } | |
274 | s->balance = 0; | |
275 | r->balance = 0; | |
276 | } | |
277 | ||
278 | /* Perform a double rotation There was an occasion when the balancing | |
279 | factors were screwed up by a bug in the code that reads a tree from | |
280 | the spool. In case this ever happens again, check for changing p to NULL | |
281 | and don't do it. It is better to have an unbalanced tree than a crash. */ | |
282 | ||
283 | else | |
284 | { | |
285 | if (a == tree_rbal) | |
286 | { | |
165acdd1 | 287 | if (!r->left) return TRUE; /* Bail out if tree corrupt */ |
059ec3d9 PH |
288 | p = r->left; |
289 | r->left = p->right; | |
290 | p->right = r; | |
291 | s->right = p->left; | |
292 | p->left = s; | |
293 | } | |
294 | else | |
295 | { | |
165acdd1 | 296 | if (!r->right) return TRUE; /* Bail out if tree corrupt */ |
059ec3d9 PH |
297 | p = r->right; |
298 | r->right = p->left; | |
299 | p->left = r; | |
300 | s->left = p->right; | |
301 | p->right = s; | |
302 | } | |
303 | ||
165acdd1 JH |
304 | s->balance = p->balance == (uschar)a ? (uschar)(a^tree_bmask) : 0; |
305 | r->balance = p->balance == (uschar)(a^tree_bmask) ? (uschar)a : 0; | |
059ec3d9 PH |
306 | p->balance = 0; |
307 | } | |
308 | ||
309 | /* Finishing touch */ | |
310 | ||
311 | *t = p; | |
312 | } | |
313 | ||
314 | return TRUE; /* Successful insertion */ | |
315 | } | |
316 | ||
317 | ||
318 | ||
319 | /************************************************* | |
320 | * Search tree for node by name * | |
321 | *************************************************/ | |
322 | ||
323 | /* | |
324 | Arguments: | |
325 | p root of tree | |
326 | name key to search for | |
327 | ||
328 | Returns: pointer to node, or NULL if not found | |
329 | */ | |
330 | ||
331 | tree_node * | |
55414b25 | 332 | tree_search(tree_node *p, const uschar *name) |
059ec3d9 | 333 | { |
165acdd1 JH |
334 | int c; |
335 | for ( ; p; p = c < 0 ? p->left : p->right) | |
336 | if ((c = Ustrcmp(name, p->name)) == 0) | |
337 | return p; | |
059ec3d9 PH |
338 | return NULL; |
339 | } | |
340 | ||
341 | ||
165acdd1 | 342 | #ifndef MACRO_PREDEF |
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 | { | |
2c0f3ea1 | 358 | if (!p) return; |
38a0a95f | 359 | f(p->name, p->data.ptr, ctx); |
2c0f3ea1 JH |
360 | tree_walk(p->left, f, ctx); |
361 | tree_walk(p->right, f, ctx); | |
38a0a95f PH |
362 | } |
363 | ||
165acdd1 | 364 | #endif |
38a0a95f | 365 | |
059ec3d9 | 366 | /* End of tree.c */ |