80aaeada |
1 | /* |
2 | * Generic reusable binary-heap maintenance code. |
3 | */ |
4 | |
5 | #include <stdlib.h> |
6 | #include <string.h> |
7 | #include "bheap.h" |
8 | |
9 | #ifdef TESTMODE |
10 | int coverage; /* bit flags for various if clauses */ |
11 | int checked_coverage; |
12 | #define COVERAGE(x) ( coverage |= (1 << (x)) ) |
13 | #else |
14 | #define COVERAGE(x) ( (void)0 ) |
15 | #endif |
16 | |
17 | struct bheap { |
18 | int nelts, maxelts; |
19 | int eltsize; |
20 | int direction; |
21 | bheap_cmpfn_t compare; |
22 | void *compare_ctx; |
23 | char *elts; |
24 | }; |
25 | |
26 | /* |
27 | * Our array is zero-based. Therefore the children of 0 are 1 and |
28 | * 2; the children of 1 are 3 and 4; of 2 are 5 and 6, and so on. |
29 | * In other words, the children of node n are 2n+1 and 2n+2, and |
30 | * the parent of node n is floor((n-1)/2). |
31 | */ |
32 | #define PARENT(n) ( ((n)-1)/2 ) |
33 | #define LCHILD(n) ( 2*(n)+1 ) |
34 | #define RCHILD(n) ( 2*(n)+2 ) |
35 | |
36 | /* |
37 | * This macro calls the compare function, and returns TRUE if the |
38 | * two elements are the wrong way up and should be swapped. |
39 | * |
40 | * It doesn't _have_ to be called on a parent and child, but its |
41 | * return value assumes that. So you could call it on any two |
42 | * elements x,y and it would return TRUE if y ought to be the |
43 | * parent of x. |
44 | */ |
45 | #define MISORDERED(bh,parent,child) \ |
46 | ( (bh)->direction * \ |
47 | (bh)->compare((bh)->compare_ctx, \ |
48 | (bh)->elts + (parent) * (bh)->eltsize, \ |
49 | (bh)->elts + (child) * (bh)->eltsize) > 0 ) |
50 | |
51 | /* |
52 | * This macro swaps two elements of the heap. |
53 | */ |
54 | #define SWAP(bh,x,y) do { \ |
55 | memcpy((bh)->elts + (bh)->maxelts * (bh)->eltsize, \ |
56 | (bh)->elts + (x) * (bh)->eltsize, (bh)->eltsize); \ |
57 | memcpy((bh)->elts + (x) * (bh)->eltsize, \ |
58 | (bh)->elts + (y) * (bh)->eltsize, (bh)->eltsize); \ |
59 | memcpy((bh)->elts + (y) * (bh)->eltsize, \ |
60 | (bh)->elts + (bh)->maxelts * (bh)->eltsize, (bh)->eltsize); \ |
61 | } while (0) |
62 | |
63 | bheap *bheap_new(int maxelts, int eltsize, int direction, |
64 | bheap_cmpfn_t compare, void *compare_ctx) |
65 | { |
66 | bheap *bh = malloc(sizeof(bheap)); |
67 | if (!bh) |
68 | return NULL; |
69 | |
70 | /* |
71 | * Allocate one extra element of space, to use for swapping |
72 | * things. |
73 | */ |
74 | bh->elts = malloc(maxelts * (eltsize+1)); |
75 | if (!bh->elts) |
76 | return NULL; |
77 | |
78 | bh->nelts = 0; |
79 | bh->maxelts = maxelts; |
80 | bh->eltsize = eltsize; |
81 | bh->direction = direction; |
82 | bh->compare = compare; |
83 | bh->compare_ctx = compare_ctx; |
84 | |
85 | return bh; |
86 | } |
87 | |
88 | void *bheap_add(bheap *bh, void *elt) |
89 | { |
90 | int i; |
91 | |
92 | if (bh->nelts >= bh->maxelts) { |
93 | COVERAGE(0); |
94 | return NULL; |
95 | } |
96 | |
97 | COVERAGE(1); |
98 | /* |
99 | * Add the element to the end of the array. |
100 | */ |
101 | memcpy(bh->elts + bh->nelts * bh->eltsize, elt, bh->eltsize); |
102 | bh->nelts++; |
103 | |
104 | /* |
105 | * Now swap it with its parent repeatedly to preserve the heap |
106 | * property. |
107 | */ |
108 | i = bh->nelts-1; |
109 | |
110 | if (i == 0) |
111 | COVERAGE(2); |
112 | |
113 | while (i > 0) { |
114 | int p = PARENT(i); |
115 | |
116 | COVERAGE(3); |
117 | |
118 | if (MISORDERED(bh, p, i)) { |
119 | COVERAGE(4); |
120 | SWAP(bh, p, i); |
121 | i = p; |
122 | } else { |
123 | COVERAGE(5); |
124 | break; /* we're done */ |
125 | } |
126 | } |
127 | |
128 | return elt; |
129 | } |
130 | |
131 | void *bheap_topmost(bheap *bh, void *elt) |
132 | { |
133 | if (bh->nelts <= 0) { |
134 | COVERAGE(6); |
135 | return NULL; |
136 | } |
137 | |
138 | COVERAGE(7); |
139 | memcpy(elt, bh->elts, bh->eltsize); |
140 | return elt; |
141 | } |
142 | |
143 | void *bheap_remove(bheap *bh, void *elt) |
144 | { |
145 | if (bh->nelts <= 0) { |
146 | COVERAGE(8); |
147 | return NULL; |
148 | } |
149 | |
150 | if (elt) |
151 | memcpy(elt, bh->elts, bh->eltsize); |
152 | |
153 | bh->nelts--; |
154 | |
155 | if (bh->nelts > 0) { |
156 | int i; |
157 | |
158 | COVERAGE(8); |
159 | /* |
160 | * Move the highest-index element of the heap into the top |
161 | * position. |
162 | */ |
163 | SWAP(bh, bh->nelts, 0); |
164 | |
165 | /* |
166 | * Now repeatedly move it down the heap by swapping it with |
167 | * the more suitable of its children. |
168 | */ |
169 | i = 0; |
170 | while (1) { |
171 | int lc, rc; |
172 | |
173 | lc = LCHILD(i); |
174 | rc = RCHILD(i); |
175 | |
176 | COVERAGE(9); |
177 | |
178 | if (lc >= bh->nelts) { |
179 | COVERAGE(10); |
180 | break; /* we've hit bottom */ |
181 | } |
182 | |
183 | if (rc >= bh->nelts) { |
184 | /* |
185 | * Special case: there is only one child to check. |
186 | */ |
187 | COVERAGE(11); |
188 | if (MISORDERED(bh, i, lc)) { |
189 | COVERAGE(12); |
190 | SWAP(bh, i, lc); |
191 | } else { |
192 | COVERAGE(13); |
193 | } |
194 | /* _Now_ we've hit bottom. */ |
195 | break; |
196 | } else { |
197 | COVERAGE(14); |
198 | /* |
199 | * The common case: there are two children and we |
200 | * must check them both. |
201 | */ |
202 | if (MISORDERED(bh, i, lc) || MISORDERED(bh, i, rc)) { |
203 | COVERAGE(15); |
204 | /* |
205 | * Pick the more appropriate child to swap with |
206 | * (i.e. the one which would want to be the |
207 | * parent if one were above the other - as one |
208 | * is about to be). |
209 | */ |
210 | if (MISORDERED(bh, lc, rc)) { |
211 | COVERAGE(16); |
212 | SWAP(bh, i, rc); |
213 | i = rc; |
214 | } else { |
215 | COVERAGE(17); |
216 | SWAP(bh, i, lc); |
217 | i = lc; |
218 | } |
219 | } else { |
220 | /* This element is in the right place; we're done. */ |
221 | COVERAGE(18); |
222 | break; |
223 | } |
224 | } |
225 | } |
226 | } else { |
227 | COVERAGE(19); |
228 | } |
229 | |
230 | return elt; |
231 | } |
232 | |
233 | int bheap_count(bheap *bh) |
234 | { |
235 | return bh->nelts; |
236 | } |
237 | |
238 | void bheap_free(bheap *bh) |
239 | { |
240 | if (bh) { |
241 | if (bh->elts) |
242 | free(bh->elts); |
243 | free(bh); |
244 | } |
245 | } |
246 | |
247 | #ifdef TESTMODE |
248 | |
249 | #include <stdio.h> |
250 | |
251 | /* we _really_ need assertions enabled, for this test */ |
252 | #undef NDEBUG |
253 | #include <assert.h> |
254 | |
255 | #define MAX 8 |
256 | |
257 | #define CHECK_COVERAGE(c, statement) do { \ |
258 | coverage &= ~ (1 << (c)); \ |
259 | statement; \ |
260 | assert(coverage & (1 << (c))); \ |
261 | checked_coverage |= (1 << (c)); \ |
262 | } while (0) |
263 | |
264 | int intcmp_ctx; |
265 | int array[MAX]; |
266 | int n; |
267 | |
268 | bheap *bh; |
269 | |
270 | int intcmp(void *vctx, const void *av, const void *bv) |
271 | { |
272 | const int *a = (const int *)av; |
273 | const int *b = (const int *)bv; |
274 | int *ctx = (int *)vctx; |
275 | |
276 | assert(ctx == &intcmp_ctx); |
277 | |
278 | if (*a < *b) |
279 | return -1; |
280 | else if (*a > *b) |
281 | return +1; |
282 | return 0; |
283 | } |
284 | |
285 | void add(int x) |
286 | { |
287 | int *ret = bheap_add(bh, &x); |
288 | |
289 | if (n >= MAX) { |
290 | assert(ret == NULL); |
291 | } else { |
292 | assert(ret == &x); |
293 | |
294 | array[n++] = x; |
295 | } |
296 | |
297 | assert(bheap_count(bh) == n); |
298 | } |
299 | |
300 | void rem(int x) |
301 | { |
302 | int out1, *ret1, out2, *ret2; |
303 | |
304 | ret1 = bheap_topmost(bh, &out1); |
305 | ret2 = bheap_remove(bh, &out2); |
306 | |
307 | if (n == 0) { |
308 | assert(x < 0); /* test the tests! */ |
309 | assert(ret1 == NULL); |
310 | assert(ret2 == NULL); |
311 | } else { |
312 | int i; |
313 | |
314 | assert(x >= 0); /* test the tests! */ |
315 | assert(ret1 == &out1); |
316 | assert(ret2 == &out2); |
317 | assert(out1 == out2); |
318 | assert(out1 == x); |
319 | |
320 | /* Now find x in _our_ array and remove it. */ |
321 | for (i = 0; i < n; i++) { |
322 | assert(array[i] >= x); |
323 | if (array[i] == x) { |
324 | int tmp; |
325 | |
326 | tmp = array[n-1]; |
327 | array[n-1] = array[i]; |
328 | array[i] = tmp; |
329 | |
330 | break; |
331 | } |
332 | } |
333 | assert(i < n); /* we expect to have found it */ |
334 | n--; |
335 | } |
336 | |
337 | assert(bheap_count(bh) == n); |
338 | } |
339 | |
340 | int main(void) |
341 | { |
342 | coverage = checked_coverage = 0; |
343 | |
344 | bh = bheap_new(MAX, sizeof(int), +1, intcmp, &intcmp_ctx); |
345 | |
346 | /* |
347 | * Various sets of adds and removes which test all the code |
348 | * paths marked with COVERAGE() statements. |
349 | */ |
350 | CHECK_COVERAGE(2, add(4)); |
351 | CHECK_COVERAGE(3, add(7)); |
352 | CHECK_COVERAGE(4, add(2)); |
353 | CHECK_COVERAGE(1, add(6)); |
354 | add(3); |
355 | add(1); |
356 | CHECK_COVERAGE(5, add(8)); |
357 | add(5); |
358 | CHECK_COVERAGE(0, add(9)); /* check the full-heap case */ |
359 | |
360 | CHECK_COVERAGE(7, rem(1)); |
361 | CHECK_COVERAGE(8, rem(2)); |
362 | CHECK_COVERAGE(9, rem(3)); |
363 | CHECK_COVERAGE(14, rem(4)); |
364 | rem(5); |
365 | rem(6); |
366 | rem(7); |
367 | CHECK_COVERAGE(19, rem(8)); |
368 | CHECK_COVERAGE(6, rem(-1)); /* and check the empty-heap case */ |
369 | CHECK_COVERAGE(8, rem(-1)); /* and check the empty-heap case */ |
370 | |
371 | add(1); |
372 | add(2); |
373 | add(3); |
374 | CHECK_COVERAGE(12, rem(1)); |
375 | rem(2); |
376 | rem(3); |
377 | |
378 | add(1); |
379 | add(3); |
380 | add(2); |
381 | CHECK_COVERAGE(13, rem(1)); |
382 | rem(2); |
383 | rem(3); |
384 | |
385 | add(1); |
386 | add(2); |
387 | add(3); |
388 | add(4); |
389 | CHECK_COVERAGE(17, rem(1)); |
390 | rem(2); |
391 | rem(3); |
392 | rem(4); |
393 | |
394 | add(1); |
395 | add(3); |
396 | add(2); |
397 | add(4); |
398 | CHECK_COVERAGE(16, rem(1)); |
399 | rem(2); |
400 | rem(3); |
401 | rem(4); |
402 | |
403 | add(1); |
404 | add(2); |
405 | add(3); |
406 | add(5); |
407 | add(6); |
408 | add(7); |
409 | add(4); |
410 | CHECK_COVERAGE(18, rem(1)); |
411 | CHECK_COVERAGE(15, rem(2)); |
412 | rem(3); |
413 | CHECK_COVERAGE(10, rem(4)); |
414 | CHECK_COVERAGE(11, rem(5)); |
415 | rem(6); |
416 | rem(7); |
417 | |
418 | /* |
419 | * See what happens with compare equality. |
420 | */ |
421 | add(3); |
422 | add(3); |
423 | add(3); |
424 | add(3); |
425 | add(3); |
426 | add(3); |
427 | add(3); |
428 | add(3); |
429 | rem(3); |
430 | rem(3); |
431 | rem(3); |
432 | rem(3); |
433 | rem(3); |
434 | rem(3); |
435 | rem(3); |
436 | rem(3); |
437 | |
438 | add(5); |
439 | add(4); |
440 | add(7); |
441 | add(4); |
442 | add(1); |
443 | add(4); |
444 | add(3); |
445 | rem(1); |
446 | rem(3); |
447 | rem(4); |
448 | rem(4); |
449 | rem(4); |
450 | rem(5); |
451 | rem(7); |
452 | |
453 | /* |
454 | * Interleave some adds and removes, turning the heap into a |
455 | * real priority queue rather than a glorified sorter. |
456 | * |
457 | * We add the digits of pi in order, and keep the heap size |
458 | * capped at 5 by extracting one before adding the next. |
459 | * |
460 | * Python code that generates this test sequence: |
461 | |
462 | python -c ' |
463 | list=[] |
464 | for c in "314159265358979323846264338327950288": |
465 | c = int(c) |
466 | if len(list) >= 5: |
467 | list.sort() |
468 | d = list[0] |
469 | del list[0] |
470 | print (" rem(%d); /"+"* %s *"+"/") % (d, repr(list)) |
471 | list.append(c) |
472 | list.sort() |
473 | print (" add(%d); /"+"* %s *"+"/") % (c, repr(list)) |
474 | while len(list) > 0: |
475 | list.sort() |
476 | d = list[0] |
477 | del list[0] |
478 | print (" rem(%d); /"+"* %s *"+"/") % (d, repr(list)) |
479 | print " rem(-1);" |
480 | ' |
481 | |
482 | */ |
483 | add(3); /* [3] */ |
484 | add(1); /* [1, 3] */ |
485 | add(4); /* [1, 3, 4] */ |
486 | add(1); /* [1, 1, 3, 4] */ |
487 | add(5); /* [1, 1, 3, 4, 5] */ |
488 | rem(1); /* [1, 3, 4, 5] */ |
489 | add(9); /* [1, 3, 4, 5, 9] */ |
490 | rem(1); /* [3, 4, 5, 9] */ |
491 | add(2); /* [2, 3, 4, 5, 9] */ |
492 | rem(2); /* [3, 4, 5, 9] */ |
493 | add(6); /* [3, 4, 5, 6, 9] */ |
494 | rem(3); /* [4, 5, 6, 9] */ |
495 | add(5); /* [4, 5, 5, 6, 9] */ |
496 | rem(4); /* [5, 5, 6, 9] */ |
497 | add(3); /* [3, 5, 5, 6, 9] */ |
498 | rem(3); /* [5, 5, 6, 9] */ |
499 | add(5); /* [5, 5, 5, 6, 9] */ |
500 | rem(5); /* [5, 5, 6, 9] */ |
501 | add(8); /* [5, 5, 6, 8, 9] */ |
502 | rem(5); /* [5, 6, 8, 9] */ |
503 | add(9); /* [5, 6, 8, 9, 9] */ |
504 | rem(5); /* [6, 8, 9, 9] */ |
505 | add(7); /* [6, 7, 8, 9, 9] */ |
506 | rem(6); /* [7, 8, 9, 9] */ |
507 | add(9); /* [7, 8, 9, 9, 9] */ |
508 | rem(7); /* [8, 9, 9, 9] */ |
509 | add(3); /* [3, 8, 9, 9, 9] */ |
510 | rem(3); /* [8, 9, 9, 9] */ |
511 | add(2); /* [2, 8, 9, 9, 9] */ |
512 | rem(2); /* [8, 9, 9, 9] */ |
513 | add(3); /* [3, 8, 9, 9, 9] */ |
514 | rem(3); /* [8, 9, 9, 9] */ |
515 | add(8); /* [8, 8, 9, 9, 9] */ |
516 | rem(8); /* [8, 9, 9, 9] */ |
517 | add(4); /* [4, 8, 9, 9, 9] */ |
518 | rem(4); /* [8, 9, 9, 9] */ |
519 | add(6); /* [6, 8, 9, 9, 9] */ |
520 | rem(6); /* [8, 9, 9, 9] */ |
521 | add(2); /* [2, 8, 9, 9, 9] */ |
522 | rem(2); /* [8, 9, 9, 9] */ |
523 | add(6); /* [6, 8, 9, 9, 9] */ |
524 | rem(6); /* [8, 9, 9, 9] */ |
525 | add(4); /* [4, 8, 9, 9, 9] */ |
526 | rem(4); /* [8, 9, 9, 9] */ |
527 | add(3); /* [3, 8, 9, 9, 9] */ |
528 | rem(3); /* [8, 9, 9, 9] */ |
529 | add(3); /* [3, 8, 9, 9, 9] */ |
530 | rem(3); /* [8, 9, 9, 9] */ |
531 | add(8); /* [8, 8, 9, 9, 9] */ |
532 | rem(8); /* [8, 9, 9, 9] */ |
533 | add(3); /* [3, 8, 9, 9, 9] */ |
534 | rem(3); /* [8, 9, 9, 9] */ |
535 | add(2); /* [2, 8, 9, 9, 9] */ |
536 | rem(2); /* [8, 9, 9, 9] */ |
537 | add(7); /* [7, 8, 9, 9, 9] */ |
538 | rem(7); /* [8, 9, 9, 9] */ |
539 | add(9); /* [8, 9, 9, 9, 9] */ |
540 | rem(8); /* [9, 9, 9, 9] */ |
541 | add(5); /* [5, 9, 9, 9, 9] */ |
542 | rem(5); /* [9, 9, 9, 9] */ |
543 | add(0); /* [0, 9, 9, 9, 9] */ |
544 | rem(0); /* [9, 9, 9, 9] */ |
545 | add(2); /* [2, 9, 9, 9, 9] */ |
546 | rem(2); /* [9, 9, 9, 9] */ |
547 | add(8); /* [8, 9, 9, 9, 9] */ |
548 | rem(8); /* [9, 9, 9, 9] */ |
549 | add(8); /* [8, 9, 9, 9, 9] */ |
550 | rem(8); /* [9, 9, 9, 9] */ |
551 | rem(9); /* [9, 9, 9] */ |
552 | rem(9); /* [9, 9] */ |
553 | rem(9); /* [9] */ |
554 | rem(9); /* [] */ |
555 | rem(-1); |
556 | |
557 | bheap_free(bh); |
558 | |
559 | { |
560 | int i; |
561 | |
562 | for (i = 0; i < 20; i++) { |
563 | if (!(coverage & (1 << i))) |
564 | printf("coverage is missing %d\n", i); |
565 | else if (!(checked_coverage & (1 << i))) |
566 | printf("checked_coverage is missing %d\n", i); |
567 | } |
568 | } |
569 | |
570 | printf("finished testing, no assertions failed\n"); |
571 | |
572 | return 0; |
573 | } |
574 | |
575 | #endif |