Raw
1 /*
2 * LibXDiff by Davide Libenzi ( File Differential Library )
3 * Copyright (C) 2003 Davide Libenzi
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, see
17 * <http://www.gnu.org/licenses/>.
18 *
19 * Davide Libenzi <davidel@xmailserver.org>
20 *
21 */
22
23 #include "xinclude.h"
24
25 static size_t get_hash(xdfile_t *xdf, long index)
26 {
27 return xdf->recs[xdf->reference_index[index]].minimal_perfect_hash;
28 }
29
30 #define XDL_MAX_COST_MIN 256
31 #define XDL_HEUR_MIN_COST 256
32 #define XDL_LINE_MAX (long)((1UL << (CHAR_BIT * sizeof(long) - 1)) - 1)
33 #define XDL_SNAKE_CNT 20
34 #define XDL_K_HEUR 4
35
36 typedef struct s_xdpsplit {
37 long i1, i2;
38 int min_lo, min_hi;
39 } xdpsplit_t;
40
41 /*
42 * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
43 * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
44 * the forward diagonal starting from (off1, off2) and the backward diagonal
45 * starting from (lim1, lim2). If the K values on the same diagonal crosses
46 * returns the furthest point of reach. We might encounter expensive edge cases
47 * using this algorithm, so a little bit of heuristic is needed to cut the
48 * search and to return a suboptimal point.
49 */
50 static long xdl_split(xdfile_t *xdf1, long off1, long lim1,
51 xdfile_t *xdf2, long off2, long lim2,
52 long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
53 xdalgoenv_t *xenv) {
54 long dmin = off1 - lim2, dmax = lim1 - off2;
55 long fmid = off1 - off2, bmid = lim1 - lim2;
56 long odd = (fmid - bmid) & 1;
57 long fmin = fmid, fmax = fmid;
58 long bmin = bmid, bmax = bmid;
59 long ec, d, i1, i2, prev1, best, dd, v, k;
60
61 /*
62 * Set initial diagonal values for both forward and backward path.
63 */
64 kvdf[fmid] = off1;
65 kvdb[bmid] = lim1;
66
67 for (ec = 1;; ec++) {
68 int got_snake = 0;
69
70 /*
71 * We need to extend the diagonal "domain" by one. If the next
72 * values exits the box boundaries we need to change it in the
73 * opposite direction because (max - min) must be a power of
74 * two.
75 *
76 * Also we initialize the external K value to -1 so that we can
77 * avoid extra conditions in the check inside the core loop.
78 */
79 if (fmin > dmin)
80 kvdf[--fmin - 1] = -1;
81 else
82 ++fmin;
83 if (fmax < dmax)
84 kvdf[++fmax + 1] = -1;
85 else
86 --fmax;
87
88 for (d = fmax; d >= fmin; d -= 2) {
89 if (kvdf[d - 1] >= kvdf[d + 1])
90 i1 = kvdf[d - 1] + 1;
91 else
92 i1 = kvdf[d + 1];
93 prev1 = i1;
94 i2 = i1 - d;
95 for (; i1 < lim1 && i2 < lim2 && get_hash(xdf1, i1) == get_hash(xdf2, i2); i1++, i2++);
96 if (i1 - prev1 > xenv->snake_cnt)
97 got_snake = 1;
98 kvdf[d] = i1;
99 if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
100 spl->i1 = i1;
101 spl->i2 = i2;
102 spl->min_lo = spl->min_hi = 1;
103 return ec;
104 }
105 }
106
107 /*
108 * We need to extend the diagonal "domain" by one. If the next
109 * values exits the box boundaries we need to change it in the
110 * opposite direction because (max - min) must be a power of
111 * two.
112 *
113 * Also we initialize the external K value to -1 so that we can
114 * avoid extra conditions in the check inside the core loop.
115 */
116 if (bmin > dmin)
117 kvdb[--bmin - 1] = XDL_LINE_MAX;
118 else
119 ++bmin;
120 if (bmax < dmax)
121 kvdb[++bmax + 1] = XDL_LINE_MAX;
122 else
123 --bmax;
124
125 for (d = bmax; d >= bmin; d -= 2) {
126 if (kvdb[d - 1] < kvdb[d + 1])
127 i1 = kvdb[d - 1];
128 else
129 i1 = kvdb[d + 1] - 1;
130 prev1 = i1;
131 i2 = i1 - d;
132 for (; i1 > off1 && i2 > off2 && get_hash(xdf1, i1 - 1) == get_hash(xdf2, i2 - 1); i1--, i2--);
133 if (prev1 - i1 > xenv->snake_cnt)
134 got_snake = 1;
135 kvdb[d] = i1;
136 if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
137 spl->i1 = i1;
138 spl->i2 = i2;
139 spl->min_lo = spl->min_hi = 1;
140 return ec;
141 }
142 }
143
144 if (need_min)
145 continue;
146
147 /*
148 * If the edit cost is above the heuristic trigger and if
149 * we got a good snake, we sample current diagonals to see
150 * if some of them have reached an "interesting" path. Our
151 * measure is a function of the distance from the diagonal
152 * corner (i1 + i2) penalized with the distance from the
153 * mid diagonal itself. If this value is above the current
154 * edit cost times a magic factor (XDL_K_HEUR) we consider
155 * it interesting.
156 */
157 if (got_snake && ec > xenv->heur_min) {
158 for (best = 0, d = fmax; d >= fmin; d -= 2) {
159 dd = d > fmid ? d - fmid: fmid - d;
160 i1 = kvdf[d];
161 i2 = i1 - d;
162 v = (i1 - off1) + (i2 - off2) - dd;
163
164 if (v > XDL_K_HEUR * ec && v > best &&
165 off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
166 off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
167 for (k = 1; get_hash(xdf1, i1 - k) == get_hash(xdf2, i2 - k); k++)
168 if (k == xenv->snake_cnt) {
169 best = v;
170 spl->i1 = i1;
171 spl->i2 = i2;
172 break;
173 }
174 }
175 }
176 if (best > 0) {
177 spl->min_lo = 1;
178 spl->min_hi = 0;
179 return ec;
180 }
181
182 for (best = 0, d = bmax; d >= bmin; d -= 2) {
183 dd = d > bmid ? d - bmid: bmid - d;
184 i1 = kvdb[d];
185 i2 = i1 - d;
186 v = (lim1 - i1) + (lim2 - i2) - dd;
187
188 if (v > XDL_K_HEUR * ec && v > best &&
189 off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
190 off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
191 for (k = 0; get_hash(xdf1, i1 + k) == get_hash(xdf2, i2 + k); k++)
192 if (k == xenv->snake_cnt - 1) {
193 best = v;
194 spl->i1 = i1;
195 spl->i2 = i2;
196 break;
197 }
198 }
199 }
200 if (best > 0) {
201 spl->min_lo = 0;
202 spl->min_hi = 1;
203 return ec;
204 }
205 }
206
207 /*
208 * Enough is enough. We spent too much time here and now we
209 * collect the furthest reaching path using the (i1 + i2)
210 * measure.
211 */
212 if (ec >= xenv->mxcost) {
213 long fbest, fbest1, bbest, bbest1;
214
215 fbest = fbest1 = -1;
216 for (d = fmax; d >= fmin; d -= 2) {
217 i1 = XDL_MIN(kvdf[d], lim1);
218 i2 = i1 - d;
219 if (lim2 < i2) {
220 i1 = lim2 + d;
221 i2 = lim2;
222 }
223 if (fbest < i1 + i2) {
224 fbest = i1 + i2;
225 fbest1 = i1;
226 }
227 }
228
229 bbest = bbest1 = XDL_LINE_MAX;
230 for (d = bmax; d >= bmin; d -= 2) {
231 i1 = XDL_MAX(off1, kvdb[d]);
232 i2 = i1 - d;
233 if (i2 < off2) {
234 i1 = off2 + d;
235 i2 = off2;
236 }
237 if (i1 + i2 < bbest) {
238 bbest = i1 + i2;
239 bbest1 = i1;
240 }
241 }
242
243 if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
244 spl->i1 = fbest1;
245 spl->i2 = fbest - fbest1;
246 spl->min_lo = 1;
247 spl->min_hi = 0;
248 } else {
249 spl->i1 = bbest1;
250 spl->i2 = bbest - bbest1;
251 spl->min_lo = 0;
252 spl->min_hi = 1;
253 }
254 return ec;
255 }
256 }
257 }
258
259
260 /*
261 * Rule: "Divide et Impera" (divide & conquer). Recursively split the box in
262 * sub-boxes by calling the box splitting function. Note that the real job
263 * (marking changed lines) is done in the two boundary reaching checks.
264 */
265 int xdl_recs_cmp(xdfile_t *xdf1, long off1, long lim1,
266 xdfile_t *xdf2, long off2, long lim2,
267 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
268
269 /*
270 * Shrink the box by walking through each diagonal snake (SW and NE).
271 */
272 for (; off1 < lim1 && off2 < lim2 && get_hash(xdf1, off1) == get_hash(xdf2, off2); off1++, off2++);
273 for (; off1 < lim1 && off2 < lim2 && get_hash(xdf1, lim1 - 1) == get_hash(xdf2, lim2 - 1); lim1--, lim2--);
274
275 /*
276 * If one dimension is empty, then all records on the other one must
277 * be obviously changed.
278 */
279 if (off1 == lim1) {
280 for (; off2 < lim2; off2++)
281 xdf2->changed[xdf2->reference_index[off2]] = true;
282 } else if (off2 == lim2) {
283 for (; off1 < lim1; off1++)
284 xdf1->changed[xdf1->reference_index[off1]] = true;
285 } else {
286 xdpsplit_t spl;
287 spl.i1 = spl.i2 = 0;
288
289 /*
290 * Divide ...
291 */
292 if (xdl_split(xdf1, off1, lim1, xdf2, off2, lim2, kvdf, kvdb,
293 need_min, &spl, xenv) < 0) {
294
295 return -1;
296 }
297
298 /*
299 * ... et Impera.
300 */
301 if (xdl_recs_cmp(xdf1, off1, spl.i1, xdf2, off2, spl.i2,
302 kvdf, kvdb, spl.min_lo, xenv) < 0 ||
303 xdl_recs_cmp(xdf1, spl.i1, lim1, xdf2, spl.i2, lim2,
304 kvdf, kvdb, spl.min_hi, xenv) < 0) {
305
306 return -1;
307 }
308 }
309
310 return 0;
311 }
312
313
314 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
315 xdfenv_t *xe) {
316 long ndiags;
317 long *kvd, *kvdf, *kvdb;
318 xdalgoenv_t xenv;
319 int res;
320
321 if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0)
322 return -1;
323
324 if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF) {
325 res = xdl_do_patience_diff(xpp, xe);
326 goto out;
327 }
328
329 if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF) {
330 res = xdl_do_histogram_diff(xpp, xe);
331 goto out;
332 }
333
334 /*
335 * Allocate and setup K vectors to be used by the differential
336 * algorithm.
337 *
338 * One is to store the forward path and one to store the backward path.
339 */
340 ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
341 if (!XDL_ALLOC_ARRAY(kvd, 2 * ndiags + 2)) {
342
343 xdl_free_env(xe);
344 return -1;
345 }
346 kvdf = kvd;
347 kvdb = kvdf + ndiags;
348 kvdf += xe->xdf2.nreff + 1;
349 kvdb += xe->xdf2.nreff + 1;
350
351 xenv.mxcost = (long)xdl_bogosqrt((uint64_t)ndiags);
352 if (xenv.mxcost < XDL_MAX_COST_MIN)
353 xenv.mxcost = XDL_MAX_COST_MIN;
354 xenv.snake_cnt = XDL_SNAKE_CNT;
355 xenv.heur_min = XDL_HEUR_MIN_COST;
356
357 res = xdl_recs_cmp(&xe->xdf1, 0, xe->xdf1.nreff, &xe->xdf2, 0, xe->xdf2.nreff,
358 kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0,
359 &xenv);
360 xdl_free(kvd);
361 out:
362 if (res < 0)
363 xdl_free_env(xe);
364
365 return res;
366 }
367
368
369 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
370 xdchange_t *xch;
371
372 if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
373 return NULL;
374
375 xch->next = xscr;
376 xch->i1 = i1;
377 xch->i2 = i2;
378 xch->chg1 = chg1;
379 xch->chg2 = chg2;
380 xch->ignore = 0;
381
382 return xch;
383 }
384
385
386 static int recs_match(xrecord_t *rec1, xrecord_t *rec2)
387 {
388 return rec1->minimal_perfect_hash == rec2->minimal_perfect_hash;
389 }
390
391 /*
392 * If a line is indented more than this, get_indent() just returns this value.
393 * This avoids having to do absurd amounts of work for data that are not
394 * human-readable text, and also ensures that the output of get_indent fits
395 * within an int.
396 */
397 #define MAX_INDENT 200
398
399 /*
400 * Return the amount of indentation of the specified line, treating TAB as 8
401 * columns. Return -1 if line is empty or contains only whitespace. Clamp the
402 * output value at MAX_INDENT.
403 */
404 static int get_indent(xrecord_t *rec)
405 {
406 int ret = 0;
407
408 for (size_t i = 0; i < rec->size; i++) {
409 char c = (char) rec->ptr[i];
410
411 if (!XDL_ISSPACE(c))
412 return ret;
413 else if (c == ' ')
414 ret += 1;
415 else if (c == '\t')
416 ret += 8 - ret % 8;
417 /* ignore other whitespace characters */
418
419 if (ret >= MAX_INDENT)
420 return MAX_INDENT;
421 }
422
423 /* The line contains only whitespace. */
424 return -1;
425 }
426
427 /*
428 * If more than this number of consecutive blank rows are found, just return
429 * this value. This avoids requiring O(N^2) work for pathological cases, and
430 * also ensures that the output of score_split fits in an int.
431 */
432 #define MAX_BLANKS 20
433
434 /* Characteristics measured about a hypothetical split position. */
435 struct split_measurement {
436 /*
437 * Is the split at the end of the file (aside from any blank lines)?
438 */
439 int end_of_file;
440
441 /*
442 * How much is the line immediately following the split indented (or -1
443 * if the line is blank):
444 */
445 int indent;
446
447 /*
448 * How many consecutive lines above the split are blank?
449 */
450 int pre_blank;
451
452 /*
453 * How much is the nearest non-blank line above the split indented (or
454 * -1 if there is no such line)?
455 */
456 int pre_indent;
457
458 /*
459 * How many lines after the line following the split are blank?
460 */
461 int post_blank;
462
463 /*
464 * How much is the nearest non-blank line after the line following the
465 * split indented (or -1 if there is no such line)?
466 */
467 int post_indent;
468 };
469
470 struct split_score {
471 /* The effective indent of this split (smaller is preferred). */
472 int effective_indent;
473
474 /* Penalty for this split (smaller is preferred). */
475 int penalty;
476 };
477
478 /*
479 * Fill m with information about a hypothetical split of xdf above line split.
480 */
481 static void measure_split(const xdfile_t *xdf, long split,
482 struct split_measurement *m)
483 {
484 long i;
485
486 if (split >= (long)xdf->nrec) {
487 m->end_of_file = 1;
488 m->indent = -1;
489 } else {
490 m->end_of_file = 0;
491 m->indent = get_indent(&xdf->recs[split]);
492 }
493
494 m->pre_blank = 0;
495 m->pre_indent = -1;
496 for (i = split - 1; i >= 0; i--) {
497 m->pre_indent = get_indent(&xdf->recs[i]);
498 if (m->pre_indent != -1)
499 break;
500 m->pre_blank += 1;
501 if (m->pre_blank == MAX_BLANKS) {
502 m->pre_indent = 0;
503 break;
504 }
505 }
506
507 m->post_blank = 0;
508 m->post_indent = -1;
509 for (i = split + 1; i < (long)xdf->nrec; i++) {
510 m->post_indent = get_indent(&xdf->recs[i]);
511 if (m->post_indent != -1)
512 break;
513 m->post_blank += 1;
514 if (m->post_blank == MAX_BLANKS) {
515 m->post_indent = 0;
516 break;
517 }
518 }
519 }
520
521 /*
522 * The empirically-determined weight factors used by score_split() below.
523 * Larger values means that the position is a less favorable place to split.
524 *
525 * Note that scores are only ever compared against each other, so multiplying
526 * all of these weight/penalty values by the same factor wouldn't change the
527 * heuristic's behavior. Still, we need to set that arbitrary scale *somehow*.
528 * In practice, these numbers are chosen to be large enough that they can be
529 * adjusted relative to each other with sufficient precision despite using
530 * integer math.
531 */
532
533 /* Penalty if there are no non-blank lines before the split */
534 #define START_OF_FILE_PENALTY 1
535
536 /* Penalty if there are no non-blank lines after the split */
537 #define END_OF_FILE_PENALTY 21
538
539 /* Multiplier for the number of blank lines around the split */
540 #define TOTAL_BLANK_WEIGHT (-30)
541
542 /* Multiplier for the number of blank lines after the split */
543 #define POST_BLANK_WEIGHT 6
544
545 /*
546 * Penalties applied if the line is indented more than its predecessor
547 */
548 #define RELATIVE_INDENT_PENALTY (-4)
549 #define RELATIVE_INDENT_WITH_BLANK_PENALTY 10
550
551 /*
552 * Penalties applied if the line is indented less than both its predecessor and
553 * its successor
554 */
555 #define RELATIVE_OUTDENT_PENALTY 24
556 #define RELATIVE_OUTDENT_WITH_BLANK_PENALTY 17
557
558 /*
559 * Penalties applied if the line is indented less than its predecessor but not
560 * less than its successor
561 */
562 #define RELATIVE_DEDENT_PENALTY 23
563 #define RELATIVE_DEDENT_WITH_BLANK_PENALTY 17
564
565 /*
566 * We only consider whether the sum of the effective indents for splits are
567 * less than (-1), equal to (0), or greater than (+1) each other. The resulting
568 * value is multiplied by the following weight and combined with the penalty to
569 * determine the better of two scores.
570 */
571 #define INDENT_WEIGHT 60
572
573 /*
574 * How far do we slide a hunk at most?
575 */
576 #define INDENT_HEURISTIC_MAX_SLIDING 100
577
578 /*
579 * Compute a badness score for the hypothetical split whose measurements are
580 * stored in m. The weight factors were determined empirically using the tools
581 * and corpus described in
582 *
583 * https://github.com/mhagger/diff-slider-tools
584 *
585 * Also see that project if you want to improve the weights based on, for
586 * example, a larger or more diverse corpus.
587 */
588 static void score_add_split(const struct split_measurement *m, struct split_score *s)
589 {
590 /*
591 * A place to accumulate penalty factors (positive makes this index more
592 * favored):
593 */
594 int post_blank, total_blank, indent, any_blanks;
595
596 if (m->pre_indent == -1 && m->pre_blank == 0)
597 s->penalty += START_OF_FILE_PENALTY;
598
599 if (m->end_of_file)
600 s->penalty += END_OF_FILE_PENALTY;
601
602 /*
603 * Set post_blank to the number of blank lines following the split,
604 * including the line immediately after the split:
605 */
606 post_blank = (m->indent == -1) ? 1 + m->post_blank : 0;
607 total_blank = m->pre_blank + post_blank;
608
609 /* Penalties based on nearby blank lines: */
610 s->penalty += TOTAL_BLANK_WEIGHT * total_blank;
611 s->penalty += POST_BLANK_WEIGHT * post_blank;
612
613 if (m->indent != -1)
614 indent = m->indent;
615 else
616 indent = m->post_indent;
617
618 any_blanks = (total_blank != 0);
619
620 /* Note that the effective indent is -1 at the end of the file: */
621 s->effective_indent += indent;
622
623 if (indent == -1) {
624 /* No additional adjustments needed. */
625 } else if (m->pre_indent == -1) {
626 /* No additional adjustments needed. */
627 } else if (indent > m->pre_indent) {
628 /*
629 * The line is indented more than its predecessor.
630 */
631 s->penalty += any_blanks ?
632 RELATIVE_INDENT_WITH_BLANK_PENALTY :
633 RELATIVE_INDENT_PENALTY;
634 } else if (indent == m->pre_indent) {
635 /*
636 * The line has the same indentation level as its predecessor.
637 * No additional adjustments needed.
638 */
639 } else {
640 /*
641 * The line is indented less than its predecessor. It could be
642 * the block terminator of the previous block, but it could
643 * also be the start of a new block (e.g., an "else" block, or
644 * maybe the previous block didn't have a block terminator).
645 * Try to distinguish those cases based on what comes next:
646 */
647 if (m->post_indent != -1 && m->post_indent > indent) {
648 /*
649 * The following line is indented more. So it is likely
650 * that this line is the start of a block.
651 */
652 s->penalty += any_blanks ?
653 RELATIVE_OUTDENT_WITH_BLANK_PENALTY :
654 RELATIVE_OUTDENT_PENALTY;
655 } else {
656 /*
657 * That was probably the end of a block.
658 */
659 s->penalty += any_blanks ?
660 RELATIVE_DEDENT_WITH_BLANK_PENALTY :
661 RELATIVE_DEDENT_PENALTY;
662 }
663 }
664 }
665
666 static int score_cmp(struct split_score *s1, struct split_score *s2)
667 {
668 /* -1 if s1.effective_indent < s2->effective_indent, etc. */
669 int cmp_indents = ((s1->effective_indent > s2->effective_indent) -
670 (s1->effective_indent < s2->effective_indent));
671
672 return INDENT_WEIGHT * cmp_indents + (s1->penalty - s2->penalty);
673 }
674
675 /*
676 * Represent a group of changed lines in an xdfile_t (i.e., a contiguous group
677 * of lines that was inserted or deleted from the corresponding version of the
678 * file). We consider there to be such a group at the beginning of the file, at
679 * the end of the file, and between any two unchanged lines, though most such
680 * groups will usually be empty.
681 *
682 * If the first line in a group is equal to the line following the group, then
683 * the group can be slid down. Similarly, if the last line in a group is equal
684 * to the line preceding the group, then the group can be slid up. See
685 * group_slide_down() and group_slide_up().
686 *
687 * Note that loops that are testing for changed lines in xdf->rchg do not need
688 * index bounding since the array is prepared with a zero at position -1 and N.
689 */
690 struct xdlgroup {
691 /*
692 * The index of the first changed line in the group, or the index of
693 * the unchanged line above which the (empty) group is located.
694 */
695 long start;
696
697 /*
698 * The index of the first unchanged line after the group. For an empty
699 * group, end is equal to start.
700 */
701 long end;
702 };
703
704 /*
705 * Initialize g to point at the first group in xdf.
706 */
707 static void group_init(xdfile_t *xdf, struct xdlgroup *g)
708 {
709 g->start = g->end = 0;
710 while (xdf->changed[g->end])
711 g->end++;
712 }
713
714 /*
715 * Move g to describe the next (possibly empty) group in xdf and return 0. If g
716 * is already at the end of the file, do nothing and return -1.
717 */
718 static inline int group_next(xdfile_t *xdf, struct xdlgroup *g)
719 {
720 if (g->end == (long)xdf->nrec)
721 return -1;
722
723 g->start = g->end + 1;
724 for (g->end = g->start; xdf->changed[g->end]; g->end++)
725 ;
726
727 return 0;
728 }
729
730 /*
731 * Move g to describe the previous (possibly empty) group in xdf and return 0.
732 * If g is already at the beginning of the file, do nothing and return -1.
733 */
734 static inline int group_previous(xdfile_t *xdf, struct xdlgroup *g)
735 {
736 if (g->start == 0)
737 return -1;
738
739 g->end = g->start - 1;
740 for (g->start = g->end; xdf->changed[g->start - 1]; g->start--)
741 ;
742
743 return 0;
744 }
745
746 /*
747 * If g can be slid toward the end of the file, do so, and if it bumps into a
748 * following group, expand this group to include it. Return 0 on success or -1
749 * if g cannot be slid down.
750 */
751 static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g)
752 {
753 if (g->end < (long)xdf->nrec &&
754 recs_match(&xdf->recs[g->start], &xdf->recs[g->end])) {
755 xdf->changed[g->start++] = false;
756 xdf->changed[g->end++] = true;
757
758 while (xdf->changed[g->end])
759 g->end++;
760
761 return 0;
762 } else {
763 return -1;
764 }
765 }
766
767 /*
768 * If g can be slid toward the beginning of the file, do so, and if it bumps
769 * into a previous group, expand this group to include it. Return 0 on success
770 * or -1 if g cannot be slid up.
771 */
772 static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g)
773 {
774 if (g->start > 0 &&
775 recs_match(&xdf->recs[g->start - 1], &xdf->recs[g->end - 1])) {
776 xdf->changed[--g->start] = true;
777 xdf->changed[--g->end] = false;
778
779 while (xdf->changed[g->start - 1])
780 g->start--;
781
782 return 0;
783 } else {
784 return -1;
785 }
786 }
787
788 /*
789 * Move back and forward change groups for a consistent and pretty diff output.
790 * This also helps in finding joinable change groups and reducing the diff
791 * size.
792 */
793 int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
794 struct xdlgroup g, go;
795 struct xdlgroup g_orig;
796 long earliest_end, end_matching_other;
797 long groupsize;
798
799 group_init(xdf, &g);
800 group_init(xdfo, &go);
801
802 while (1) {
803 /*
804 * If the group is empty in the to-be-compacted file, skip it:
805 */
806 if (g.end == g.start)
807 goto next;
808
809 g_orig = g;
810
811 /*
812 * Now shift the change up and then down as far as possible in
813 * each direction. If it bumps into any other changes, merge
814 * them and restart the process.
815 */
816 do {
817 groupsize = g.end - g.start;
818
819 /*
820 * Keep track of the last "end" index that causes this
821 * group to align with a group of changed lines in the
822 * other file. -1 indicates that we haven't found such
823 * a match yet:
824 */
825 end_matching_other = -1;
826
827 /* Shift the group backward as much as possible: */
828 while (!group_slide_up(xdf, &g))
829 if (group_previous(xdfo, &go))
830 BUG("group sync broken sliding up");
831
832 /*
833 * This is this highest that this group can be shifted.
834 * Record its end index:
835 */
836 earliest_end = g.end;
837
838 if (go.end > go.start)
839 end_matching_other = g.end;
840
841 /* Now shift the group forward as far as possible: */
842 while (1) {
843 if (group_slide_down(xdf, &g))
844 break;
845 if (group_next(xdfo, &go))
846 BUG("group sync broken sliding down");
847
848 if (go.end > go.start)
849 end_matching_other = g.end;
850 }
851 } while (groupsize != g.end - g.start);
852
853 /*
854 * If the group can be shifted, then we can possibly use this
855 * freedom to produce a more intuitive diff.
856 *
857 * The group is currently shifted as far down as possible, so
858 * the heuristics below only have to handle upwards shifts.
859 */
860
861 if (g.end == earliest_end) {
862 /* no shifting was possible */
863 } else if (end_matching_other != -1) {
864 /*
865 * Move the possibly merged group of changes back to
866 * line up with the last group of changes from the
867 * other file that it can align with. This avoids breaking
868 * a single change into a separate addition/deletion.
869 */
870 while (go.end == go.start) {
871 if (group_slide_up(xdf, &g))
872 BUG("match disappeared");
873 if (group_previous(xdfo, &go))
874 BUG("group sync broken sliding to match");
875 }
876 } else if (flags & XDF_INDENT_HEURISTIC) {
877 /*
878 * Indent heuristic: a group of pure add/delete lines
879 * implies two splits, one between the end of the
880 * "before" context and the start of the group, and
881 * another between the end of the group and the
882 * beginning of the "after" context. Some splits are
883 * aesthetically better and some are worse. We compute
884 * a badness "score" for each split, and add the scores
885 * for the two splits to define a "score" for each
886 * position that the group can be shifted to. Then we
887 * pick the shift with the lowest score.
888 */
889 long shift, best_shift = -1;
890 struct split_score best_score;
891
892 shift = earliest_end;
893 if (g.end - groupsize - 1 > shift)
894 shift = g.end - groupsize - 1;
895 if (g.end - INDENT_HEURISTIC_MAX_SLIDING > shift)
896 shift = g.end - INDENT_HEURISTIC_MAX_SLIDING;
897 for (; shift <= g.end; shift++) {
898 struct split_measurement m;
899 struct split_score score = {0, 0};
900
901 measure_split(xdf, shift, &m);
902 score_add_split(&m, &score);
903 measure_split(xdf, shift - groupsize, &m);
904 score_add_split(&m, &score);
905 if (best_shift == -1 ||
906 score_cmp(&score, &best_score) <= 0) {
907 best_score.effective_indent = score.effective_indent;
908 best_score.penalty = score.penalty;
909 best_shift = shift;
910 }
911 }
912
913 while (g.end > best_shift) {
914 if (group_slide_up(xdf, &g))
915 BUG("best shift unreached");
916 if (group_previous(xdfo, &go))
917 BUG("group sync broken sliding to blank line");
918 }
919 }
920
921 /*
922 * If we merged change groups during shifting, the new
923 * combined group could now have matching lines in both files,
924 * even if the original separate groups did not. Re-diff the
925 * new group to find these matching lines to mark them as
926 * unchanged.
927 *
928 * Only do this if the corresponding group in the other file is
929 * non-empty, as it's trivial otherwise.
930 *
931 * Only do this for histogram diff as its LCS algorithm allows
932 * for this scenario. In contrast, patience diff finds LCS
933 * of unique lines that groups cannot be shifted across.
934 * Myer's diff (standalone or used as fall-back in patience
935 * diff) already finds minimal edits so it is not possible for
936 * shifted groups to result in a smaller diff. (Without
937 * XDF_NEED_MINIMAL, Myer's isn't technically guaranteed to be
938 * minimal, but it should be so most of the time)
939 */
940 if (go.end != go.start &&
941 XDF_DIFF_ALG(flags) == XDF_HISTOGRAM_DIFF &&
942 (g.start != g_orig.start ||
943 g.end != g_orig.end)) {
944 xpparam_t xpp;
945 xdfenv_t xe;
946
947 memset(&xpp, 0, sizeof(xpp));
948 xpp.flags = flags & ~XDF_DIFF_ALGORITHM_MASK;
949
950 xe.xdf1 = *xdf;
951 xe.xdf2 = *xdfo;
952
953 if (xdl_fall_back_diff(&xe, &xpp,
954 g.start + 1, g.end - g.start,
955 go.start + 1, go.end - go.start)) {
956 return -1;
957 }
958 }
959
960 next:
961 /* Move past the just-processed group: */
962 if (group_next(xdf, &g))
963 break;
964 if (group_next(xdfo, &go))
965 BUG("group sync broken moving to next group");
966 }
967
968 if (!group_next(xdfo, &go))
969 BUG("group sync broken at end of file");
970
971 return 0;
972 }
973
974
975 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
976 xdchange_t *cscr = NULL, *xch;
977 bool *changed1 = xe->xdf1.changed, *changed2 = xe->xdf2.changed;
978 long i1, i2, l1, l2;
979
980 /*
981 * Trivial. Collects "groups" of changes and creates an edit script.
982 */
983 for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
984 if (changed1[i1 - 1] || changed2[i2 - 1]) {
985 for (l1 = i1; changed1[i1 - 1]; i1--);
986 for (l2 = i2; changed2[i2 - 1]; i2--);
987
988 if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
989 xdl_free_script(cscr);
990 return -1;
991 }
992 cscr = xch;
993 }
994
995 *xscr = cscr;
996
997 return 0;
998 }
999
1000
1001 void xdl_free_script(xdchange_t *xscr) {
1002 xdchange_t *xch;
1003
1004 while ((xch = xscr) != NULL) {
1005 xscr = xscr->next;
1006 xdl_free(xch);
1007 }
1008 }
1009
1010 static int xdl_call_hunk_func(xdfenv_t *xe UNUSED, xdchange_t *xscr, xdemitcb_t *ecb,
1011 xdemitconf_t const *xecfg)
1012 {
1013 xdchange_t *xch, *xche;
1014
1015 for (xch = xscr; xch; xch = xche->next) {
1016 xche = xdl_get_hunk(&xch, xecfg);
1017 if (!xch)
1018 break;
1019 if (xecfg->hunk_func(xch->i1, xche->i1 + xche->chg1 - xch->i1,
1020 xch->i2, xche->i2 + xche->chg2 - xch->i2,
1021 ecb->priv) < 0)
1022 return -1;
1023 }
1024 return 0;
1025 }
1026
1027 static void xdl_mark_ignorable_lines(xdchange_t *xscr, xdfenv_t *xe, long flags)
1028 {
1029 xdchange_t *xch;
1030
1031 for (xch = xscr; xch; xch = xch->next) {
1032 int ignore = 1;
1033 xrecord_t *rec;
1034 long i;
1035
1036 rec = &xe->xdf1.recs[xch->i1];
1037 for (i = 0; i < xch->chg1 && ignore; i++)
1038 ignore = xdl_blankline((const char *)rec[i].ptr, (long)rec[i].size, flags);
1039
1040 rec = &xe->xdf2.recs[xch->i2];
1041 for (i = 0; i < xch->chg2 && ignore; i++)
1042 ignore = xdl_blankline((const char *)rec[i].ptr, (long)rec[i].size, flags);
1043
1044 xch->ignore = ignore;
1045 }
1046 }
1047
1048 static int record_matches_regex(xrecord_t *rec, xpparam_t const *xpp) {
1049 regmatch_t regmatch;
1050 size_t i;
1051
1052 for (i = 0; i < xpp->ignore_regex_nr; i++)
1053 if (!regexec_buf(xpp->ignore_regex[i], (const char *)rec->ptr, rec->size, 1,
1054 &regmatch, 0))
1055 return 1;
1056
1057 return 0;
1058 }
1059
1060 static void xdl_mark_ignorable_regex(xdchange_t *xscr, const xdfenv_t *xe,
1061 xpparam_t const *xpp)
1062 {
1063 xdchange_t *xch;
1064
1065 for (xch = xscr; xch; xch = xch->next) {
1066 xrecord_t *rec;
1067 int ignore = 1;
1068 long i;
1069
1070 /*
1071 * Do not override --ignore-blank-lines.
1072 */
1073 if (xch->ignore)
1074 continue;
1075
1076 rec = &xe->xdf1.recs[xch->i1];
1077 for (i = 0; i < xch->chg1 && ignore; i++)
1078 ignore = record_matches_regex(&rec[i], xpp);
1079
1080 rec = &xe->xdf2.recs[xch->i2];
1081 for (i = 0; i < xch->chg2 && ignore; i++)
1082 ignore = record_matches_regex(&rec[i], xpp);
1083
1084 xch->ignore = ignore;
1085 }
1086 }
1087
1088 int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
1089 xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
1090 xdchange_t *xscr;
1091 xdfenv_t xe;
1092 emit_func_t ef = xecfg->hunk_func ? xdl_call_hunk_func : xdl_emit_diff;
1093
1094 if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
1095
1096 return -1;
1097 }
1098 if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
1099 xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
1100 xdl_build_script(&xe, &xscr) < 0) {
1101
1102 xdl_free_env(&xe);
1103 return -1;
1104 }
1105 if (xscr) {
1106 if (xpp->flags & XDF_IGNORE_BLANK_LINES)
1107 xdl_mark_ignorable_lines(xscr, &xe, xpp->flags);
1108
1109 if (xpp->ignore_regex)
1110 xdl_mark_ignorable_regex(xscr, &xe, xpp);
1111
1112 if (ef(&xe, xscr, ecb, xecfg) < 0) {
1113
1114 xdl_free_script(xscr);
1115 xdl_free_env(&xe);
1116 return -1;
1117 }
1118 xdl_free_script(xscr);
1119 }
1120 xdl_free_env(&xe);
1121
1122 return 0;
1123 }