Merge branch 'rb/hpe'
[git.git] / xdiff / xdiffi.c
blob1f1f4a3c7808435f73b0ffd1c35d5b0572516b6c
1 /*
2 * LibXDiff by Davide Libenzi ( File Differential Library )
3 * Copyright (C) 2003 Davide Libenzi
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.
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.
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/>.
19 * Davide Libenzi <davidel@xmailserver.org>
23 #include "xinclude.h"
25 #define XDL_MAX_COST_MIN 256
26 #define XDL_HEUR_MIN_COST 256
27 #define XDL_LINE_MAX (long)((1UL << (CHAR_BIT * sizeof(long) - 1)) - 1)
28 #define XDL_SNAKE_CNT 20
29 #define XDL_K_HEUR 4
31 typedef struct s_xdpsplit {
32 long i1, i2;
33 int min_lo, min_hi;
34 } xdpsplit_t;
37 * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
38 * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
39 * the forward diagonal starting from (off1, off2) and the backward diagonal
40 * starting from (lim1, lim2). If the K values on the same diagonal crosses
41 * returns the furthest point of reach. We might end up having to expensive
42 * cases using this algorithm is full, so a little bit of heuristic is needed
43 * to cut the search and to return a suboptimal point.
45 static long xdl_split(unsigned long const *ha1, long off1, long lim1,
46 unsigned long const *ha2, long off2, long lim2,
47 long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
48 xdalgoenv_t *xenv) {
49 long dmin = off1 - lim2, dmax = lim1 - off2;
50 long fmid = off1 - off2, bmid = lim1 - lim2;
51 long odd = (fmid - bmid) & 1;
52 long fmin = fmid, fmax = fmid;
53 long bmin = bmid, bmax = bmid;
54 long ec, d, i1, i2, prev1, best, dd, v, k;
57 * Set initial diagonal values for both forward and backward path.
59 kvdf[fmid] = off1;
60 kvdb[bmid] = lim1;
62 for (ec = 1;; ec++) {
63 int got_snake = 0;
66 * We need to extent the diagonal "domain" by one. If the next
67 * values exits the box boundaries we need to change it in the
68 * opposite direction because (max - min) must be a power of two.
69 * Also we initialize the external K value to -1 so that we can
70 * avoid extra conditions check inside the core loop.
72 if (fmin > dmin)
73 kvdf[--fmin - 1] = -1;
74 else
75 ++fmin;
76 if (fmax < dmax)
77 kvdf[++fmax + 1] = -1;
78 else
79 --fmax;
81 for (d = fmax; d >= fmin; d -= 2) {
82 if (kvdf[d - 1] >= kvdf[d + 1])
83 i1 = kvdf[d - 1] + 1;
84 else
85 i1 = kvdf[d + 1];
86 prev1 = i1;
87 i2 = i1 - d;
88 for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
89 if (i1 - prev1 > xenv->snake_cnt)
90 got_snake = 1;
91 kvdf[d] = i1;
92 if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
93 spl->i1 = i1;
94 spl->i2 = i2;
95 spl->min_lo = spl->min_hi = 1;
96 return ec;
101 * We need to extent the diagonal "domain" by one. If the next
102 * values exits the box boundaries we need to change it in the
103 * opposite direction because (max - min) must be a power of two.
104 * Also we initialize the external K value to -1 so that we can
105 * avoid extra conditions check inside the core loop.
107 if (bmin > dmin)
108 kvdb[--bmin - 1] = XDL_LINE_MAX;
109 else
110 ++bmin;
111 if (bmax < dmax)
112 kvdb[++bmax + 1] = XDL_LINE_MAX;
113 else
114 --bmax;
116 for (d = bmax; d >= bmin; d -= 2) {
117 if (kvdb[d - 1] < kvdb[d + 1])
118 i1 = kvdb[d - 1];
119 else
120 i1 = kvdb[d + 1] - 1;
121 prev1 = i1;
122 i2 = i1 - d;
123 for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
124 if (prev1 - i1 > xenv->snake_cnt)
125 got_snake = 1;
126 kvdb[d] = i1;
127 if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
128 spl->i1 = i1;
129 spl->i2 = i2;
130 spl->min_lo = spl->min_hi = 1;
131 return ec;
135 if (need_min)
136 continue;
139 * If the edit cost is above the heuristic trigger and if
140 * we got a good snake, we sample current diagonals to see
141 * if some of the, have reached an "interesting" path. Our
142 * measure is a function of the distance from the diagonal
143 * corner (i1 + i2) penalized with the distance from the
144 * mid diagonal itself. If this value is above the current
145 * edit cost times a magic factor (XDL_K_HEUR) we consider
146 * it interesting.
148 if (got_snake && ec > xenv->heur_min) {
149 for (best = 0, d = fmax; d >= fmin; d -= 2) {
150 dd = d > fmid ? d - fmid: fmid - d;
151 i1 = kvdf[d];
152 i2 = i1 - d;
153 v = (i1 - off1) + (i2 - off2) - dd;
155 if (v > XDL_K_HEUR * ec && v > best &&
156 off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
157 off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
158 for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
159 if (k == xenv->snake_cnt) {
160 best = v;
161 spl->i1 = i1;
162 spl->i2 = i2;
163 break;
167 if (best > 0) {
168 spl->min_lo = 1;
169 spl->min_hi = 0;
170 return ec;
173 for (best = 0, d = bmax; d >= bmin; d -= 2) {
174 dd = d > bmid ? d - bmid: bmid - d;
175 i1 = kvdb[d];
176 i2 = i1 - d;
177 v = (lim1 - i1) + (lim2 - i2) - dd;
179 if (v > XDL_K_HEUR * ec && v > best &&
180 off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
181 off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
182 for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
183 if (k == xenv->snake_cnt - 1) {
184 best = v;
185 spl->i1 = i1;
186 spl->i2 = i2;
187 break;
191 if (best > 0) {
192 spl->min_lo = 0;
193 spl->min_hi = 1;
194 return ec;
199 * Enough is enough. We spent too much time here and now we collect
200 * the furthest reaching path using the (i1 + i2) measure.
202 if (ec >= xenv->mxcost) {
203 long fbest, fbest1, bbest, bbest1;
205 fbest = fbest1 = -1;
206 for (d = fmax; d >= fmin; d -= 2) {
207 i1 = XDL_MIN(kvdf[d], lim1);
208 i2 = i1 - d;
209 if (lim2 < i2)
210 i1 = lim2 + d, i2 = lim2;
211 if (fbest < i1 + i2) {
212 fbest = i1 + i2;
213 fbest1 = i1;
217 bbest = bbest1 = XDL_LINE_MAX;
218 for (d = bmax; d >= bmin; d -= 2) {
219 i1 = XDL_MAX(off1, kvdb[d]);
220 i2 = i1 - d;
221 if (i2 < off2)
222 i1 = off2 + d, i2 = off2;
223 if (i1 + i2 < bbest) {
224 bbest = i1 + i2;
225 bbest1 = i1;
229 if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
230 spl->i1 = fbest1;
231 spl->i2 = fbest - fbest1;
232 spl->min_lo = 1;
233 spl->min_hi = 0;
234 } else {
235 spl->i1 = bbest1;
236 spl->i2 = bbest - bbest1;
237 spl->min_lo = 0;
238 spl->min_hi = 1;
240 return ec;
247 * Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
248 * the box splitting function. Note that the real job (marking changed lines)
249 * is done in the two boundary reaching checks.
251 int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
252 diffdata_t *dd2, long off2, long lim2,
253 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
254 unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;
257 * Shrink the box by walking through each diagonal snake (SW and NE).
259 for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
260 for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
263 * If one dimension is empty, then all records on the other one must
264 * be obviously changed.
266 if (off1 == lim1) {
267 char *rchg2 = dd2->rchg;
268 long *rindex2 = dd2->rindex;
270 for (; off2 < lim2; off2++)
271 rchg2[rindex2[off2]] = 1;
272 } else if (off2 == lim2) {
273 char *rchg1 = dd1->rchg;
274 long *rindex1 = dd1->rindex;
276 for (; off1 < lim1; off1++)
277 rchg1[rindex1[off1]] = 1;
278 } else {
279 xdpsplit_t spl;
280 spl.i1 = spl.i2 = 0;
283 * Divide ...
285 if (xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
286 need_min, &spl, xenv) < 0) {
288 return -1;
292 * ... et Impera.
294 if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
295 kvdf, kvdb, spl.min_lo, xenv) < 0 ||
296 xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
297 kvdf, kvdb, spl.min_hi, xenv) < 0) {
299 return -1;
303 return 0;
307 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
308 xdfenv_t *xe) {
309 long ndiags;
310 long *kvd, *kvdf, *kvdb;
311 xdalgoenv_t xenv;
312 diffdata_t dd1, dd2;
314 if (XDF_DIFF_ALG(xpp->flags) == XDF_PATIENCE_DIFF)
315 return xdl_do_patience_diff(mf1, mf2, xpp, xe);
317 if (XDF_DIFF_ALG(xpp->flags) == XDF_HISTOGRAM_DIFF)
318 return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
320 if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
322 return -1;
326 * Allocate and setup K vectors to be used by the differential algorithm.
327 * One is to store the forward path and one to store the backward path.
329 ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
330 if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
332 xdl_free_env(xe);
333 return -1;
335 kvdf = kvd;
336 kvdb = kvdf + ndiags;
337 kvdf += xe->xdf2.nreff + 1;
338 kvdb += xe->xdf2.nreff + 1;
340 xenv.mxcost = xdl_bogosqrt(ndiags);
341 if (xenv.mxcost < XDL_MAX_COST_MIN)
342 xenv.mxcost = XDL_MAX_COST_MIN;
343 xenv.snake_cnt = XDL_SNAKE_CNT;
344 xenv.heur_min = XDL_HEUR_MIN_COST;
346 dd1.nrec = xe->xdf1.nreff;
347 dd1.ha = xe->xdf1.ha;
348 dd1.rchg = xe->xdf1.rchg;
349 dd1.rindex = xe->xdf1.rindex;
350 dd2.nrec = xe->xdf2.nreff;
351 dd2.ha = xe->xdf2.ha;
352 dd2.rchg = xe->xdf2.rchg;
353 dd2.rindex = xe->xdf2.rindex;
355 if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
356 kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
358 xdl_free(kvd);
359 xdl_free_env(xe);
360 return -1;
363 xdl_free(kvd);
365 return 0;
369 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
370 xdchange_t *xch;
372 if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
373 return NULL;
375 xch->next = xscr;
376 xch->i1 = i1;
377 xch->i2 = i2;
378 xch->chg1 = chg1;
379 xch->chg2 = chg2;
380 xch->ignore = 0;
382 return xch;
386 static int recs_match(xrecord_t *rec1, xrecord_t *rec2, long flags)
388 return (rec1->ha == rec2->ha &&
389 xdl_recmatch(rec1->ptr, rec1->size,
390 rec2->ptr, rec2->size,
391 flags));
395 * If a line is indented more than this, get_indent() just returns this value.
396 * This avoids having to do absurd amounts of work for data that are not
397 * human-readable text, and also ensures that the output of get_indent fits within
398 * an int.
400 #define MAX_INDENT 200
403 * Return the amount of indentation of the specified line, treating TAB as 8
404 * columns. Return -1 if line is empty or contains only whitespace. Clamp the
405 * output value at MAX_INDENT.
407 static int get_indent(xrecord_t *rec)
409 long i;
410 int ret = 0;
412 for (i = 0; i < rec->size; i++) {
413 char c = rec->ptr[i];
415 if (!XDL_ISSPACE(c))
416 return ret;
417 else if (c == ' ')
418 ret += 1;
419 else if (c == '\t')
420 ret += 8 - ret % 8;
421 /* ignore other whitespace characters */
423 if (ret >= MAX_INDENT)
424 return MAX_INDENT;
427 /* The line contains only whitespace. */
428 return -1;
432 * If more than this number of consecutive blank rows are found, just return this
433 * value. This avoids requiring O(N^2) work for pathological cases, and also
434 * ensures that the output of score_split fits in an int.
436 #define MAX_BLANKS 20
438 /* Characteristics measured about a hypothetical split position. */
439 struct split_measurement {
441 * Is the split at the end of the file (aside from any blank lines)?
443 int end_of_file;
446 * How much is the line immediately following the split indented (or -1 if
447 * the line is blank):
449 int indent;
452 * How many consecutive lines above the split are blank?
454 int pre_blank;
457 * How much is the nearest non-blank line above the split indented (or -1
458 * if there is no such line)?
460 int pre_indent;
463 * How many lines after the line following the split are blank?
465 int post_blank;
468 * How much is the nearest non-blank line after the line following the
469 * split indented (or -1 if there is no such line)?
471 int post_indent;
474 struct split_score {
475 /* The effective indent of this split (smaller is preferred). */
476 int effective_indent;
478 /* Penalty for this split (smaller is preferred). */
479 int penalty;
483 * Fill m with information about a hypothetical split of xdf above line split.
485 static void measure_split(const xdfile_t *xdf, long split,
486 struct split_measurement *m)
488 long i;
490 if (split >= xdf->nrec) {
491 m->end_of_file = 1;
492 m->indent = -1;
493 } else {
494 m->end_of_file = 0;
495 m->indent = get_indent(xdf->recs[split]);
498 m->pre_blank = 0;
499 m->pre_indent = -1;
500 for (i = split - 1; i >= 0; i--) {
501 m->pre_indent = get_indent(xdf->recs[i]);
502 if (m->pre_indent != -1)
503 break;
504 m->pre_blank += 1;
505 if (m->pre_blank == MAX_BLANKS) {
506 m->pre_indent = 0;
507 break;
511 m->post_blank = 0;
512 m->post_indent = -1;
513 for (i = split + 1; i < xdf->nrec; i++) {
514 m->post_indent = get_indent(xdf->recs[i]);
515 if (m->post_indent != -1)
516 break;
517 m->post_blank += 1;
518 if (m->post_blank == MAX_BLANKS) {
519 m->post_indent = 0;
520 break;
526 * The empirically-determined weight factors used by score_split() below.
527 * Larger values means that the position is a less favorable place to split.
529 * Note that scores are only ever compared against each other, so multiplying
530 * all of these weight/penalty values by the same factor wouldn't change the
531 * heuristic's behavior. Still, we need to set that arbitrary scale *somehow*.
532 * In practice, these numbers are chosen to be large enough that they can be
533 * adjusted relative to each other with sufficient precision despite using
534 * integer math.
537 /* Penalty if there are no non-blank lines before the split */
538 #define START_OF_FILE_PENALTY 1
540 /* Penalty if there are no non-blank lines after the split */
541 #define END_OF_FILE_PENALTY 21
543 /* Multiplier for the number of blank lines around the split */
544 #define TOTAL_BLANK_WEIGHT (-30)
546 /* Multiplier for the number of blank lines after the split */
547 #define POST_BLANK_WEIGHT 6
550 * Penalties applied if the line is indented more than its predecessor
552 #define RELATIVE_INDENT_PENALTY (-4)
553 #define RELATIVE_INDENT_WITH_BLANK_PENALTY 10
556 * Penalties applied if the line is indented less than both its predecessor and
557 * its successor
559 #define RELATIVE_OUTDENT_PENALTY 24
560 #define RELATIVE_OUTDENT_WITH_BLANK_PENALTY 17
563 * Penalties applied if the line is indented less than its predecessor but not
564 * less than its successor
566 #define RELATIVE_DEDENT_PENALTY 23
567 #define RELATIVE_DEDENT_WITH_BLANK_PENALTY 17
570 * We only consider whether the sum of the effective indents for splits are
571 * less than (-1), equal to (0), or greater than (+1) each other. The resulting
572 * value is multiplied by the following weight and combined with the penalty to
573 * determine the better of two scores.
575 #define INDENT_WEIGHT 60
578 * How far do we slide a hunk at most?
580 #define INDENT_HEURISTIC_MAX_SLIDING 100
583 * Compute a badness score for the hypothetical split whose measurements are
584 * stored in m. The weight factors were determined empirically using the tools and
585 * corpus described in
587 * https://github.com/mhagger/diff-slider-tools
589 * Also see that project if you want to improve the weights based on, for example,
590 * a larger or more diverse corpus.
592 static void score_add_split(const struct split_measurement *m, struct split_score *s)
595 * A place to accumulate penalty factors (positive makes this index more
596 * favored):
598 int post_blank, total_blank, indent, any_blanks;
600 if (m->pre_indent == -1 && m->pre_blank == 0)
601 s->penalty += START_OF_FILE_PENALTY;
603 if (m->end_of_file)
604 s->penalty += END_OF_FILE_PENALTY;
607 * Set post_blank to the number of blank lines following the split,
608 * including the line immediately after the split:
610 post_blank = (m->indent == -1) ? 1 + m->post_blank : 0;
611 total_blank = m->pre_blank + post_blank;
613 /* Penalties based on nearby blank lines: */
614 s->penalty += TOTAL_BLANK_WEIGHT * total_blank;
615 s->penalty += POST_BLANK_WEIGHT * post_blank;
617 if (m->indent != -1)
618 indent = m->indent;
619 else
620 indent = m->post_indent;
622 any_blanks = (total_blank != 0);
624 /* Note that the effective indent is -1 at the end of the file: */
625 s->effective_indent += indent;
627 if (indent == -1) {
628 /* No additional adjustments needed. */
629 } else if (m->pre_indent == -1) {
630 /* No additional adjustments needed. */
631 } else if (indent > m->pre_indent) {
633 * The line is indented more than its predecessor.
635 s->penalty += any_blanks ?
636 RELATIVE_INDENT_WITH_BLANK_PENALTY :
637 RELATIVE_INDENT_PENALTY;
638 } else if (indent == m->pre_indent) {
640 * The line has the same indentation level as its predecessor.
641 * No additional adjustments needed.
643 } else {
645 * The line is indented less than its predecessor. It could be
646 * the block terminator of the previous block, but it could
647 * also be the start of a new block (e.g., an "else" block, or
648 * maybe the previous block didn't have a block terminator).
649 * Try to distinguish those cases based on what comes next:
651 if (m->post_indent != -1 && m->post_indent > indent) {
653 * The following line is indented more. So it is likely
654 * that this line is the start of a block.
656 s->penalty += any_blanks ?
657 RELATIVE_OUTDENT_WITH_BLANK_PENALTY :
658 RELATIVE_OUTDENT_PENALTY;
659 } else {
661 * That was probably the end of a block.
663 s->penalty += any_blanks ?
664 RELATIVE_DEDENT_WITH_BLANK_PENALTY :
665 RELATIVE_DEDENT_PENALTY;
670 static int score_cmp(struct split_score *s1, struct split_score *s2)
672 /* -1 if s1.effective_indent < s2->effective_indent, etc. */
673 int cmp_indents = ((s1->effective_indent > s2->effective_indent) -
674 (s1->effective_indent < s2->effective_indent));
676 return INDENT_WEIGHT * cmp_indents + (s1->penalty - s2->penalty);
680 * Represent a group of changed lines in an xdfile_t (i.e., a contiguous group
681 * of lines that was inserted or deleted from the corresponding version of the
682 * file). We consider there to be such a group at the beginning of the file, at
683 * the end of the file, and between any two unchanged lines, though most such
684 * groups will usually be empty.
686 * If the first line in a group is equal to the line following the group, then
687 * the group can be slid down. Similarly, if the last line in a group is equal
688 * to the line preceding the group, then the group can be slid up. See
689 * group_slide_down() and group_slide_up().
691 * Note that loops that are testing for changed lines in xdf->rchg do not need
692 * index bounding since the array is prepared with a zero at position -1 and N.
694 struct xdlgroup {
696 * The index of the first changed line in the group, or the index of
697 * the unchanged line above which the (empty) group is located.
699 long start;
702 * The index of the first unchanged line after the group. For an empty
703 * group, end is equal to start.
705 long end;
709 * Initialize g to point at the first group in xdf.
711 static void group_init(xdfile_t *xdf, struct xdlgroup *g)
713 g->start = g->end = 0;
714 while (xdf->rchg[g->end])
715 g->end++;
719 * Move g to describe the next (possibly empty) group in xdf and return 0. If g
720 * is already at the end of the file, do nothing and return -1.
722 static inline int group_next(xdfile_t *xdf, struct xdlgroup *g)
724 if (g->end == xdf->nrec)
725 return -1;
727 g->start = g->end + 1;
728 for (g->end = g->start; xdf->rchg[g->end]; g->end++)
731 return 0;
735 * Move g to describe the previous (possibly empty) group in xdf and return 0.
736 * If g is already at the beginning of the file, do nothing and return -1.
738 static inline int group_previous(xdfile_t *xdf, struct xdlgroup *g)
740 if (g->start == 0)
741 return -1;
743 g->end = g->start - 1;
744 for (g->start = g->end; xdf->rchg[g->start - 1]; g->start--)
747 return 0;
751 * If g can be slid toward the end of the file, do so, and if it bumps into a
752 * following group, expand this group to include it. Return 0 on success or -1
753 * if g cannot be slid down.
755 static int group_slide_down(xdfile_t *xdf, struct xdlgroup *g, long flags)
757 if (g->end < xdf->nrec &&
758 recs_match(xdf->recs[g->start], xdf->recs[g->end], flags)) {
759 xdf->rchg[g->start++] = 0;
760 xdf->rchg[g->end++] = 1;
762 while (xdf->rchg[g->end])
763 g->end++;
765 return 0;
766 } else {
767 return -1;
772 * If g can be slid toward the beginning of the file, do so, and if it bumps
773 * into a previous group, expand this group to include it. Return 0 on success
774 * or -1 if g cannot be slid up.
776 static int group_slide_up(xdfile_t *xdf, struct xdlgroup *g, long flags)
778 if (g->start > 0 &&
779 recs_match(xdf->recs[g->start - 1], xdf->recs[g->end - 1], flags)) {
780 xdf->rchg[--g->start] = 1;
781 xdf->rchg[--g->end] = 0;
783 while (xdf->rchg[g->start - 1])
784 g->start--;
786 return 0;
787 } else {
788 return -1;
792 static void xdl_bug(const char *msg)
794 fprintf(stderr, "BUG: %s\n", msg);
795 exit(1);
799 * Move back and forward change groups for a consistent and pretty diff output.
800 * This also helps in finding joinable change groups and reducing the diff
801 * size.
803 int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
804 struct xdlgroup g, go;
805 long earliest_end, end_matching_other;
806 long groupsize;
808 group_init(xdf, &g);
809 group_init(xdfo, &go);
811 while (1) {
812 /* If the group is empty in the to-be-compacted file, skip it: */
813 if (g.end == g.start)
814 goto next;
817 * Now shift the change up and then down as far as possible in
818 * each direction. If it bumps into any other changes, merge them.
820 do {
821 groupsize = g.end - g.start;
824 * Keep track of the last "end" index that causes this
825 * group to align with a group of changed lines in the
826 * other file. -1 indicates that we haven't found such
827 * a match yet:
829 end_matching_other = -1;
831 /* Shift the group backward as much as possible: */
832 while (!group_slide_up(xdf, &g, flags))
833 if (group_previous(xdfo, &go))
834 xdl_bug("group sync broken sliding up");
837 * This is this highest that this group can be shifted.
838 * Record its end index:
840 earliest_end = g.end;
842 if (go.end > go.start)
843 end_matching_other = g.end;
845 /* Now shift the group forward as far as possible: */
846 while (1) {
847 if (group_slide_down(xdf, &g, flags))
848 break;
849 if (group_next(xdfo, &go))
850 xdl_bug("group sync broken sliding down");
852 if (go.end > go.start)
853 end_matching_other = g.end;
855 } while (groupsize != g.end - g.start);
858 * If the group can be shifted, then we can possibly use this
859 * freedom to produce a more intuitive diff.
861 * The group is currently shifted as far down as possible, so the
862 * heuristics below only have to handle upwards shifts.
865 if (g.end == earliest_end) {
866 /* no shifting was possible */
867 } else if (end_matching_other != -1) {
869 * Move the possibly merged group of changes back to line
870 * up with the last group of changes from the other file
871 * that it can align with.
873 while (go.end == go.start) {
874 if (group_slide_up(xdf, &g, flags))
875 xdl_bug("match disappeared");
876 if (group_previous(xdfo, &go))
877 xdl_bug("group sync broken sliding to match");
879 } else if (flags & XDF_INDENT_HEURISTIC) {
881 * Indent heuristic: a group of pure add/delete lines
882 * implies two splits, one between the end of the "before"
883 * context and the start of the group, and another between
884 * the end of the group and the beginning of the "after"
885 * context. Some splits are aesthetically better and some
886 * are worse. We compute a badness "score" for each split,
887 * and add the scores for the two splits to define a
888 * "score" for each position that the group can be shifted
889 * to. Then we pick the shift with the lowest score.
891 long shift, best_shift = -1;
892 struct split_score best_score;
894 shift = earliest_end;
895 if (g.end - groupsize - 1 > shift)
896 shift = g.end - groupsize - 1;
897 if (g.end - INDENT_HEURISTIC_MAX_SLIDING > shift)
898 shift = g.end - INDENT_HEURISTIC_MAX_SLIDING;
899 for (; shift <= g.end; shift++) {
900 struct split_measurement m;
901 struct split_score score = {0, 0};
903 measure_split(xdf, shift, &m);
904 score_add_split(&m, &score);
905 measure_split(xdf, shift - groupsize, &m);
906 score_add_split(&m, &score);
907 if (best_shift == -1 ||
908 score_cmp(&score, &best_score) <= 0) {
909 best_score.effective_indent = score.effective_indent;
910 best_score.penalty = score.penalty;
911 best_shift = shift;
915 while (g.end > best_shift) {
916 if (group_slide_up(xdf, &g, flags))
917 xdl_bug("best shift unreached");
918 if (group_previous(xdfo, &go))
919 xdl_bug("group sync broken sliding to blank line");
923 next:
924 /* Move past the just-processed group: */
925 if (group_next(xdf, &g))
926 break;
927 if (group_next(xdfo, &go))
928 xdl_bug("group sync broken moving to next group");
931 if (!group_next(xdfo, &go))
932 xdl_bug("group sync broken at end of file");
934 return 0;
938 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
939 xdchange_t *cscr = NULL, *xch;
940 char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
941 long i1, i2, l1, l2;
944 * Trivial. Collects "groups" of changes and creates an edit script.
946 for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
947 if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
948 for (l1 = i1; rchg1[i1 - 1]; i1--);
949 for (l2 = i2; rchg2[i2 - 1]; i2--);
951 if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
952 xdl_free_script(cscr);
953 return -1;
955 cscr = xch;
958 *xscr = cscr;
960 return 0;
964 void xdl_free_script(xdchange_t *xscr) {
965 xdchange_t *xch;
967 while ((xch = xscr) != NULL) {
968 xscr = xscr->next;
969 xdl_free(xch);
973 static int xdl_call_hunk_func(xdfenv_t *xe, xdchange_t *xscr, xdemitcb_t *ecb,
974 xdemitconf_t const *xecfg)
976 xdchange_t *xch, *xche;
978 for (xch = xscr; xch; xch = xche->next) {
979 xche = xdl_get_hunk(&xch, xecfg);
980 if (!xch)
981 break;
982 if (xecfg->hunk_func(xch->i1, xche->i1 + xche->chg1 - xch->i1,
983 xch->i2, xche->i2 + xche->chg2 - xch->i2,
984 ecb->priv) < 0)
985 return -1;
987 return 0;
990 static void xdl_mark_ignorable(xdchange_t *xscr, xdfenv_t *xe, long flags)
992 xdchange_t *xch;
994 for (xch = xscr; xch; xch = xch->next) {
995 int ignore = 1;
996 xrecord_t **rec;
997 long i;
999 rec = &xe->xdf1.recs[xch->i1];
1000 for (i = 0; i < xch->chg1 && ignore; i++)
1001 ignore = xdl_blankline(rec[i]->ptr, rec[i]->size, flags);
1003 rec = &xe->xdf2.recs[xch->i2];
1004 for (i = 0; i < xch->chg2 && ignore; i++)
1005 ignore = xdl_blankline(rec[i]->ptr, rec[i]->size, flags);
1007 xch->ignore = ignore;
1011 int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
1012 xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
1013 xdchange_t *xscr;
1014 xdfenv_t xe;
1015 emit_func_t ef = xecfg->hunk_func ? xdl_call_hunk_func : xdl_emit_diff;
1017 if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
1019 return -1;
1021 if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
1022 xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
1023 xdl_build_script(&xe, &xscr) < 0) {
1025 xdl_free_env(&xe);
1026 return -1;
1028 if (xscr) {
1029 if (xpp->flags & XDF_IGNORE_BLANK_LINES)
1030 xdl_mark_ignorable(xscr, &xe, xpp->flags);
1032 if (ef(&xe, xscr, ecb, xecfg) < 0) {
1034 xdl_free_script(xscr);
1035 xdl_free_env(&xe);
1036 return -1;
1038 xdl_free_script(xscr);
1040 xdl_free_env(&xe);
1042 return 0;