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[git/git.git] / xdiff / xdiffi.c
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, write to the Free Software
17 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 *
19 * Davide Libenzi <davidel@xmailserver.org>
20 *
21 */
22
23 #include "xinclude.h"
24
25
26
27 #define XDL_MAX_COST_MIN 256
28 #define XDL_HEUR_MIN_COST 256
29 #define XDL_LINE_MAX (long)((1UL << (8 * sizeof(long) - 1)) - 1)
30 #define XDL_SNAKE_CNT 20
31 #define XDL_K_HEUR 4
32
33
34
35 typedef struct s_xdpsplit {
36 long i1, i2;
37 int min_lo, min_hi;
38 } xdpsplit_t;
39
40
41
42
43 static long xdl_split(unsigned long const *ha1, long off1, long lim1,
44 unsigned long const *ha2, long off2, long lim2,
45 long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
46 xdalgoenv_t *xenv);
47 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2);
48 static int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags);
49
50
51
52
53
54 /*
55 * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
56 * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
57 * the forward diagonal starting from (off1, off2) and the backward diagonal
58 * starting from (lim1, lim2). If the K values on the same diagonal crosses
59 * returns the furthest point of reach. We might end up having to expensive
60 * cases using this algorithm is full, so a little bit of heuristic is needed
61 * to cut the search and to return a suboptimal point.
62 */
63 static long xdl_split(unsigned long const *ha1, long off1, long lim1,
64 unsigned long const *ha2, long off2, long lim2,
65 long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
66 xdalgoenv_t *xenv) {
67 long dmin = off1 - lim2, dmax = lim1 - off2;
68 long fmid = off1 - off2, bmid = lim1 - lim2;
69 long odd = (fmid - bmid) & 1;
70 long fmin = fmid, fmax = fmid;
71 long bmin = bmid, bmax = bmid;
72 long ec, d, i1, i2, prev1, best, dd, v, k;
73
74 /*
75 * Set initial diagonal values for both forward and backward path.
76 */
77 kvdf[fmid] = off1;
78 kvdb[bmid] = lim1;
79
80 for (ec = 1;; ec++) {
81 int got_snake = 0;
82
83 /*
84 * We need to extent the diagonal "domain" by one. If the next
85 * values exits the box boundaries we need to change it in the
86 * opposite direction because (max - min) must be a power of two.
87 * Also we initialize the extenal K value to -1 so that we can
88 * avoid extra conditions check inside the core loop.
89 */
90 if (fmin > dmin)
91 kvdf[--fmin - 1] = -1;
92 else
93 ++fmin;
94 if (fmax < dmax)
95 kvdf[++fmax + 1] = -1;
96 else
97 --fmax;
98
99 for (d = fmax; d >= fmin; d -= 2) {
100 if (kvdf[d - 1] >= kvdf[d + 1])
101 i1 = kvdf[d - 1] + 1;
102 else
103 i1 = kvdf[d + 1];
104 prev1 = i1;
105 i2 = i1 - d;
106 for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
107 if (i1 - prev1 > xenv->snake_cnt)
108 got_snake = 1;
109 kvdf[d] = i1;
110 if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
111 spl->i1 = i1;
112 spl->i2 = i2;
113 spl->min_lo = spl->min_hi = 1;
114 return ec;
115 }
116 }
117
118 /*
119 * We need to extent the diagonal "domain" by one. If the next
120 * values exits the box boundaries we need to change it in the
121 * opposite direction because (max - min) must be a power of two.
122 * Also we initialize the extenal K value to -1 so that we can
123 * avoid extra conditions check inside the core loop.
124 */
125 if (bmin > dmin)
126 kvdb[--bmin - 1] = XDL_LINE_MAX;
127 else
128 ++bmin;
129 if (bmax < dmax)
130 kvdb[++bmax + 1] = XDL_LINE_MAX;
131 else
132 --bmax;
133
134 for (d = bmax; d >= bmin; d -= 2) {
135 if (kvdb[d - 1] < kvdb[d + 1])
136 i1 = kvdb[d - 1];
137 else
138 i1 = kvdb[d + 1] - 1;
139 prev1 = i1;
140 i2 = i1 - d;
141 for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
142 if (prev1 - i1 > xenv->snake_cnt)
143 got_snake = 1;
144 kvdb[d] = i1;
145 if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
146 spl->i1 = i1;
147 spl->i2 = i2;
148 spl->min_lo = spl->min_hi = 1;
149 return ec;
150 }
151 }
152
153 if (need_min)
154 continue;
155
156 /*
157 * If the edit cost is above the heuristic trigger and if
158 * we got a good snake, we sample current diagonals to see
159 * if some of the, have reached an "interesting" path. Our
160 * measure is a function of the distance from the diagonal
161 * corner (i1 + i2) penalized with the distance from the
162 * mid diagonal itself. If this value is above the current
163 * edit cost times a magic factor (XDL_K_HEUR) we consider
164 * it interesting.
165 */
166 if (got_snake && ec > xenv->heur_min) {
167 for (best = 0, d = fmax; d >= fmin; d -= 2) {
168 dd = d > fmid ? d - fmid: fmid - d;
169 i1 = kvdf[d];
170 i2 = i1 - d;
171 v = (i1 - off1) + (i2 - off2) - dd;
172
173 if (v > XDL_K_HEUR * ec && v > best &&
174 off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
175 off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
176 for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
177 if (k == xenv->snake_cnt) {
178 best = v;
179 spl->i1 = i1;
180 spl->i2 = i2;
181 break;
182 }
183 }
184 }
185 if (best > 0) {
186 spl->min_lo = 1;
187 spl->min_hi = 0;
188 return ec;
189 }
190
191 for (best = 0, d = bmax; d >= bmin; d -= 2) {
192 dd = d > bmid ? d - bmid: bmid - d;
193 i1 = kvdb[d];
194 i2 = i1 - d;
195 v = (lim1 - i1) + (lim2 - i2) - dd;
196
197 if (v > XDL_K_HEUR * ec && v > best &&
198 off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
199 off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
200 for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
201 if (k == xenv->snake_cnt - 1) {
202 best = v;
203 spl->i1 = i1;
204 spl->i2 = i2;
205 break;
206 }
207 }
208 }
209 if (best > 0) {
210 spl->min_lo = 0;
211 spl->min_hi = 1;
212 return ec;
213 }
214 }
215
216 /*
217 * Enough is enough. We spent too much time here and now we collect
218 * the furthest reaching path using the (i1 + i2) measure.
219 */
220 if (ec >= xenv->mxcost) {
221 long fbest, fbest1, bbest, bbest1;
222
223 fbest = fbest1 = -1;
224 for (d = fmax; d >= fmin; d -= 2) {
225 i1 = XDL_MIN(kvdf[d], lim1);
226 i2 = i1 - d;
227 if (lim2 < i2)
228 i1 = lim2 + d, i2 = lim2;
229 if (fbest < i1 + i2) {
230 fbest = i1 + i2;
231 fbest1 = i1;
232 }
233 }
234
235 bbest = bbest1 = XDL_LINE_MAX;
236 for (d = bmax; d >= bmin; d -= 2) {
237 i1 = XDL_MAX(off1, kvdb[d]);
238 i2 = i1 - d;
239 if (i2 < off2)
240 i1 = off2 + d, i2 = off2;
241 if (i1 + i2 < bbest) {
242 bbest = i1 + i2;
243 bbest1 = i1;
244 }
245 }
246
247 if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
248 spl->i1 = fbest1;
249 spl->i2 = fbest - fbest1;
250 spl->min_lo = 1;
251 spl->min_hi = 0;
252 } else {
253 spl->i1 = bbest1;
254 spl->i2 = bbest - bbest1;
255 spl->min_lo = 0;
256 spl->min_hi = 1;
257 }
258 return ec;
259 }
260 }
261
262 return -1;
263 }
264
265
266 /*
267 * Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
268 * the box splitting function. Note that the real job (marking changed lines)
269 * is done in the two boundary reaching checks.
270 */
271 int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
272 diffdata_t *dd2, long off2, long lim2,
273 long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
274 unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;
275
276 /*
277 * Shrink the box by walking through each diagonal snake (SW and NE).
278 */
279 for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
280 for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
281
282 /*
283 * If one dimension is empty, then all records on the other one must
284 * be obviously changed.
285 */
286 if (off1 == lim1) {
287 char *rchg2 = dd2->rchg;
288 long *rindex2 = dd2->rindex;
289
290 for (; off2 < lim2; off2++)
291 rchg2[rindex2[off2]] = 1;
292 } else if (off2 == lim2) {
293 char *rchg1 = dd1->rchg;
294 long *rindex1 = dd1->rindex;
295
296 for (; off1 < lim1; off1++)
297 rchg1[rindex1[off1]] = 1;
298 } else {
299 long ec;
300 xdpsplit_t spl;
301 spl.i1 = spl.i2 = 0;
302
303 /*
304 * Divide ...
305 */
306 if ((ec = xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
307 need_min, &spl, xenv)) < 0) {
308
309 return -1;
310 }
311
312 /*
313 * ... et Impera.
314 */
315 if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
316 kvdf, kvdb, spl.min_lo, xenv) < 0 ||
317 xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
318 kvdf, kvdb, spl.min_hi, xenv) < 0) {
319
320 return -1;
321 }
322 }
323
324 return 0;
325 }
326
327
328 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
329 xdfenv_t *xe) {
330 long ndiags;
331 long *kvd, *kvdf, *kvdb;
332 xdalgoenv_t xenv;
333 diffdata_t dd1, dd2;
334
335 if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
336
337 return -1;
338 }
339
340 /*
341 * Allocate and setup K vectors to be used by the differential algorithm.
342 * One is to store the forward path and one to store the backward path.
343 */
344 ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
345 if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
346
347 xdl_free_env(xe);
348 return -1;
349 }
350 kvdf = kvd;
351 kvdb = kvdf + ndiags;
352 kvdf += xe->xdf2.nreff + 1;
353 kvdb += xe->xdf2.nreff + 1;
354
355 xenv.mxcost = xdl_bogosqrt(ndiags);
356 if (xenv.mxcost < XDL_MAX_COST_MIN)
357 xenv.mxcost = XDL_MAX_COST_MIN;
358 xenv.snake_cnt = XDL_SNAKE_CNT;
359 xenv.heur_min = XDL_HEUR_MIN_COST;
360
361 dd1.nrec = xe->xdf1.nreff;
362 dd1.ha = xe->xdf1.ha;
363 dd1.rchg = xe->xdf1.rchg;
364 dd1.rindex = xe->xdf1.rindex;
365 dd2.nrec = xe->xdf2.nreff;
366 dd2.ha = xe->xdf2.ha;
367 dd2.rchg = xe->xdf2.rchg;
368 dd2.rindex = xe->xdf2.rindex;
369
370 if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
371 kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
372
373 xdl_free(kvd);
374 xdl_free_env(xe);
375 return -1;
376 }
377
378 xdl_free(kvd);
379
380 return 0;
381 }
382
383
384 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
385 xdchange_t *xch;
386
387 if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
388 return NULL;
389
390 xch->next = xscr;
391 xch->i1 = i1;
392 xch->i2 = i2;
393 xch->chg1 = chg1;
394 xch->chg2 = chg2;
395
396 return xch;
397 }
398
399
400 static int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
401 long ix, ixo, ixs, ixref, grpsiz, nrec = xdf->nrec;
402 char *rchg = xdf->rchg, *rchgo = xdfo->rchg;
403 xrecord_t **recs = xdf->recs;
404
405 /*
406 * This is the same of what GNU diff does. Move back and forward
407 * change groups for a consistent and pretty diff output. This also
408 * helps in finding joineable change groups and reduce the diff size.
409 */
410 for (ix = ixo = 0;;) {
411 /*
412 * Find the first changed line in the to-be-compacted file.
413 * We need to keep track of both indexes, so if we find a
414 * changed lines group on the other file, while scanning the
415 * to-be-compacted file, we need to skip it properly. Note
416 * that loops that are testing for changed lines on rchg* do
417 * not need index bounding since the array is prepared with
418 * a zero at position -1 and N.
419 */
420 for (; ix < nrec && !rchg[ix]; ix++)
421 while (rchgo[ixo++]);
422 if (ix == nrec)
423 break;
424
425 /*
426 * Record the start of a changed-group in the to-be-compacted file
427 * and find the end of it, on both to-be-compacted and other file
428 * indexes (ix and ixo).
429 */
430 ixs = ix;
431 for (ix++; rchg[ix]; ix++);
432 for (; rchgo[ixo]; ixo++);
433
434 do {
435 grpsiz = ix - ixs;
436
437 /*
438 * If the line before the current change group, is equal to
439 * the last line of the current change group, shift backward
440 * the group.
441 */
442 while (ixs > 0 && recs[ixs - 1]->ha == recs[ix - 1]->ha &&
443 xdl_recmatch(recs[ixs - 1]->ptr, recs[ixs - 1]->size, recs[ix - 1]->ptr, recs[ix - 1]->size, flags)) {
444 rchg[--ixs] = 1;
445 rchg[--ix] = 0;
446
447 /*
448 * This change might have joined two change groups,
449 * so we try to take this scenario in account by moving
450 * the start index accordingly (and so the other-file
451 * end-of-group index).
452 */
453 for (; rchg[ixs - 1]; ixs--);
454 while (rchgo[--ixo]);
455 }
456
457 /*
458 * Record the end-of-group position in case we are matched
459 * with a group of changes in the other file (that is, the
460 * change record before the enf-of-group index in the other
461 * file is set).
462 */
463 ixref = rchgo[ixo - 1] ? ix: nrec;
464
465 /*
466 * If the first line of the current change group, is equal to
467 * the line next of the current change group, shift forward
468 * the group.
469 */
470 while (ix < nrec && recs[ixs]->ha == recs[ix]->ha &&
471 xdl_recmatch(recs[ixs]->ptr, recs[ixs]->size, recs[ix]->ptr, recs[ix]->size, flags)) {
472 rchg[ixs++] = 0;
473 rchg[ix++] = 1;
474
475 /*
476 * This change might have joined two change groups,
477 * so we try to take this scenario in account by moving
478 * the start index accordingly (and so the other-file
479 * end-of-group index). Keep tracking the reference
480 * index in case we are shifting together with a
481 * corresponding group of changes in the other file.
482 */
483 for (; rchg[ix]; ix++);
484 while (rchgo[++ixo])
485 ixref = ix;
486 }
487 } while (grpsiz != ix - ixs);
488
489 /*
490 * Try to move back the possibly merged group of changes, to match
491 * the recorded postion in the other file.
492 */
493 while (ixref < ix) {
494 rchg[--ixs] = 1;
495 rchg[--ix] = 0;
496 while (rchgo[--ixo]);
497 }
498 }
499
500 return 0;
501 }
502
503
504 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
505 xdchange_t *cscr = NULL, *xch;
506 char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
507 long i1, i2, l1, l2;
508
509 /*
510 * Trivial. Collects "groups" of changes and creates an edit script.
511 */
512 for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
513 if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
514 for (l1 = i1; rchg1[i1 - 1]; i1--);
515 for (l2 = i2; rchg2[i2 - 1]; i2--);
516
517 if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
518 xdl_free_script(cscr);
519 return -1;
520 }
521 cscr = xch;
522 }
523
524 *xscr = cscr;
525
526 return 0;
527 }
528
529
530 void xdl_free_script(xdchange_t *xscr) {
531 xdchange_t *xch;
532
533 while ((xch = xscr) != NULL) {
534 xscr = xscr->next;
535 xdl_free(xch);
536 }
537 }
538
539
540 int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
541 xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
542 xdchange_t *xscr;
543 xdfenv_t xe;
544
545 if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
546
547 return -1;
548 }
549 if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
550 xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
551 xdl_build_script(&xe, &xscr) < 0) {
552
553 xdl_free_env(&xe);
554 return -1;
555 }
556 if (xscr) {
557 if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) {
558
559 xdl_free_script(xscr);
560 xdl_free_env(&xe);
561 return -1;
562 }
563 xdl_free_script(xscr);
564 }
565 xdl_free_env(&xe);
566
567 return 0;
568 }
569