Merge branch 'jc/checkout-m-twoway'
[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 << (CHAR_BIT * 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
49
50
51
52
53 /*
54  * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
55  * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
56  * the forward diagonal starting from (off1, off2) and the backward diagonal
57  * starting from (lim1, lim2). If the K values on the same diagonal crosses
58  * returns the furthest point of reach. We might end up having to expensive
59  * cases using this algorithm is full, so a little bit of heuristic is needed
60  * to cut the search and to return a suboptimal point.
61  */
62 static long xdl_split(unsigned long const *ha1, long off1, long lim1,
63                       unsigned long const *ha2, long off2, long lim2,
64                       long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
65                       xdalgoenv_t *xenv) {
66         long dmin = off1 - lim2, dmax = lim1 - off2;
67         long fmid = off1 - off2, bmid = lim1 - lim2;
68         long odd = (fmid - bmid) & 1;
69         long fmin = fmid, fmax = fmid;
70         long bmin = bmid, bmax = bmid;
71         long ec, d, i1, i2, prev1, best, dd, v, k;
72
73         /*
74          * Set initial diagonal values for both forward and backward path.
75          */
76         kvdf[fmid] = off1;
77         kvdb[bmid] = lim1;
78
79         for (ec = 1;; ec++) {
80                 int got_snake = 0;
81
82                 /*
83                  * We need to extent the diagonal "domain" by one. If the next
84                  * values exits the box boundaries we need to change it in the
85                  * opposite direction because (max - min) must be a power of two.
86                  * Also we initialize the external K value to -1 so that we can
87                  * avoid extra conditions check inside the core loop.
88                  */
89                 if (fmin > dmin)
90                         kvdf[--fmin - 1] = -1;
91                 else
92                         ++fmin;
93                 if (fmax < dmax)
94                         kvdf[++fmax + 1] = -1;
95                 else
96                         --fmax;
97
98                 for (d = fmax; d >= fmin; d -= 2) {
99                         if (kvdf[d - 1] >= kvdf[d + 1])
100                                 i1 = kvdf[d - 1] + 1;
101                         else
102                                 i1 = kvdf[d + 1];
103                         prev1 = i1;
104                         i2 = i1 - d;
105                         for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
106                         if (i1 - prev1 > xenv->snake_cnt)
107                                 got_snake = 1;
108                         kvdf[d] = i1;
109                         if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
110                                 spl->i1 = i1;
111                                 spl->i2 = i2;
112                                 spl->min_lo = spl->min_hi = 1;
113                                 return ec;
114                         }
115                 }
116
117                 /*
118                  * We need to extent the diagonal "domain" by one. If the next
119                  * values exits the box boundaries we need to change it in the
120                  * opposite direction because (max - min) must be a power of two.
121                  * Also we initialize the external K value to -1 so that we can
122                  * avoid extra conditions check inside the core loop.
123                  */
124                 if (bmin > dmin)
125                         kvdb[--bmin - 1] = XDL_LINE_MAX;
126                 else
127                         ++bmin;
128                 if (bmax < dmax)
129                         kvdb[++bmax + 1] = XDL_LINE_MAX;
130                 else
131                         --bmax;
132
133                 for (d = bmax; d >= bmin; d -= 2) {
134                         if (kvdb[d - 1] < kvdb[d + 1])
135                                 i1 = kvdb[d - 1];
136                         else
137                                 i1 = kvdb[d + 1] - 1;
138                         prev1 = i1;
139                         i2 = i1 - d;
140                         for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
141                         if (prev1 - i1 > xenv->snake_cnt)
142                                 got_snake = 1;
143                         kvdb[d] = i1;
144                         if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
145                                 spl->i1 = i1;
146                                 spl->i2 = i2;
147                                 spl->min_lo = spl->min_hi = 1;
148                                 return ec;
149                         }
150                 }
151
152                 if (need_min)
153                         continue;
154
155                 /*
156                  * If the edit cost is above the heuristic trigger and if
157                  * we got a good snake, we sample current diagonals to see
158                  * if some of the, have reached an "interesting" path. Our
159                  * measure is a function of the distance from the diagonal
160                  * corner (i1 + i2) penalized with the distance from the
161                  * mid diagonal itself. If this value is above the current
162                  * edit cost times a magic factor (XDL_K_HEUR) we consider
163                  * it interesting.
164                  */
165                 if (got_snake && ec > xenv->heur_min) {
166                         for (best = 0, d = fmax; d >= fmin; d -= 2) {
167                                 dd = d > fmid ? d - fmid: fmid - d;
168                                 i1 = kvdf[d];
169                                 i2 = i1 - d;
170                                 v = (i1 - off1) + (i2 - off2) - dd;
171
172                                 if (v > XDL_K_HEUR * ec && v > best &&
173                                     off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
174                                     off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
175                                         for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
176                                                 if (k == xenv->snake_cnt) {
177                                                         best = v;
178                                                         spl->i1 = i1;
179                                                         spl->i2 = i2;
180                                                         break;
181                                                 }
182                                 }
183                         }
184                         if (best > 0) {
185                                 spl->min_lo = 1;
186                                 spl->min_hi = 0;
187                                 return ec;
188                         }
189
190                         for (best = 0, d = bmax; d >= bmin; d -= 2) {
191                                 dd = d > bmid ? d - bmid: bmid - d;
192                                 i1 = kvdb[d];
193                                 i2 = i1 - d;
194                                 v = (lim1 - i1) + (lim2 - i2) - dd;
195
196                                 if (v > XDL_K_HEUR * ec && v > best &&
197                                     off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
198                                     off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
199                                         for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
200                                                 if (k == xenv->snake_cnt - 1) {
201                                                         best = v;
202                                                         spl->i1 = i1;
203                                                         spl->i2 = i2;
204                                                         break;
205                                                 }
206                                 }
207                         }
208                         if (best > 0) {
209                                 spl->min_lo = 0;
210                                 spl->min_hi = 1;
211                                 return ec;
212                         }
213                 }
214
215                 /*
216                  * Enough is enough. We spent too much time here and now we collect
217                  * the furthest reaching path using the (i1 + i2) measure.
218                  */
219                 if (ec >= xenv->mxcost) {
220                         long fbest, fbest1, bbest, bbest1;
221
222                         fbest = fbest1 = -1;
223                         for (d = fmax; d >= fmin; d -= 2) {
224                                 i1 = XDL_MIN(kvdf[d], lim1);
225                                 i2 = i1 - d;
226                                 if (lim2 < i2)
227                                         i1 = lim2 + d, i2 = lim2;
228                                 if (fbest < i1 + i2) {
229                                         fbest = i1 + i2;
230                                         fbest1 = i1;
231                                 }
232                         }
233
234                         bbest = bbest1 = XDL_LINE_MAX;
235                         for (d = bmax; d >= bmin; d -= 2) {
236                                 i1 = XDL_MAX(off1, kvdb[d]);
237                                 i2 = i1 - d;
238                                 if (i2 < off2)
239                                         i1 = off2 + d, i2 = off2;
240                                 if (i1 + i2 < bbest) {
241                                         bbest = i1 + i2;
242                                         bbest1 = i1;
243                                 }
244                         }
245
246                         if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
247                                 spl->i1 = fbest1;
248                                 spl->i2 = fbest - fbest1;
249                                 spl->min_lo = 1;
250                                 spl->min_hi = 0;
251                         } else {
252                                 spl->i1 = bbest1;
253                                 spl->i2 = bbest - bbest1;
254                                 spl->min_lo = 0;
255                                 spl->min_hi = 1;
256                         }
257                         return ec;
258                 }
259         }
260 }
261
262
263 /*
264  * Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
265  * the box splitting function. Note that the real job (marking changed lines)
266  * is done in the two boundary reaching checks.
267  */
268 int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
269                  diffdata_t *dd2, long off2, long lim2,
270                  long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
271         unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;
272
273         /*
274          * Shrink the box by walking through each diagonal snake (SW and NE).
275          */
276         for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
277         for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
278
279         /*
280          * If one dimension is empty, then all records on the other one must
281          * be obviously changed.
282          */
283         if (off1 == lim1) {
284                 char *rchg2 = dd2->rchg;
285                 long *rindex2 = dd2->rindex;
286
287                 for (; off2 < lim2; off2++)
288                         rchg2[rindex2[off2]] = 1;
289         } else if (off2 == lim2) {
290                 char *rchg1 = dd1->rchg;
291                 long *rindex1 = dd1->rindex;
292
293                 for (; off1 < lim1; off1++)
294                         rchg1[rindex1[off1]] = 1;
295         } else {
296                 xdpsplit_t spl;
297                 spl.i1 = spl.i2 = 0;
298
299                 /*
300                  * Divide ...
301                  */
302                 if (xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
303                               need_min, &spl, xenv) < 0) {
304
305                         return -1;
306                 }
307
308                 /*
309                  * ... et Impera.
310                  */
311                 if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
312                                  kvdf, kvdb, spl.min_lo, xenv) < 0 ||
313                     xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
314                                  kvdf, kvdb, spl.min_hi, xenv) < 0) {
315
316                         return -1;
317                 }
318         }
319
320         return 0;
321 }
322
323
324 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
325                 xdfenv_t *xe) {
326         long ndiags;
327         long *kvd, *kvdf, *kvdb;
328         xdalgoenv_t xenv;
329         diffdata_t dd1, dd2;
330
331         if (xpp->flags & XDF_PATIENCE_DIFF)
332                 return xdl_do_patience_diff(mf1, mf2, xpp, xe);
333
334         if (xpp->flags & XDF_HISTOGRAM_DIFF)
335                 return xdl_do_histogram_diff(mf1, mf2, xpp, xe);
336
337         if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
338
339                 return -1;
340         }
341
342         /*
343          * Allocate and setup K vectors to be used by the differential algorithm.
344          * One is to store the forward path and one to store the backward path.
345          */
346         ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
347         if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
348
349                 xdl_free_env(xe);
350                 return -1;
351         }
352         kvdf = kvd;
353         kvdb = kvdf + ndiags;
354         kvdf += xe->xdf2.nreff + 1;
355         kvdb += xe->xdf2.nreff + 1;
356
357         xenv.mxcost = xdl_bogosqrt(ndiags);
358         if (xenv.mxcost < XDL_MAX_COST_MIN)
359                 xenv.mxcost = XDL_MAX_COST_MIN;
360         xenv.snake_cnt = XDL_SNAKE_CNT;
361         xenv.heur_min = XDL_HEUR_MIN_COST;
362
363         dd1.nrec = xe->xdf1.nreff;
364         dd1.ha = xe->xdf1.ha;
365         dd1.rchg = xe->xdf1.rchg;
366         dd1.rindex = xe->xdf1.rindex;
367         dd2.nrec = xe->xdf2.nreff;
368         dd2.ha = xe->xdf2.ha;
369         dd2.rchg = xe->xdf2.rchg;
370         dd2.rindex = xe->xdf2.rindex;
371
372         if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
373                          kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
374
375                 xdl_free(kvd);
376                 xdl_free_env(xe);
377                 return -1;
378         }
379
380         xdl_free(kvd);
381
382         return 0;
383 }
384
385
386 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
387         xdchange_t *xch;
388
389         if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
390                 return NULL;
391
392         xch->next = xscr;
393         xch->i1 = i1;
394         xch->i2 = i2;
395         xch->chg1 = chg1;
396         xch->chg2 = chg2;
397
398         return xch;
399 }
400
401
402 int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
403         long ix, ixo, ixs, ixref, grpsiz, nrec = xdf->nrec;
404         char *rchg = xdf->rchg, *rchgo = xdfo->rchg;
405         xrecord_t **recs = xdf->recs;
406
407         /*
408          * This is the same of what GNU diff does. Move back and forward
409          * change groups for a consistent and pretty diff output. This also
410          * helps in finding joinable change groups and reduce the diff size.
411          */
412         for (ix = ixo = 0;;) {
413                 /*
414                  * Find the first changed line in the to-be-compacted file.
415                  * We need to keep track of both indexes, so if we find a
416                  * changed lines group on the other file, while scanning the
417                  * to-be-compacted file, we need to skip it properly. Note
418                  * that loops that are testing for changed lines on rchg* do
419                  * not need index bounding since the array is prepared with
420                  * a zero at position -1 and N.
421                  */
422                 for (; ix < nrec && !rchg[ix]; ix++)
423                         while (rchgo[ixo++]);
424                 if (ix == nrec)
425                         break;
426
427                 /*
428                  * Record the start of a changed-group in the to-be-compacted file
429                  * and find the end of it, on both to-be-compacted and other file
430                  * indexes (ix and ixo).
431                  */
432                 ixs = ix;
433                 for (ix++; rchg[ix]; ix++);
434                 for (; rchgo[ixo]; ixo++);
435
436                 do {
437                         grpsiz = ix - ixs;
438
439                         /*
440                          * If the line before the current change group, is equal to
441                          * the last line of the current change group, shift backward
442                          * the group.
443                          */
444                         while (ixs > 0 && recs[ixs - 1]->ha == recs[ix - 1]->ha &&
445                                xdl_recmatch(recs[ixs - 1]->ptr, recs[ixs - 1]->size, recs[ix - 1]->ptr, recs[ix - 1]->size, flags)) {
446                                 rchg[--ixs] = 1;
447                                 rchg[--ix] = 0;
448
449                                 /*
450                                  * This change might have joined two change groups,
451                                  * so we try to take this scenario in account by moving
452                                  * the start index accordingly (and so the other-file
453                                  * end-of-group index).
454                                  */
455                                 for (; rchg[ixs - 1]; ixs--);
456                                 while (rchgo[--ixo]);
457                         }
458
459                         /*
460                          * Record the end-of-group position in case we are matched
461                          * with a group of changes in the other file (that is, the
462                          * change record before the end-of-group index in the other
463                          * file is set).
464                          */
465                         ixref = rchgo[ixo - 1] ? ix: nrec;
466
467                         /*
468                          * If the first line of the current change group, is equal to
469                          * the line next of the current change group, shift forward
470                          * the group.
471                          */
472                         while (ix < nrec && recs[ixs]->ha == recs[ix]->ha &&
473                                xdl_recmatch(recs[ixs]->ptr, recs[ixs]->size, recs[ix]->ptr, recs[ix]->size, flags)) {
474                                 rchg[ixs++] = 0;
475                                 rchg[ix++] = 1;
476
477                                 /*
478                                  * This change might have joined two change groups,
479                                  * so we try to take this scenario in account by moving
480                                  * the start index accordingly (and so the other-file
481                                  * end-of-group index). Keep tracking the reference
482                                  * index in case we are shifting together with a
483                                  * corresponding group of changes in the other file.
484                                  */
485                                 for (; rchg[ix]; ix++);
486                                 while (rchgo[++ixo])
487                                         ixref = ix;
488                         }
489                 } while (grpsiz != ix - ixs);
490
491                 /*
492                  * Try to move back the possibly merged group of changes, to match
493                  * the recorded postion in the other file.
494                  */
495                 while (ixref < ix) {
496                         rchg[--ixs] = 1;
497                         rchg[--ix] = 0;
498                         while (rchgo[--ixo]);
499                 }
500         }
501
502         return 0;
503 }
504
505
506 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
507         xdchange_t *cscr = NULL, *xch;
508         char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
509         long i1, i2, l1, l2;
510
511         /*
512          * Trivial. Collects "groups" of changes and creates an edit script.
513          */
514         for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
515                 if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
516                         for (l1 = i1; rchg1[i1 - 1]; i1--);
517                         for (l2 = i2; rchg2[i2 - 1]; i2--);
518
519                         if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
520                                 xdl_free_script(cscr);
521                                 return -1;
522                         }
523                         cscr = xch;
524                 }
525
526         *xscr = cscr;
527
528         return 0;
529 }
530
531
532 void xdl_free_script(xdchange_t *xscr) {
533         xdchange_t *xch;
534
535         while ((xch = xscr) != NULL) {
536                 xscr = xscr->next;
537                 xdl_free(xch);
538         }
539 }
540
541
542 int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
543              xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
544         xdchange_t *xscr;
545         xdfenv_t xe;
546         emit_func_t ef = xecfg->emit_func ?
547                 (emit_func_t)xecfg->emit_func : xdl_emit_diff;
548
549         if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
550
551                 return -1;
552         }
553         if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
554             xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
555             xdl_build_script(&xe, &xscr) < 0) {
556
557                 xdl_free_env(&xe);
558                 return -1;
559         }
560         if (xscr) {
561                 if (ef(&xe, xscr, ecb, xecfg) < 0) {
562
563                         xdl_free_script(xscr);
564                         xdl_free_env(&xe);
565                         return -1;
566                 }
567                 xdl_free_script(xscr);
568         }
569         xdl_free_env(&xe);
570
571         return 0;
572 }