Merge branch 'js/merge-base'
[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 external 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 external 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 joinable 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