Merge branch 'cc/cherry-pick-ff'
[git] / xdiff / xmerge.c
1 /*
2  *  LibXDiff by Davide Libenzi ( File Differential Library )
3  *  Copyright (C) 2003-2006 Davide Libenzi, Johannes E. Schindelin
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 typedef struct s_xdmerge {
26         struct s_xdmerge *next;
27         /*
28          * 0 = conflict,
29          * 1 = no conflict, take first,
30          * 2 = no conflict, take second.
31          * 3 = no conflict, take both.
32          */
33         int mode;
34         /*
35          * These point at the respective postimages.  E.g. <i1,chg1> is
36          * how side #1 wants to change the common ancestor; if there is no
37          * overlap, lines before i1 in the postimage of side #1 appear
38          * in the merge result as a region touched by neither side.
39          */
40         long i1, i2;
41         long chg1, chg2;
42         /*
43          * These point at the preimage; of course there is just one
44          * preimage, that is from the shared common ancestor.
45          */
46         long i0;
47         long chg0;
48 } xdmerge_t;
49
50 static int xdl_append_merge(xdmerge_t **merge, int mode,
51                             long i0, long chg0,
52                             long i1, long chg1,
53                             long i2, long chg2)
54 {
55         xdmerge_t *m = *merge;
56         if (m && (i1 <= m->i1 + m->chg1 || i2 <= m->i2 + m->chg2)) {
57                 if (mode != m->mode)
58                         m->mode = 0;
59                 m->chg0 = i0 + chg0 - m->i0;
60                 m->chg1 = i1 + chg1 - m->i1;
61                 m->chg2 = i2 + chg2 - m->i2;
62         } else {
63                 m = xdl_malloc(sizeof(xdmerge_t));
64                 if (!m)
65                         return -1;
66                 m->next = NULL;
67                 m->mode = mode;
68                 m->i0 = i0;
69                 m->chg0 = chg0;
70                 m->i1 = i1;
71                 m->chg1 = chg1;
72                 m->i2 = i2;
73                 m->chg2 = chg2;
74                 if (*merge)
75                         (*merge)->next = m;
76                 *merge = m;
77         }
78         return 0;
79 }
80
81 static int xdl_cleanup_merge(xdmerge_t *c)
82 {
83         int count = 0;
84         xdmerge_t *next_c;
85
86         /* were there conflicts? */
87         for (; c; c = next_c) {
88                 if (c->mode == 0)
89                         count++;
90                 next_c = c->next;
91                 free(c);
92         }
93         return count;
94 }
95
96 static int xdl_merge_cmp_lines(xdfenv_t *xe1, int i1, xdfenv_t *xe2, int i2,
97                 int line_count, long flags)
98 {
99         int i;
100         xrecord_t **rec1 = xe1->xdf2.recs + i1;
101         xrecord_t **rec2 = xe2->xdf2.recs + i2;
102
103         for (i = 0; i < line_count; i++) {
104                 int result = xdl_recmatch(rec1[i]->ptr, rec1[i]->size,
105                         rec2[i]->ptr, rec2[i]->size, flags);
106                 if (!result)
107                         return -1;
108         }
109         return 0;
110 }
111
112 static int xdl_recs_copy_0(int use_orig, xdfenv_t *xe, int i, int count, int add_nl, char *dest)
113 {
114         xrecord_t **recs;
115         int size = 0;
116
117         recs = (use_orig ? xe->xdf1.recs : xe->xdf2.recs) + i;
118
119         if (count < 1)
120                 return 0;
121
122         for (i = 0; i < count; size += recs[i++]->size)
123                 if (dest)
124                         memcpy(dest + size, recs[i]->ptr, recs[i]->size);
125         if (add_nl) {
126                 i = recs[count - 1]->size;
127                 if (i == 0 || recs[count - 1]->ptr[i - 1] != '\n') {
128                         if (dest)
129                                 dest[size] = '\n';
130                         size++;
131                 }
132         }
133         return size;
134 }
135
136 static int xdl_recs_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
137 {
138         return xdl_recs_copy_0(0, xe, i, count, add_nl, dest);
139 }
140
141 static int xdl_orig_copy(xdfenv_t *xe, int i, int count, int add_nl, char *dest)
142 {
143         return xdl_recs_copy_0(1, xe, i, count, add_nl, dest);
144 }
145
146 static int fill_conflict_hunk(xdfenv_t *xe1, const char *name1,
147                               xdfenv_t *xe2, const char *name2,
148                               int size, int i, int style,
149                               xdmerge_t *m, char *dest, int marker_size)
150 {
151         int marker1_size = (name1 ? strlen(name1) + 1 : 0);
152         int marker2_size = (name2 ? strlen(name2) + 1 : 0);
153         int j;
154
155         if (marker_size <= 0)
156                 marker_size = DEFAULT_CONFLICT_MARKER_SIZE;
157
158         /* Before conflicting part */
159         size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
160                               dest ? dest + size : NULL);
161
162         if (!dest) {
163                 size += marker_size + 1 + marker1_size;
164         } else {
165                 for (j = 0; j < marker_size; j++)
166                         dest[size++] = '<';
167                 if (marker1_size) {
168                         dest[size] = ' ';
169                         memcpy(dest + size + 1, name1, marker1_size - 1);
170                         size += marker1_size;
171                 }
172                 dest[size++] = '\n';
173         }
174
175         /* Postimage from side #1 */
176         size += xdl_recs_copy(xe1, m->i1, m->chg1, 1,
177                               dest ? dest + size : NULL);
178
179         if (style == XDL_MERGE_DIFF3) {
180                 /* Shared preimage */
181                 if (!dest) {
182                         size += marker_size + 1;
183                 } else {
184                         for (j = 0; j < marker_size; j++)
185                                 dest[size++] = '|';
186                         dest[size++] = '\n';
187                 }
188                 size += xdl_orig_copy(xe1, m->i0, m->chg0, 1,
189                                       dest ? dest + size : NULL);
190         }
191
192         if (!dest) {
193                 size += marker_size + 1;
194         } else {
195                 for (j = 0; j < marker_size; j++)
196                         dest[size++] = '=';
197                 dest[size++] = '\n';
198         }
199
200         /* Postimage from side #2 */
201         size += xdl_recs_copy(xe2, m->i2, m->chg2, 1,
202                               dest ? dest + size : NULL);
203         if (!dest) {
204                 size += marker_size + 1 + marker2_size;
205         } else {
206                 for (j = 0; j < marker_size; j++)
207                         dest[size++] = '>';
208                 if (marker2_size) {
209                         dest[size] = ' ';
210                         memcpy(dest + size + 1, name2, marker2_size - 1);
211                         size += marker2_size;
212                 }
213                 dest[size++] = '\n';
214         }
215         return size;
216 }
217
218 static int xdl_fill_merge_buffer(xdfenv_t *xe1, const char *name1,
219                                  xdfenv_t *xe2, const char *name2,
220                                  int favor,
221                                  xdmerge_t *m, char *dest, int style,
222                                  int marker_size)
223 {
224         int size, i;
225
226         for (size = i = 0; m; m = m->next) {
227                 if (favor && !m->mode)
228                         m->mode = favor;
229
230                 if (m->mode == 0)
231                         size = fill_conflict_hunk(xe1, name1, xe2, name2,
232                                                   size, i, style, m, dest,
233                                                   marker_size);
234                 else if (m->mode & 3) {
235                         /* Before conflicting part */
236                         size += xdl_recs_copy(xe1, i, m->i1 - i, 0,
237                                               dest ? dest + size : NULL);
238                         /* Postimage from side #1 */
239                         if (m->mode & 1)
240                                 size += xdl_recs_copy(xe1, m->i1, m->chg1, 1,
241                                                       dest ? dest + size : NULL);
242                         /* Postimage from side #2 */
243                         if (m->mode & 2)
244                                 size += xdl_recs_copy(xe2, m->i2, m->chg2, 1,
245                                                       dest ? dest + size : NULL);
246                 } else
247                         continue;
248                 i = m->i1 + m->chg1;
249         }
250         size += xdl_recs_copy(xe1, i, xe1->xdf2.nrec - i, 0,
251                               dest ? dest + size : NULL);
252         return size;
253 }
254
255 /*
256  * Sometimes, changes are not quite identical, but differ in only a few
257  * lines. Try hard to show only these few lines as conflicting.
258  */
259 static int xdl_refine_conflicts(xdfenv_t *xe1, xdfenv_t *xe2, xdmerge_t *m,
260                 xpparam_t const *xpp)
261 {
262         for (; m; m = m->next) {
263                 mmfile_t t1, t2;
264                 xdfenv_t xe;
265                 xdchange_t *xscr, *x;
266                 int i1 = m->i1, i2 = m->i2;
267
268                 /* let's handle just the conflicts */
269                 if (m->mode)
270                         continue;
271
272                 /* no sense refining a conflict when one side is empty */
273                 if (m->chg1 == 0 || m->chg2 == 0)
274                         continue;
275
276                 /*
277                  * This probably does not work outside git, since
278                  * we have a very simple mmfile structure.
279                  */
280                 t1.ptr = (char *)xe1->xdf2.recs[m->i1]->ptr;
281                 t1.size = xe1->xdf2.recs[m->i1 + m->chg1 - 1]->ptr
282                         + xe1->xdf2.recs[m->i1 + m->chg1 - 1]->size - t1.ptr;
283                 t2.ptr = (char *)xe2->xdf2.recs[m->i2]->ptr;
284                 t2.size = xe2->xdf2.recs[m->i2 + m->chg2 - 1]->ptr
285                         + xe2->xdf2.recs[m->i2 + m->chg2 - 1]->size - t2.ptr;
286                 if (xdl_do_diff(&t1, &t2, xpp, &xe) < 0)
287                         return -1;
288                 if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
289                     xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
290                     xdl_build_script(&xe, &xscr) < 0) {
291                         xdl_free_env(&xe);
292                         return -1;
293                 }
294                 if (!xscr) {
295                         /* If this happens, the changes are identical. */
296                         xdl_free_env(&xe);
297                         m->mode = 4;
298                         continue;
299                 }
300                 x = xscr;
301                 m->i1 = xscr->i1 + i1;
302                 m->chg1 = xscr->chg1;
303                 m->i2 = xscr->i2 + i2;
304                 m->chg2 = xscr->chg2;
305                 while (xscr->next) {
306                         xdmerge_t *m2 = xdl_malloc(sizeof(xdmerge_t));
307                         if (!m2) {
308                                 xdl_free_env(&xe);
309                                 xdl_free_script(x);
310                                 return -1;
311                         }
312                         xscr = xscr->next;
313                         m2->next = m->next;
314                         m->next = m2;
315                         m = m2;
316                         m->mode = 0;
317                         m->i1 = xscr->i1 + i1;
318                         m->chg1 = xscr->chg1;
319                         m->i2 = xscr->i2 + i2;
320                         m->chg2 = xscr->chg2;
321                 }
322                 xdl_free_env(&xe);
323                 xdl_free_script(x);
324         }
325         return 0;
326 }
327
328 static int line_contains_alnum(const char *ptr, long size)
329 {
330         while (size--)
331                 if (isalnum(*(ptr++)))
332                         return 1;
333         return 0;
334 }
335
336 static int lines_contain_alnum(xdfenv_t *xe, int i, int chg)
337 {
338         for (; chg; chg--, i++)
339                 if (line_contains_alnum(xe->xdf2.recs[i]->ptr,
340                                 xe->xdf2.recs[i]->size))
341                         return 1;
342         return 0;
343 }
344
345 /*
346  * This function merges m and m->next, marking everything between those hunks
347  * as conflicting, too.
348  */
349 static void xdl_merge_two_conflicts(xdmerge_t *m)
350 {
351         xdmerge_t *next_m = m->next;
352         m->chg1 = next_m->i1 + next_m->chg1 - m->i1;
353         m->chg2 = next_m->i2 + next_m->chg2 - m->i2;
354         m->next = next_m->next;
355         free(next_m);
356 }
357
358 /*
359  * If there are less than 3 non-conflicting lines between conflicts,
360  * it appears simpler -- because it takes up less (or as many) lines --
361  * if the lines are moved into the conflicts.
362  */
363 static int xdl_simplify_non_conflicts(xdfenv_t *xe1, xdmerge_t *m,
364                                       int simplify_if_no_alnum)
365 {
366         int result = 0;
367
368         if (!m)
369                 return result;
370         for (;;) {
371                 xdmerge_t *next_m = m->next;
372                 int begin, end;
373
374                 if (!next_m)
375                         return result;
376
377                 begin = m->i1 + m->chg1;
378                 end = next_m->i1;
379
380                 if (m->mode != 0 || next_m->mode != 0 ||
381                     (end - begin > 3 &&
382                      (!simplify_if_no_alnum ||
383                       lines_contain_alnum(xe1, begin, end - begin)))) {
384                         m = next_m;
385                 } else {
386                         result++;
387                         xdl_merge_two_conflicts(m);
388                 }
389         }
390 }
391
392 /*
393  * level == 0: mark all overlapping changes as conflict
394  * level == 1: mark overlapping changes as conflict only if not identical
395  * level == 2: analyze non-identical changes for minimal conflict set
396  * level == 3: analyze non-identical changes for minimal conflict set, but
397  *             treat hunks not containing any letter or number as conflicting
398  *
399  * returns < 0 on error, == 0 for no conflicts, else number of conflicts
400  */
401 static int xdl_do_merge(xdfenv_t *xe1, xdchange_t *xscr1, const char *name1,
402                 xdfenv_t *xe2, xdchange_t *xscr2, const char *name2,
403                 xmparam_t const *xmp, mmbuffer_t *result) {
404         xdmerge_t *changes, *c;
405         xpparam_t const *xpp = &xmp->xpp;
406         int i0, i1, i2, chg0, chg1, chg2;
407         int level = xmp->level;
408         int style = xmp->style;
409         int favor = xmp->favor;
410
411         if (style == XDL_MERGE_DIFF3) {
412                 /*
413                  * "diff3 -m" output does not make sense for anything
414                  * more aggressive than XDL_MERGE_EAGER.
415                  */
416                 if (XDL_MERGE_EAGER < level)
417                         level = XDL_MERGE_EAGER;
418         }
419
420         c = changes = NULL;
421
422         while (xscr1 && xscr2) {
423                 if (!changes)
424                         changes = c;
425                 if (xscr1->i1 + xscr1->chg1 < xscr2->i1) {
426                         i0 = xscr1->i1;
427                         i1 = xscr1->i2;
428                         i2 = xscr2->i2 - xscr2->i1 + xscr1->i1;
429                         chg0 = xscr1->chg1;
430                         chg1 = xscr1->chg2;
431                         chg2 = xscr1->chg1;
432                         if (xdl_append_merge(&c, 1,
433                                              i0, chg0, i1, chg1, i2, chg2)) {
434                                 xdl_cleanup_merge(changes);
435                                 return -1;
436                         }
437                         xscr1 = xscr1->next;
438                         continue;
439                 }
440                 if (xscr2->i1 + xscr2->chg1 < xscr1->i1) {
441                         i0 = xscr2->i1;
442                         i1 = xscr1->i2 - xscr1->i1 + xscr2->i1;
443                         i2 = xscr2->i2;
444                         chg0 = xscr2->chg1;
445                         chg1 = xscr2->chg1;
446                         chg2 = xscr2->chg2;
447                         if (xdl_append_merge(&c, 2,
448                                              i0, chg0, i1, chg1, i2, chg2)) {
449                                 xdl_cleanup_merge(changes);
450                                 return -1;
451                         }
452                         xscr2 = xscr2->next;
453                         continue;
454                 }
455                 if (level == XDL_MERGE_MINIMAL || xscr1->i1 != xscr2->i1 ||
456                                 xscr1->chg1 != xscr2->chg1 ||
457                                 xscr1->chg2 != xscr2->chg2 ||
458                                 xdl_merge_cmp_lines(xe1, xscr1->i2,
459                                         xe2, xscr2->i2,
460                                         xscr1->chg2, xpp->flags)) {
461                         /* conflict */
462                         int off = xscr1->i1 - xscr2->i1;
463                         int ffo = off + xscr1->chg1 - xscr2->chg1;
464
465                         i0 = xscr1->i1;
466                         i1 = xscr1->i2;
467                         i2 = xscr2->i2;
468                         if (off > 0) {
469                                 i0 -= off;
470                                 i1 -= off;
471                         }
472                         else
473                                 i2 += off;
474                         chg0 = xscr1->i1 + xscr1->chg1 - i0;
475                         chg1 = xscr1->i2 + xscr1->chg2 - i1;
476                         chg2 = xscr2->i2 + xscr2->chg2 - i2;
477                         if (ffo < 0) {
478                                 chg0 -= ffo;
479                                 chg1 -= ffo;
480                         } else
481                                 chg2 += ffo;
482                         if (xdl_append_merge(&c, 0,
483                                              i0, chg0, i1, chg1, i2, chg2)) {
484                                 xdl_cleanup_merge(changes);
485                                 return -1;
486                         }
487                 }
488
489                 i1 = xscr1->i1 + xscr1->chg1;
490                 i2 = xscr2->i1 + xscr2->chg1;
491
492                 if (i1 >= i2)
493                         xscr2 = xscr2->next;
494                 if (i2 >= i1)
495                         xscr1 = xscr1->next;
496         }
497         while (xscr1) {
498                 if (!changes)
499                         changes = c;
500                 i0 = xscr1->i1;
501                 i1 = xscr1->i2;
502                 i2 = xscr1->i1 + xe2->xdf2.nrec - xe2->xdf1.nrec;
503                 chg0 = xscr1->chg1;
504                 chg1 = xscr1->chg2;
505                 chg2 = xscr1->chg1;
506                 if (xdl_append_merge(&c, 1,
507                                      i0, chg0, i1, chg1, i2, chg2)) {
508                         xdl_cleanup_merge(changes);
509                         return -1;
510                 }
511                 xscr1 = xscr1->next;
512         }
513         while (xscr2) {
514                 if (!changes)
515                         changes = c;
516                 i0 = xscr2->i1;
517                 i1 = xscr2->i1 + xe1->xdf2.nrec - xe1->xdf1.nrec;
518                 i2 = xscr2->i2;
519                 chg0 = xscr2->chg1;
520                 chg1 = xscr2->chg1;
521                 chg2 = xscr2->chg2;
522                 if (xdl_append_merge(&c, 2,
523                                      i0, chg0, i1, chg1, i2, chg2)) {
524                         xdl_cleanup_merge(changes);
525                         return -1;
526                 }
527                 xscr2 = xscr2->next;
528         }
529         if (!changes)
530                 changes = c;
531         /* refine conflicts */
532         if (XDL_MERGE_ZEALOUS <= level &&
533             (xdl_refine_conflicts(xe1, xe2, changes, xpp) < 0 ||
534              xdl_simplify_non_conflicts(xe1, changes,
535                                         XDL_MERGE_ZEALOUS < level) < 0)) {
536                 xdl_cleanup_merge(changes);
537                 return -1;
538         }
539         /* output */
540         if (result) {
541                 int marker_size = xmp->marker_size;
542                 int size = xdl_fill_merge_buffer(xe1, name1, xe2, name2,
543                                                  favor, changes, NULL, style,
544                                                  marker_size);
545                 result->ptr = xdl_malloc(size);
546                 if (!result->ptr) {
547                         xdl_cleanup_merge(changes);
548                         return -1;
549                 }
550                 result->size = size;
551                 xdl_fill_merge_buffer(xe1, name1, xe2, name2, favor, changes,
552                                       result->ptr, style, marker_size);
553         }
554         return xdl_cleanup_merge(changes);
555 }
556
557 int xdl_merge(mmfile_t *orig, mmfile_t *mf1, const char *name1,
558                 mmfile_t *mf2, const char *name2,
559                 xmparam_t const *xmp, mmbuffer_t *result) {
560         xdchange_t *xscr1, *xscr2;
561         xdfenv_t xe1, xe2;
562         int status;
563         xpparam_t const *xpp = &xmp->xpp;
564
565         result->ptr = NULL;
566         result->size = 0;
567
568         if (xdl_do_diff(orig, mf1, xpp, &xe1) < 0 ||
569                         xdl_do_diff(orig, mf2, xpp, &xe2) < 0) {
570                 return -1;
571         }
572         if (xdl_change_compact(&xe1.xdf1, &xe1.xdf2, xpp->flags) < 0 ||
573             xdl_change_compact(&xe1.xdf2, &xe1.xdf1, xpp->flags) < 0 ||
574             xdl_build_script(&xe1, &xscr1) < 0) {
575                 xdl_free_env(&xe1);
576                 return -1;
577         }
578         if (xdl_change_compact(&xe2.xdf1, &xe2.xdf2, xpp->flags) < 0 ||
579             xdl_change_compact(&xe2.xdf2, &xe2.xdf1, xpp->flags) < 0 ||
580             xdl_build_script(&xe2, &xscr2) < 0) {
581                 xdl_free_env(&xe2);
582                 return -1;
583         }
584         status = 0;
585         if (!xscr1) {
586                 result->ptr = xdl_malloc(mf2->size);
587                 memcpy(result->ptr, mf2->ptr, mf2->size);
588                 result->size = mf2->size;
589         } else if (!xscr2) {
590                 result->ptr = xdl_malloc(mf1->size);
591                 memcpy(result->ptr, mf1->ptr, mf1->size);
592                 result->size = mf1->size;
593         } else {
594                 status = xdl_do_merge(&xe1, xscr1, name1,
595                                       &xe2, xscr2, name2,
596                                       xmp, result);
597         }
598         xdl_free_script(xscr1);
599         xdl_free_script(xscr2);
600
601         xdl_free_env(&xe1);
602         xdl_free_env(&xe2);
603
604         return status;
605 }