xdiff/xdiffi.c: fix warnings about possibly uninitialized variables
[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
49
50
51
52 /*
53  * See "An O(ND) Difference Algorithm and its Variations", by Eugene Myers.
54  * Basically considers a "box" (off1, off2, lim1, lim2) and scan from both
55  * the forward diagonal starting from (off1, off2) and the backward diagonal
56  * starting from (lim1, lim2). If the K values on the same diagonal crosses
57  * returns the furthest point of reach. We might end up having to expensive
58  * cases using this algorithm is full, so a little bit of heuristic is needed
59  * to cut the search and to return a suboptimal point.
60  */
61 static long xdl_split(unsigned long const *ha1, long off1, long lim1,
62                       unsigned long const *ha2, long off2, long lim2,
63                       long *kvdf, long *kvdb, int need_min, xdpsplit_t *spl,
64                       xdalgoenv_t *xenv) {
65         long dmin = off1 - lim2, dmax = lim1 - off2;
66         long fmid = off1 - off2, bmid = lim1 - lim2;
67         long odd = (fmid - bmid) & 1;
68         long fmin = fmid, fmax = fmid;
69         long bmin = bmid, bmax = bmid;
70         long ec, d, i1, i2, prev1, best, dd, v, k;
71
72         /*
73          * Set initial diagonal values for both forward and backward path.
74          */
75         kvdf[fmid] = off1;
76         kvdb[bmid] = lim1;
77
78         for (ec = 1;; ec++) {
79                 int got_snake = 0;
80
81                 /*
82                  * We need to extent the diagonal "domain" by one. If the next
83                  * values exits the box boundaries we need to change it in the
84                  * opposite direction because (max - min) must be a power of two.
85                  * Also we initialize the extenal K value to -1 so that we can
86                  * avoid extra conditions check inside the core loop.
87                  */
88                 if (fmin > dmin)
89                         kvdf[--fmin - 1] = -1;
90                 else
91                         ++fmin;
92                 if (fmax < dmax)
93                         kvdf[++fmax + 1] = -1;
94                 else
95                         --fmax;
96
97                 for (d = fmax; d >= fmin; d -= 2) {
98                         if (kvdf[d - 1] >= kvdf[d + 1])
99                                 i1 = kvdf[d - 1] + 1;
100                         else
101                                 i1 = kvdf[d + 1];
102                         prev1 = i1;
103                         i2 = i1 - d;
104                         for (; i1 < lim1 && i2 < lim2 && ha1[i1] == ha2[i2]; i1++, i2++);
105                         if (i1 - prev1 > xenv->snake_cnt)
106                                 got_snake = 1;
107                         kvdf[d] = i1;
108                         if (odd && bmin <= d && d <= bmax && kvdb[d] <= i1) {
109                                 spl->i1 = i1;
110                                 spl->i2 = i2;
111                                 spl->min_lo = spl->min_hi = 1;
112                                 return ec;
113                         }
114                 }
115
116                 /*
117                  * We need to extent the diagonal "domain" by one. If the next
118                  * values exits the box boundaries we need to change it in the
119                  * opposite direction because (max - min) must be a power of two.
120                  * Also we initialize the extenal K value to -1 so that we can
121                  * avoid extra conditions check inside the core loop.
122                  */
123                 if (bmin > dmin)
124                         kvdb[--bmin - 1] = XDL_LINE_MAX;
125                 else
126                         ++bmin;
127                 if (bmax < dmax)
128                         kvdb[++bmax + 1] = XDL_LINE_MAX;
129                 else
130                         --bmax;
131
132                 for (d = bmax; d >= bmin; d -= 2) {
133                         if (kvdb[d - 1] < kvdb[d + 1])
134                                 i1 = kvdb[d - 1];
135                         else
136                                 i1 = kvdb[d + 1] - 1;
137                         prev1 = i1;
138                         i2 = i1 - d;
139                         for (; i1 > off1 && i2 > off2 && ha1[i1 - 1] == ha2[i2 - 1]; i1--, i2--);
140                         if (prev1 - i1 > xenv->snake_cnt)
141                                 got_snake = 1;
142                         kvdb[d] = i1;
143                         if (!odd && fmin <= d && d <= fmax && i1 <= kvdf[d]) {
144                                 spl->i1 = i1;
145                                 spl->i2 = i2;
146                                 spl->min_lo = spl->min_hi = 1;
147                                 return ec;
148                         }
149                 }
150
151                 if (need_min)
152                         continue;
153
154                 /*
155                  * If the edit cost is above the heuristic trigger and if
156                  * we got a good snake, we sample current diagonals to see
157                  * if some of the, have reached an "interesting" path. Our
158                  * measure is a function of the distance from the diagonal
159                  * corner (i1 + i2) penalized with the distance from the
160                  * mid diagonal itself. If this value is above the current
161                  * edit cost times a magic factor (XDL_K_HEUR) we consider
162                  * it interesting.
163                  */
164                 if (got_snake && ec > xenv->heur_min) {
165                         for (best = 0, d = fmax; d >= fmin; d -= 2) {
166                                 dd = d > fmid ? d - fmid: fmid - d;
167                                 i1 = kvdf[d];
168                                 i2 = i1 - d;
169                                 v = (i1 - off1) + (i2 - off2) - dd;
170
171                                 if (v > XDL_K_HEUR * ec && v > best &&
172                                     off1 + xenv->snake_cnt <= i1 && i1 < lim1 &&
173                                     off2 + xenv->snake_cnt <= i2 && i2 < lim2) {
174                                         for (k = 1; ha1[i1 - k] == ha2[i2 - k]; k++)
175                                                 if (k == xenv->snake_cnt) {
176                                                         best = v;
177                                                         spl->i1 = i1;
178                                                         spl->i2 = i2;
179                                                         break;
180                                                 }
181                                 }
182                         }
183                         if (best > 0) {
184                                 spl->min_lo = 1;
185                                 spl->min_hi = 0;
186                                 return ec;
187                         }
188
189                         for (best = 0, d = bmax; d >= bmin; d -= 2) {
190                                 dd = d > bmid ? d - bmid: bmid - d;
191                                 i1 = kvdb[d];
192                                 i2 = i1 - d;
193                                 v = (lim1 - i1) + (lim2 - i2) - dd;
194
195                                 if (v > XDL_K_HEUR * ec && v > best &&
196                                     off1 < i1 && i1 <= lim1 - xenv->snake_cnt &&
197                                     off2 < i2 && i2 <= lim2 - xenv->snake_cnt) {
198                                         for (k = 0; ha1[i1 + k] == ha2[i2 + k]; k++)
199                                                 if (k == xenv->snake_cnt - 1) {
200                                                         best = v;
201                                                         spl->i1 = i1;
202                                                         spl->i2 = i2;
203                                                         break;
204                                                 }
205                                 }
206                         }
207                         if (best > 0) {
208                                 spl->min_lo = 0;
209                                 spl->min_hi = 1;
210                                 return ec;
211                         }
212                 }
213
214                 /*
215                  * Enough is enough. We spent too much time here and now we collect
216                  * the furthest reaching path using the (i1 + i2) measure.
217                  */
218                 if (ec >= xenv->mxcost) {
219                         long fbest, fbest1, bbest, bbest1;
220
221                         fbest = fbest1 = -1;
222                         for (d = fmax; d >= fmin; d -= 2) {
223                                 i1 = XDL_MIN(kvdf[d], lim1);
224                                 i2 = i1 - d;
225                                 if (lim2 < i2)
226                                         i1 = lim2 + d, i2 = lim2;
227                                 if (fbest < i1 + i2) {
228                                         fbest = i1 + i2;
229                                         fbest1 = i1;
230                                 }
231                         }
232
233                         bbest = bbest1 = XDL_LINE_MAX;
234                         for (d = bmax; d >= bmin; d -= 2) {
235                                 i1 = XDL_MAX(off1, kvdb[d]);
236                                 i2 = i1 - d;
237                                 if (i2 < off2)
238                                         i1 = off2 + d, i2 = off2;
239                                 if (i1 + i2 < bbest) {
240                                         bbest = i1 + i2;
241                                         bbest1 = i1;
242                                 }
243                         }
244
245                         if ((lim1 + lim2) - bbest < fbest - (off1 + off2)) {
246                                 spl->i1 = fbest1;
247                                 spl->i2 = fbest - fbest1;
248                                 spl->min_lo = 1;
249                                 spl->min_hi = 0;
250                         } else {
251                                 spl->i1 = bbest1;
252                                 spl->i2 = bbest - bbest1;
253                                 spl->min_lo = 0;
254                                 spl->min_hi = 1;
255                         }
256                         return ec;
257                 }
258         }
259
260         return -1;
261 }
262
263
264 /*
265  * Rule: "Divide et Impera". Recursively split the box in sub-boxes by calling
266  * the box splitting function. Note that the real job (marking changed lines)
267  * is done in the two boundary reaching checks.
268  */
269 int xdl_recs_cmp(diffdata_t *dd1, long off1, long lim1,
270                  diffdata_t *dd2, long off2, long lim2,
271                  long *kvdf, long *kvdb, int need_min, xdalgoenv_t *xenv) {
272         unsigned long const *ha1 = dd1->ha, *ha2 = dd2->ha;
273
274         /*
275          * Shrink the box by walking through each diagonal snake (SW and NE).
276          */
277         for (; off1 < lim1 && off2 < lim2 && ha1[off1] == ha2[off2]; off1++, off2++);
278         for (; off1 < lim1 && off2 < lim2 && ha1[lim1 - 1] == ha2[lim2 - 1]; lim1--, lim2--);
279
280         /*
281          * If one dimension is empty, then all records on the other one must
282          * be obviously changed.
283          */
284         if (off1 == lim1) {
285                 char *rchg2 = dd2->rchg;
286                 long *rindex2 = dd2->rindex;
287
288                 for (; off2 < lim2; off2++)
289                         rchg2[rindex2[off2]] = 1;
290         } else if (off2 == lim2) {
291                 char *rchg1 = dd1->rchg;
292                 long *rindex1 = dd1->rindex;
293
294                 for (; off1 < lim1; off1++)
295                         rchg1[rindex1[off1]] = 1;
296         } else {
297                 long ec;
298                 xdpsplit_t spl;
299                 spl.i1 = spl.i2 = 0;
300
301                 /*
302                  * Divide ...
303                  */
304                 if ((ec = xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
305                                     need_min, &spl, xenv)) < 0) {
306
307                         return -1;
308                 }
309
310                 /*
311                  * ... et Impera.
312                  */
313                 if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
314                                  kvdf, kvdb, spl.min_lo, xenv) < 0 ||
315                     xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
316                                  kvdf, kvdb, spl.min_hi, xenv) < 0) {
317
318                         return -1;
319                 }
320         }
321
322         return 0;
323 }
324
325
326 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
327                 xdfenv_t *xe) {
328         long ndiags;
329         long *kvd, *kvdf, *kvdb;
330         xdalgoenv_t xenv;
331         diffdata_t dd1, dd2;
332
333         if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
334
335                 return -1;
336         }
337
338         /*
339          * Allocate and setup K vectors to be used by the differential algorithm.
340          * One is to store the forward path and one to store the backward path.
341          */
342         ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
343         if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
344
345                 xdl_free_env(xe);
346                 return -1;
347         }
348         kvdf = kvd;
349         kvdb = kvdf + ndiags;
350         kvdf += xe->xdf2.nreff + 1;
351         kvdb += xe->xdf2.nreff + 1;
352
353         xenv.mxcost = xdl_bogosqrt(ndiags);
354         if (xenv.mxcost < XDL_MAX_COST_MIN)
355                 xenv.mxcost = XDL_MAX_COST_MIN;
356         xenv.snake_cnt = XDL_SNAKE_CNT;
357         xenv.heur_min = XDL_HEUR_MIN_COST;
358
359         dd1.nrec = xe->xdf1.nreff;
360         dd1.ha = xe->xdf1.ha;
361         dd1.rchg = xe->xdf1.rchg;
362         dd1.rindex = xe->xdf1.rindex;
363         dd2.nrec = xe->xdf2.nreff;
364         dd2.ha = xe->xdf2.ha;
365         dd2.rchg = xe->xdf2.rchg;
366         dd2.rindex = xe->xdf2.rindex;
367
368         if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
369                          kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
370
371                 xdl_free(kvd);
372                 xdl_free_env(xe);
373                 return -1;
374         }
375
376         xdl_free(kvd);
377
378         return 0;
379 }
380
381
382 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
383         xdchange_t *xch;
384
385         if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
386                 return NULL;
387
388         xch->next = xscr;
389         xch->i1 = i1;
390         xch->i2 = i2;
391         xch->chg1 = chg1;
392         xch->chg2 = chg2;
393
394         return xch;
395 }
396
397
398 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
399         xdchange_t *cscr = NULL, *xch;
400         char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
401         long i1, i2, l1, l2;
402
403         /*
404          * Trivial. Collects "groups" of changes and creates an edit script.
405          */
406         for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
407                 if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
408                         for (l1 = i1; rchg1[i1 - 1]; i1--);
409                         for (l2 = i2; rchg2[i2 - 1]; i2--);
410
411                         if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
412                                 xdl_free_script(cscr);
413                                 return -1;
414                         }
415                         cscr = xch;
416                 }
417
418         *xscr = cscr;
419
420         return 0;
421 }
422
423
424 void xdl_free_script(xdchange_t *xscr) {
425         xdchange_t *xch;
426
427         while ((xch = xscr) != NULL) {
428                 xscr = xscr->next;
429                 xdl_free(xch);
430         }
431 }
432
433
434 int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
435              xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
436         xdchange_t *xscr;
437         xdfenv_t xe;
438
439         if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
440
441                 return -1;
442         }
443
444         if (xdl_build_script(&xe, &xscr) < 0) {
445
446                 xdl_free_env(&xe);
447                 return -1;
448         }
449
450         if (xscr) {
451                 if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) {
452
453                         xdl_free_script(xscr);
454                         xdl_free_env(&xe);
455                         return -1;
456                 }
457
458                 xdl_free_script(xscr);
459         }
460
461         xdl_free_env(&xe);
462
463         return 0;
464 }
465