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   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 /*
  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                 long ec;
 297                 xdpsplit_t spl;
 298                 spl.i1 = spl.i2 = 0;
 299
 300                 /*
 301                  * Divide ...
 302                  */
 303                 if ((ec = xdl_split(ha1, off1, lim1, ha2, off2, lim2, kvdf, kvdb,
 304                                     need_min, &spl, xenv)) < 0) {
 305
 306                         return -1;
 307                 }
 308
 309                 /*
 310                  * ... et Impera.
 311                  */
 312                 if (xdl_recs_cmp(dd1, off1, spl.i1, dd2, off2, spl.i2,
 313                                  kvdf, kvdb, spl.min_lo, xenv) < 0 ||
 314                     xdl_recs_cmp(dd1, spl.i1, lim1, dd2, spl.i2, lim2,
 315                                  kvdf, kvdb, spl.min_hi, xenv) < 0) {
 316
 317                         return -1;
 318                 }
 319         }
 320
 321         return 0;
 322 }
 323
 324
 325 int xdl_do_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 326                 xdfenv_t *xe) {
 327         long ndiags;
 328         long *kvd, *kvdf, *kvdb;
 329         xdalgoenv_t xenv;
 330         diffdata_t dd1, dd2;
 331
 332         if (xdl_prepare_env(mf1, mf2, xpp, xe) < 0) {
 333
 334                 return -1;
 335         }
 336
 337         /*
 338          * Allocate and setup K vectors to be used by the differential algorithm.
 339          * One is to store the forward path and one to store the backward path.
 340          */
 341         ndiags = xe->xdf1.nreff + xe->xdf2.nreff + 3;
 342         if (!(kvd = (long *) xdl_malloc((2 * ndiags + 2) * sizeof(long)))) {
 343
 344                 xdl_free_env(xe);
 345                 return -1;
 346         }
 347         kvdf = kvd;
 348         kvdb = kvdf + ndiags;
 349         kvdf += xe->xdf2.nreff + 1;
 350         kvdb += xe->xdf2.nreff + 1;
 351
 352         xenv.mxcost = xdl_bogosqrt(ndiags);
 353         if (xenv.mxcost < XDL_MAX_COST_MIN)
 354                 xenv.mxcost = XDL_MAX_COST_MIN;
 355         xenv.snake_cnt = XDL_SNAKE_CNT;
 356         xenv.heur_min = XDL_HEUR_MIN_COST;
 357
 358         dd1.nrec = xe->xdf1.nreff;
 359         dd1.ha = xe->xdf1.ha;
 360         dd1.rchg = xe->xdf1.rchg;
 361         dd1.rindex = xe->xdf1.rindex;
 362         dd2.nrec = xe->xdf2.nreff;
 363         dd2.ha = xe->xdf2.ha;
 364         dd2.rchg = xe->xdf2.rchg;
 365         dd2.rindex = xe->xdf2.rindex;
 366
 367         if (xdl_recs_cmp(&dd1, 0, dd1.nrec, &dd2, 0, dd2.nrec,
 368                          kvdf, kvdb, (xpp->flags & XDF_NEED_MINIMAL) != 0, &xenv) < 0) {
 369
 370                 xdl_free(kvd);
 371                 xdl_free_env(xe);
 372                 return -1;
 373         }
 374
 375         xdl_free(kvd);
 376
 377         return 0;
 378 }
 379
 380
 381 static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2) {
 382         xdchange_t *xch;
 383
 384         if (!(xch = (xdchange_t *) xdl_malloc(sizeof(xdchange_t))))
 385                 return NULL;
 386
 387         xch->next = xscr;
 388         xch->i1 = i1;
 389         xch->i2 = i2;
 390         xch->chg1 = chg1;
 391         xch->chg2 = chg2;
 392
 393         return xch;
 394 }
 395
 396
 397 int xdl_change_compact(xdfile_t *xdf, xdfile_t *xdfo, long flags) {
 398         long ix, ixo, ixs, ixref, grpsiz, nrec = xdf->nrec;
 399         char *rchg = xdf->rchg, *rchgo = xdfo->rchg;
 400         xrecord_t **recs = xdf->recs;
 401
 402         /*
 403          * This is the same of what GNU diff does. Move back and forward
 404          * change groups for a consistent and pretty diff output. This also
 405          * helps in finding joinable change groups and reduce the diff size.
 406          */
 407         for (ix = ixo = 0;;) {
 408                 /*
 409                  * Find the first changed line in the to-be-compacted file.
 410                  * We need to keep track of both indexes, so if we find a
 411                  * changed lines group on the other file, while scanning the
 412                  * to-be-compacted file, we need to skip it properly. Note
 413                  * that loops that are testing for changed lines on rchg* do
 414                  * not need index bounding since the array is prepared with
 415                  * a zero at position -1 and N.
 416                  */
 417                 for (; ix < nrec && !rchg[ix]; ix++)
 418                         while (rchgo[ixo++]);
 419                 if (ix == nrec)
 420                         break;
 421
 422                 /*
 423                  * Record the start of a changed-group in the to-be-compacted file
 424                  * and find the end of it, on both to-be-compacted and other file
 425                  * indexes (ix and ixo).
 426                  */
 427                 ixs = ix;
 428                 for (ix++; rchg[ix]; ix++);
 429                 for (; rchgo[ixo]; ixo++);
 430
 431                 do {
 432                         grpsiz = ix - ixs;
 433
 434                         /*
 435                          * If the line before the current change group, is equal to
 436                          * the last line of the current change group, shift backward
 437                          * the group.
 438                          */
 439                         while (ixs > 0 && recs[ixs - 1]->ha == recs[ix - 1]->ha &&
 440                                xdl_recmatch(recs[ixs - 1]->ptr, recs[ixs - 1]->size, recs[ix - 1]->ptr, recs[ix - 1]->size, flags)) {
 441                                 rchg[--ixs] = 1;
 442                                 rchg[--ix] = 0;
 443
 444                                 /*
 445                                  * This change might have joined two change groups,
 446                                  * so we try to take this scenario in account by moving
 447                                  * the start index accordingly (and so the other-file
 448                                  * end-of-group index).
 449                                  */
 450                                 for (; rchg[ixs - 1]; ixs--);
 451                                 while (rchgo[--ixo]);
 452                         }
 453
 454                         /*
 455                          * Record the end-of-group position in case we are matched
 456                          * with a group of changes in the other file (that is, the
 457                          * change record before the enf-of-group index in the other
 458                          * file is set).
 459                          */
 460                         ixref = rchgo[ixo - 1] ? ix: nrec;
 461
 462                         /*
 463                          * If the first line of the current change group, is equal to
 464                          * the line next of the current change group, shift forward
 465                          * the group.
 466                          */
 467                         while (ix < nrec && recs[ixs]->ha == recs[ix]->ha &&
 468                                xdl_recmatch(recs[ixs]->ptr, recs[ixs]->size, recs[ix]->ptr, recs[ix]->size, flags)) {
 469                                 rchg[ixs++] = 0;
 470                                 rchg[ix++] = 1;
 471
 472                                 /*
 473                                  * This change might have joined two change groups,
 474                                  * so we try to take this scenario in account by moving
 475                                  * the start index accordingly (and so the other-file
 476                                  * end-of-group index). Keep tracking the reference
 477                                  * index in case we are shifting together with a
 478                                  * corresponding group of changes in the other file.
 479                                  */
 480                                 for (; rchg[ix]; ix++);
 481                                 while (rchgo[++ixo])
 482                                         ixref = ix;
 483                         }
 484                 } while (grpsiz != ix - ixs);
 485
 486                 /*
 487                  * Try to move back the possibly merged group of changes, to match
 488                  * the recorded postion in the other file.
 489                  */
 490                 while (ixref < ix) {
 491                         rchg[--ixs] = 1;
 492                         rchg[--ix] = 0;
 493                         while (rchgo[--ixo]);
 494                 }
 495         }
 496
 497         return 0;
 498 }
 499
 500
 501 int xdl_build_script(xdfenv_t *xe, xdchange_t **xscr) {
 502         xdchange_t *cscr = NULL, *xch;
 503         char *rchg1 = xe->xdf1.rchg, *rchg2 = xe->xdf2.rchg;
 504         long i1, i2, l1, l2;
 505
 506         /*
 507          * Trivial. Collects "groups" of changes and creates an edit script.
 508          */
 509         for (i1 = xe->xdf1.nrec, i2 = xe->xdf2.nrec; i1 >= 0 || i2 >= 0; i1--, i2--)
 510                 if (rchg1[i1 - 1] || rchg2[i2 - 1]) {
 511                         for (l1 = i1; rchg1[i1 - 1]; i1--);
 512                         for (l2 = i2; rchg2[i2 - 1]; i2--);
 513
 514                         if (!(xch = xdl_add_change(cscr, i1, i2, l1 - i1, l2 - i2))) {
 515                                 xdl_free_script(cscr);
 516                                 return -1;
 517                         }
 518                         cscr = xch;
 519                 }
 520
 521         *xscr = cscr;
 522
 523         return 0;
 524 }
 525
 526
 527 void xdl_free_script(xdchange_t *xscr) {
 528         xdchange_t *xch;
 529
 530         while ((xch = xscr) != NULL) {
 531                 xscr = xscr->next;
 532                 xdl_free(xch);
 533         }
 534 }
 535
 536
 537 int xdl_diff(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
 538              xdemitconf_t const *xecfg, xdemitcb_t *ecb) {
 539         xdchange_t *xscr;
 540         xdfenv_t xe;
 541
 542         if (xdl_do_diff(mf1, mf2, xpp, &xe) < 0) {
 543
 544                 return -1;
 545         }
 546         if (xdl_change_compact(&xe.xdf1, &xe.xdf2, xpp->flags) < 0 ||
 547             xdl_change_compact(&xe.xdf2, &xe.xdf1, xpp->flags) < 0 ||
 548             xdl_build_script(&xe, &xscr) < 0) {
 549
 550                 xdl_free_env(&xe);
 551                 return -1;
 552         }
 553         if (xscr) {
 554                 if (xdl_emit_diff(&xe, xscr, ecb, xecfg) < 0) {
 555
 556                         xdl_free_script(xscr);
 557                         xdl_free_env(&xe);
 558                         return -1;
 559                 }
 560                 xdl_free_script(xscr);
 561         }
 562         xdl_free_env(&xe);
 563
 564         return 0;
 565 }