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 35typedef struct s_xdpsplit { 36 long i1, i2; 37 int min_lo, min_hi; 38} xdpsplit_t; 39 40 41 42 43static 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); 47static xdchange_t *xdl_add_change(xdchange_t *xscr, long i1, long i2, long chg1, long chg2); 48static 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 */ 63static 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 extenal 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 extenal 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 */ 271int 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 328int 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 384static 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 400static 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 joineable 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 504int 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 530void 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 540int 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