diffcore-rename.c

   1 /*
   2  * Copyright (C) 2005 Junio C Hamano
   3  */
   4 #include "cache.h"
   5 #include "diff.h"
   6 #include "diffcore.h"
   7 #include "hash.h"
   8
   9 /* Table of rename/copy destinations */
  10
  11 static struct diff_rename_dst {
  12         struct diff_filespec *two;
  13         struct diff_filepair *pair;
  14 } *rename_dst;
  15 static int rename_dst_nr, rename_dst_alloc;
  16
  17 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
  18                                                  int insert_ok)
  19 {
  20         int first, last;
  21
  22         first = 0;
  23         last = rename_dst_nr;
  24         while (last > first) {
  25                 int next = (last + first) >> 1;
  26                 struct diff_rename_dst *dst = &(rename_dst[next]);
  27                 int cmp = strcmp(two->path, dst->two->path);
  28                 if (!cmp)
  29                         return dst;
  30                 if (cmp < 0) {
  31                         last = next;
  32                         continue;
  33                 }
  34                 first = next+1;
  35         }
  36         /* not found */
  37         if (!insert_ok)
  38                 return NULL;
  39         /* insert to make it at "first" */
  40         if (rename_dst_alloc <= rename_dst_nr) {
  41                 rename_dst_alloc = alloc_nr(rename_dst_alloc);
  42                 rename_dst = xrealloc(rename_dst,
  43                                       rename_dst_alloc * sizeof(*rename_dst));
  44         }
  45         rename_dst_nr++;
  46         if (first < rename_dst_nr)
  47                 memmove(rename_dst + first + 1, rename_dst + first,
  48                         (rename_dst_nr - first - 1) * sizeof(*rename_dst));
  49         rename_dst[first].two = alloc_filespec(two->path);
  50         fill_filespec(rename_dst[first].two, two->sha1, two->mode);
  51         rename_dst[first].pair = NULL;
  52         return &(rename_dst[first]);
  53 }
  54
  55 /* Table of rename/copy src files */
  56 static struct diff_rename_src {
  57         struct diff_filespec *one;
  58         unsigned short score; /* to remember the break score */
  59 } *rename_src;
  60 static int rename_src_nr, rename_src_alloc;
  61
  62 static struct diff_rename_src *register_rename_src(struct diff_filespec *one,
  63                                                    unsigned short score)
  64 {
  65         int first, last;
  66
  67         first = 0;
  68         last = rename_src_nr;
  69         while (last > first) {
  70                 int next = (last + first) >> 1;
  71                 struct diff_rename_src *src = &(rename_src[next]);
  72                 int cmp = strcmp(one->path, src->one->path);
  73                 if (!cmp)
  74                         return src;
  75                 if (cmp < 0) {
  76                         last = next;
  77                         continue;
  78                 }
  79                 first = next+1;
  80         }
  81
  82         /* insert to make it at "first" */
  83         if (rename_src_alloc <= rename_src_nr) {
  84                 rename_src_alloc = alloc_nr(rename_src_alloc);
  85                 rename_src = xrealloc(rename_src,
  86                                       rename_src_alloc * sizeof(*rename_src));
  87         }
  88         rename_src_nr++;
  89         if (first < rename_src_nr)
  90                 memmove(rename_src + first + 1, rename_src + first,
  91                         (rename_src_nr - first - 1) * sizeof(*rename_src));
  92         rename_src[first].one = one;
  93         rename_src[first].score = score;
  94         return &(rename_src[first]);
  95 }
  96
  97 static int basename_same(struct diff_filespec *src, struct diff_filespec *dst)
  98 {
  99         int src_len = strlen(src->path), dst_len = strlen(dst->path);
 100         while (src_len && dst_len) {
 101                 char c1 = src->path[--src_len];
 102                 char c2 = dst->path[--dst_len];
 103                 if (c1 != c2)
 104                         return 0;
 105                 if (c1 == '/')
 106                         return 1;
 107         }
 108         return (!src_len || src->path[src_len - 1] == '/') &&
 109                 (!dst_len || dst->path[dst_len - 1] == '/');
 110 }
 111
 112 struct diff_score {
 113         int src; /* index in rename_src */
 114         int dst; /* index in rename_dst */
 115         unsigned short score;
 116         short name_score;
 117 };
 118
 119 static int estimate_similarity(struct diff_filespec *src,
 120                                struct diff_filespec *dst,
 121                                int minimum_score)
 122 {
 123         /* src points at a file that existed in the original tree (or
 124          * optionally a file in the destination tree) and dst points
 125          * at a newly created file.  They may be quite similar, in which
 126          * case we want to say src is renamed to dst or src is copied into
 127          * dst, and then some edit has been applied to dst.
 128          *
 129          * Compare them and return how similar they are, representing
 130          * the score as an integer between 0 and MAX_SCORE.
 131          *
 132          * When there is an exact match, it is considered a better
 133          * match than anything else; the destination does not even
 134          * call into this function in that case.
 135          */
 136         unsigned long max_size, delta_size, base_size, src_copied, literal_added;
 137         unsigned long delta_limit;
 138         int score;
 139
 140         /* We deal only with regular files.  Symlink renames are handled
 141          * only when they are exact matches --- in other words, no edits
 142          * after renaming.
 143          */
 144         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
 145                 return 0;
 146
 147         /*
 148          * Need to check that source and destination sizes are
 149          * filled in before comparing them.
 150          *
 151          * If we already have "cnt_data" filled in, we know it's
 152          * all good (avoid checking the size for zero, as that
 153          * is a possible size - we really should have a flag to
 154          * say whether the size is valid or not!)
 155          */
 156         if (!src->cnt_data && diff_populate_filespec(src, 1))
 157                 return 0;
 158         if (!dst->cnt_data && diff_populate_filespec(dst, 1))
 159                 return 0;
 160
 161         max_size = ((src->size > dst->size) ? src->size : dst->size);
 162         base_size = ((src->size < dst->size) ? src->size : dst->size);
 163         delta_size = max_size - base_size;
 164
 165         /* We would not consider edits that change the file size so
 166          * drastically.  delta_size must be smaller than
 167          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
 168          *
 169          * Note that base_size == 0 case is handled here already
 170          * and the final score computation below would not have a
 171          * divide-by-zero issue.
 172          */
 173         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 174                 return 0;
 175
 176         if (!src->cnt_data && diff_populate_filespec(src, 0))
 177                 return 0;
 178         if (!dst->cnt_data && diff_populate_filespec(dst, 0))
 179                 return 0;
 180
 181         delta_limit = (unsigned long)
 182                 (base_size * (MAX_SCORE-minimum_score) / MAX_SCORE);
 183         if (diffcore_count_changes(src, dst,
 184                                    &src->cnt_data, &dst->cnt_data,
 185                                    delta_limit,
 186                                    &src_copied, &literal_added))
 187                 return 0;
 188
 189         /* How similar are they?
 190          * what percentage of material in dst are from source?
 191          */
 192         if (!dst->size)
 193                 score = 0; /* should not happen */
 194         else
 195                 score = (int)(src_copied * MAX_SCORE / max_size);
 196         return score;
 197 }
 198
 199 static void record_rename_pair(int dst_index, int src_index, int score)
 200 {
 201         struct diff_filespec *src, *dst;
 202         struct diff_filepair *dp;
 203
 204         if (rename_dst[dst_index].pair)
 205                 die("internal error: dst already matched.");
 206
 207         src = rename_src[src_index].one;
 208         src->rename_used++;
 209         src->count++;
 210
 211         dst = rename_dst[dst_index].two;
 212         dst->count++;
 213
 214         dp = diff_queue(NULL, src, dst);
 215         dp->renamed_pair = 1;
 216         if (!strcmp(src->path, dst->path))
 217                 dp->score = rename_src[src_index].score;
 218         else
 219                 dp->score = score;
 220         rename_dst[dst_index].pair = dp;
 221 }
 222
 223 /*
 224  * We sort the rename similarity matrix with the score, in descending
 225  * order (the most similar first).
 226  */
 227 static int score_compare(const void *a_, const void *b_)
 228 {
 229         const struct diff_score *a = a_, *b = b_;
 230
 231         /* sink the unused ones to the bottom */
 232         if (a->dst < 0)
 233                 return (0 <= b->dst);
 234         else if (b->dst < 0)
 235                 return -1;
 236
 237         if (a->score == b->score)
 238                 return b->name_score - a->name_score;
 239
 240         return b->score - a->score;
 241 }
 242
 243 struct file_similarity {
 244         int src_dst, index;
 245         struct diff_filespec *filespec;
 246         struct file_similarity *next;
 247 };
 248
 249 static int find_identical_files(struct file_similarity *src,
 250                                 struct file_similarity *dst)
 251 {
 252         int renames = 0;
 253
 254         /*
 255          * Walk over all the destinations ...
 256          */
 257         do {
 258                 struct diff_filespec *target = dst->filespec;
 259                 struct file_similarity *p, *best;
 260                 int i = 100, best_score = -1;
 261
 262                 /*
 263                  * .. to find the best source match
 264                  */
 265                 best = NULL;
 266                 for (p = src; p; p = p->next) {
 267                         int score;
 268                         struct diff_filespec *source = p->filespec;
 269
 270                         /* False hash collision? */
 271                         if (hashcmp(source->sha1, target->sha1))
 272                                 continue;
 273                         /* Non-regular files? If so, the modes must match! */
 274                         if (!S_ISREG(source->mode) || !S_ISREG(target->mode)) {
 275                                 if (source->mode != target->mode)
 276                                         continue;
 277                         }
 278                         /* Give higher scores to sources that haven't been used already */
 279                         score = !source->rename_used;
 280                         score += basename_same(source, target);
 281                         if (score > best_score) {
 282                                 best = p;
 283                                 best_score = score;
 284                                 if (score == 2)
 285                                         break;
 286                         }
 287
 288                         /* Too many identical alternatives? Pick one */
 289                         if (!--i)
 290                                 break;
 291                 }
 292                 if (best) {
 293                         record_rename_pair(dst->index, best->index, MAX_SCORE);
 294                         renames++;
 295                 }
 296         } while ((dst = dst->next) != NULL);
 297         return renames;
 298 }
 299
 300 static void free_similarity_list(struct file_similarity *p)
 301 {
 302         while (p) {
 303                 struct file_similarity *entry = p;
 304                 p = p->next;
 305                 free(entry);
 306         }
 307 }
 308
 309 static int find_same_files(void *ptr)
 310 {
 311         int ret;
 312         struct file_similarity *p = ptr;
 313         struct file_similarity *src = NULL, *dst = NULL;
 314
 315         /* Split the hash list up into sources and destinations */
 316         do {
 317                 struct file_similarity *entry = p;
 318                 p = p->next;
 319                 if (entry->src_dst < 0) {
 320                         entry->next = src;
 321                         src = entry;
 322                 } else {
 323                         entry->next = dst;
 324                         dst = entry;
 325                 }
 326         } while (p);
 327
 328         /*
 329          * If we have both sources *and* destinations, see if
 330          * we can match them up
 331          */
 332         ret = (src && dst) ? find_identical_files(src, dst) : 0;
 333
 334         /* Free the hashes and return the number of renames found */
 335         free_similarity_list(src);
 336         free_similarity_list(dst);
 337         return ret;
 338 }
 339
 340 static unsigned int hash_filespec(struct diff_filespec *filespec)
 341 {
 342         unsigned int hash;
 343         if (!filespec->sha1_valid) {
 344                 if (diff_populate_filespec(filespec, 0))
 345                         return 0;
 346                 hash_sha1_file(filespec->data, filespec->size, "blob", filespec->sha1);
 347         }
 348         memcpy(&hash, filespec->sha1, sizeof(hash));
 349         return hash;
 350 }
 351
 352 static void insert_file_table(struct hash_table *table, int src_dst, int index, struct diff_filespec *filespec)
 353 {
 354         void **pos;
 355         unsigned int hash;
 356         struct file_similarity *entry = xmalloc(sizeof(*entry));
 357
 358         entry->src_dst = src_dst;
 359         entry->index = index;
 360         entry->filespec = filespec;
 361         entry->next = NULL;
 362
 363         hash = hash_filespec(filespec);
 364         pos = insert_hash(hash, entry, table);
 365
 366         /* We already had an entry there? */
 367         if (pos) {
 368                 entry->next = *pos;
 369                 *pos = entry;
 370         }
 371 }
 372
 373 /*
 374  * Find exact renames first.
 375  *
 376  * The first round matches up the up-to-date entries,
 377  * and then during the second round we try to match
 378  * cache-dirty entries as well.
 379  */
 380 static int find_exact_renames(void)
 381 {
 382         int i;
 383         struct hash_table file_table;
 384
 385         init_hash(&file_table);
 386         for (i = 0; i < rename_src_nr; i++)
 387                 insert_file_table(&file_table, -1, i, rename_src[i].one);
 388
 389         for (i = 0; i < rename_dst_nr; i++)
 390                 insert_file_table(&file_table, 1, i, rename_dst[i].two);
 391
 392         /* Find the renames */
 393         i = for_each_hash(&file_table, find_same_files);
 394
 395         /* .. and free the hash data structure */
 396         free_hash(&file_table);
 397
 398         return i;
 399 }
 400
 401 #define NUM_CANDIDATE_PER_DST 4
 402 static void record_if_better(struct diff_score m[], struct diff_score *o)
 403 {
 404         int i, worst;
 405
 406         /* find the worst one */
 407         worst = 0;
 408         for (i = 1; i < NUM_CANDIDATE_PER_DST; i++)
 409                 if (score_compare(&m[i], &m[worst]) > 0)
 410                         worst = i;
 411
 412         /* is it better than the worst one? */
 413         if (score_compare(&m[worst], o) > 0)
 414                 m[worst] = *o;
 415 }
 416
 417 void diffcore_rename(struct diff_options *options)
 418 {
 419         int detect_rename = options->detect_rename;
 420         int minimum_score = options->rename_score;
 421         int rename_limit = options->rename_limit;
 422         struct diff_queue_struct *q = &diff_queued_diff;
 423         struct diff_queue_struct outq;
 424         struct diff_score *mx;
 425         int i, j, rename_count;
 426         int num_create, num_src, dst_cnt;
 427
 428         if (!minimum_score)
 429                 minimum_score = DEFAULT_RENAME_SCORE;
 430
 431         for (i = 0; i < q->nr; i++) {
 432                 struct diff_filepair *p = q->queue[i];
 433                 if (!DIFF_FILE_VALID(p->one)) {
 434                         if (!DIFF_FILE_VALID(p->two))
 435                                 continue; /* unmerged */
 436                         else if (options->single_follow &&
 437                                  strcmp(options->single_follow, p->two->path))
 438                                 continue; /* not interested */
 439                         else
 440                                 locate_rename_dst(p->two, 1);
 441                 }
 442                 else if (!DIFF_FILE_VALID(p->two)) {
 443                         /*
 444                          * If the source is a broken "delete", and
 445                          * they did not really want to get broken,
 446                          * that means the source actually stays.
 447                          * So we increment the "rename_used" score
 448                          * by one, to indicate ourselves as a user
 449                          */
 450                         if (p->broken_pair && !p->score)
 451                                 p->one->rename_used++;
 452                         register_rename_src(p->one, p->score);
 453                 }
 454                 else if (detect_rename == DIFF_DETECT_COPY) {
 455                         /*
 456                          * Increment the "rename_used" score by
 457                          * one, to indicate ourselves as a user.
 458                          */
 459                         p->one->rename_used++;
 460                         register_rename_src(p->one, p->score);
 461                 }
 462         }
 463         if (rename_dst_nr == 0 || rename_src_nr == 0)
 464                 goto cleanup; /* nothing to do */
 465
 466         /*
 467          * We really want to cull the candidates list early
 468          * with cheap tests in order to avoid doing deltas.
 469          */
 470         rename_count = find_exact_renames();
 471
 472         /* Did we only want exact renames? */
 473         if (minimum_score == MAX_SCORE)
 474                 goto cleanup;
 475
 476         /*
 477          * Calculate how many renames are left (but all the source
 478          * files still remain as options for rename/copies!)
 479          */
 480         num_create = (rename_dst_nr - rename_count);
 481         num_src = rename_src_nr;
 482
 483         /* All done? */
 484         if (!num_create)
 485                 goto cleanup;
 486
 487         /*
 488          * This basically does a test for the rename matrix not
 489          * growing larger than a "rename_limit" square matrix, ie:
 490          *
 491          *    num_create * num_src > rename_limit * rename_limit
 492          *
 493          * but handles the potential overflow case specially (and we
 494          * assume at least 32-bit integers)
 495          */
 496         if (rename_limit <= 0 || rename_limit > 32767)
 497                 rename_limit = 32767;
 498         if ((num_create > rename_limit && num_src > rename_limit) ||
 499             (num_create * num_src > rename_limit * rename_limit)) {
 500                 if (options->warn_on_too_large_rename)
 501                         warning("too many files (created: %d deleted: %d), skipping inexact rename detection", num_create, num_src);
 502                 goto cleanup;
 503         }
 504
 505         mx = xcalloc(num_create * NUM_CANDIDATE_PER_DST, sizeof(*mx));
 506         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 507                 struct diff_filespec *two = rename_dst[i].two;
 508                 struct diff_score *m;
 509
 510                 if (rename_dst[i].pair)
 511                         continue; /* dealt with exact match already. */
 512
 513                 m = &mx[dst_cnt * NUM_CANDIDATE_PER_DST];
 514                 for (j = 0; j < NUM_CANDIDATE_PER_DST; j++)
 515                         m[j].dst = -1;
 516
 517                 for (j = 0; j < rename_src_nr; j++) {
 518                         struct diff_filespec *one = rename_src[j].one;
 519                         struct diff_score this_src;
 520                         this_src.score = estimate_similarity(one, two,
 521                                                              minimum_score);
 522                         this_src.name_score = basename_same(one, two);
 523                         this_src.dst = i;
 524                         this_src.src = j;
 525                         record_if_better(m, &this_src);
 526                         /*
 527                          * Once we run estimate_similarity,
 528                          * We do not need the text anymore.
 529                          */
 530                         diff_free_filespec_blob(one);
 531                         diff_free_filespec_blob(two);
 532                 }
 533                 dst_cnt++;
 534         }
 535
 536         /* cost matrix sorted by most to least similar pair */
 537         qsort(mx, dst_cnt * NUM_CANDIDATE_PER_DST, sizeof(*mx), score_compare);
 538
 539         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
 540                 struct diff_rename_dst *dst;
 541
 542                 if ((mx[i].dst < 0) ||
 543                     (mx[i].score < minimum_score))
 544                         break; /* there is no more usable pair. */
 545                 dst = &rename_dst[mx[i].dst];
 546                 if (dst->pair)
 547                         continue; /* already done, either exact or fuzzy. */
 548                 if (rename_src[mx[i].src].one->rename_used)
 549                         continue;
 550                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
 551                 rename_count++;
 552         }
 553
 554         for (i = 0; i < dst_cnt * NUM_CANDIDATE_PER_DST; i++) {
 555                 struct diff_rename_dst *dst;
 556
 557                 if ((mx[i].dst < 0) ||
 558                     (mx[i].score < minimum_score))
 559                         break; /* there is no more usable pair. */
 560                 dst = &rename_dst[mx[i].dst];
 561                 if (dst->pair)
 562                         continue; /* already done, either exact or fuzzy. */
 563                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
 564                 rename_count++;
 565         }
 566         free(mx);
 567
 568  cleanup:
 569         /* At this point, we have found some renames and copies and they
 570          * are recorded in rename_dst.  The original list is still in *q.
 571          */
 572         outq.queue = NULL;
 573         outq.nr = outq.alloc = 0;
 574         for (i = 0; i < q->nr; i++) {
 575                 struct diff_filepair *p = q->queue[i];
 576                 struct diff_filepair *pair_to_free = NULL;
 577
 578                 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
 579                         /*
 580                          * Creation
 581                          *
 582                          * We would output this create record if it has
 583                          * not been turned into a rename/copy already.
 584                          */
 585                         struct diff_rename_dst *dst =
 586                                 locate_rename_dst(p->two, 0);
 587                         if (dst && dst->pair) {
 588                                 diff_q(&outq, dst->pair);
 589                                 pair_to_free = p;
 590                         }
 591                         else
 592                                 /* no matching rename/copy source, so
 593                                  * record this as a creation.
 594                                  */
 595                                 diff_q(&outq, p);
 596                 }
 597                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
 598                         /*
 599                          * Deletion
 600                          *
 601                          * We would output this delete record if:
 602                          *
 603                          * (1) this is a broken delete and the counterpart
 604                          *     broken create remains in the output; or
 605                          * (2) this is not a broken delete, and rename_dst
 606                          *     does not have a rename/copy to move p->one->path
 607                          *     out of existence.
 608                          *
 609                          * Otherwise, the counterpart broken create
 610                          * has been turned into a rename-edit; or
 611                          * delete did not have a matching create to
 612                          * begin with.
 613                          */
 614                         if (DIFF_PAIR_BROKEN(p)) {
 615                                 /* broken delete */
 616                                 struct diff_rename_dst *dst =
 617                                         locate_rename_dst(p->one, 0);
 618                                 if (dst && dst->pair)
 619                                         /* counterpart is now rename/copy */
 620                                         pair_to_free = p;
 621                         }
 622                         else {
 623                                 if (p->one->rename_used)
 624                                         /* this path remains */
 625                                         pair_to_free = p;
 626                         }
 627
 628                         if (pair_to_free)
 629                                 ;
 630                         else
 631                                 diff_q(&outq, p);
 632                 }
 633                 else if (!diff_unmodified_pair(p))
 634                         /* all the usual ones need to be kept */
 635                         diff_q(&outq, p);
 636                 else
 637                         /* no need to keep unmodified pairs */
 638                         pair_to_free = p;
 639
 640                 if (pair_to_free)
 641                         diff_free_filepair(pair_to_free);
 642         }
 643         diff_debug_queue("done copying original", &outq);
 644
 645         free(q->queue);
 646         *q = outq;
 647         diff_debug_queue("done collapsing", q);
 648
 649         for (i = 0; i < rename_dst_nr; i++)
 650                 free_filespec(rename_dst[i].two);
 651
 652         free(rename_dst);
 653         rename_dst = NULL;
 654         rename_dst_nr = rename_dst_alloc = 0;
 655         free(rename_src);
 656         rename_src = NULL;
 657         rename_src_nr = rename_src_alloc = 0;
 658         return;
 659 }