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 "delta.h"
   8 #include "count-delta.h"
   9
  10 /* Table of rename/copy destinations */
  11
  12 static struct diff_rename_dst {
  13         struct diff_filespec *two;
  14         struct diff_filepair *pair;
  15 } *rename_dst;
  16 static int rename_dst_nr, rename_dst_alloc;
  17
  18 static struct diff_rename_dst *locate_rename_dst(struct diff_filespec *two,
  19                                                  int insert_ok)
  20 {
  21         int first, last;
  22
  23         first = 0;
  24         last = rename_dst_nr;
  25         while (last > first) {
  26                 int next = (last + first) >> 1;
  27                 struct diff_rename_dst *dst = &(rename_dst[next]);
  28                 int cmp = strcmp(two->path, dst->two->path);
  29                 if (!cmp)
  30                         return dst;
  31                 if (cmp < 0) {
  32                         last = next;
  33                         continue;
  34                 }
  35                 first = next+1;
  36         }
  37         /* not found */
  38         if (!insert_ok)
  39                 return NULL;
  40         /* insert to make it at "first" */
  41         if (rename_dst_alloc <= rename_dst_nr) {
  42                 rename_dst_alloc = alloc_nr(rename_dst_alloc);
  43                 rename_dst = xrealloc(rename_dst,
  44                                       rename_dst_alloc * sizeof(*rename_dst));
  45         }
  46         rename_dst_nr++;
  47         if (first < rename_dst_nr)
  48                 memmove(rename_dst + first + 1, rename_dst + first,
  49                         (rename_dst_nr - first - 1) * sizeof(*rename_dst));
  50         rename_dst[first].two = alloc_filespec(two->path);
  51         fill_filespec(rename_dst[first].two, two->sha1, two->mode);
  52         rename_dst[first].pair = NULL;
  53         return &(rename_dst[first]);
  54 }
  55
  56 /* Table of rename/copy src files */
  57 static struct diff_rename_src {
  58         struct diff_filespec *one;
  59         unsigned src_path_left : 1;
  60 } *rename_src;
  61 static int rename_src_nr, rename_src_alloc;
  62
  63 static struct diff_rename_src *register_rename_src(struct diff_filespec *one,
  64                                                    int src_path_left)
  65 {
  66         int first, last;
  67
  68         first = 0;
  69         last = rename_src_nr;
  70         while (last > first) {
  71                 int next = (last + first) >> 1;
  72                 struct diff_rename_src *src = &(rename_src[next]);
  73                 int cmp = strcmp(one->path, src->one->path);
  74                 if (!cmp)
  75                         return src;
  76                 if (cmp < 0) {
  77                         last = next;
  78                         continue;
  79                 }
  80                 first = next+1;
  81         }
  82
  83         /* insert to make it at "first" */
  84         if (rename_src_alloc <= rename_src_nr) {
  85                 rename_src_alloc = alloc_nr(rename_src_alloc);
  86                 rename_src = xrealloc(rename_src,
  87                                       rename_src_alloc * sizeof(*rename_src));
  88         }
  89         rename_src_nr++;
  90         if (first < rename_src_nr)
  91                 memmove(rename_src + first + 1, rename_src + first,
  92                         (rename_src_nr - first - 1) * sizeof(*rename_src));
  93         rename_src[first].one = one;
  94         rename_src[first].src_path_left = src_path_left;
  95         return &(rename_src[first]);
  96 }
  97
  98 static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
  99 {
 100         if (src->sha1_valid && dst->sha1_valid &&
 101             !memcmp(src->sha1, dst->sha1, 20))
 102                 return 1;
 103         if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1))
 104                 return 0;
 105         if (src->size != dst->size)
 106                 return 0;
 107         if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
 108                 return 0;
 109         if (src->size == dst->size &&
 110             !memcmp(src->data, dst->data, src->size))
 111                 return 1;
 112         return 0;
 113 }
 114
 115 struct diff_score {
 116         int src; /* index in rename_src */
 117         int dst; /* index in rename_dst */
 118         int score;
 119 };
 120
 121 static int estimate_similarity(struct diff_filespec *src,
 122                                struct diff_filespec *dst,
 123                                int minimum_score)
 124 {
 125         /* src points at a file that existed in the original tree (or
 126          * optionally a file in the destination tree) and dst points
 127          * at a newly created file.  They may be quite similar, in which
 128          * case we want to say src is renamed to dst or src is copied into
 129          * dst, and then some edit has been applied to dst.
 130          *
 131          * Compare them and return how similar they are, representing
 132          * the score as an integer between 0 and MAX_SCORE.
 133          *
 134          * When there is an exact match, it is considered a better
 135          * match than anything else; the destination does not even
 136          * call into this function in that case.
 137          */
 138         void *delta;
 139         unsigned long delta_size, base_size, src_copied, literal_added;
 140         unsigned long delta_limit;
 141         int score;
 142
 143         /* We deal only with regular files.  Symlink renames are handled
 144          * only when they are exact matches --- in other words, no edits
 145          * after renaming.
 146          */
 147         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
 148                 return 0;
 149
 150         delta_size = ((src->size < dst->size) ?
 151                       (dst->size - src->size) : (src->size - dst->size));
 152         base_size = ((src->size < dst->size) ? src->size : dst->size);
 153
 154         /* We would not consider edits that change the file size so
 155          * drastically.  delta_size must be smaller than
 156          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
 157          *
 158          * Note that base_size == 0 case is handled here already
 159          * and the final score computation below would not have a
 160          * divide-by-zero issue.
 161          */
 162         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 163                 return 0;
 164
 165         if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
 166                 return 0; /* error but caught downstream */
 167
 168         delta_limit = base_size * (MAX_SCORE-minimum_score) / MAX_SCORE;
 169         delta = diff_delta(src->data, src->size,
 170                            dst->data, dst->size,
 171                            &delta_size, delta_limit);
 172         if (!delta)
 173                 /* If delta_limit is exceeded, we have too much differences */
 174                 return 0;
 175
 176         /* A delta that has a lot of literal additions would have
 177          * big delta_size no matter what else it does.
 178          */
 179         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE) {
 180                 free(delta);
 181                 return 0;
 182         }
 183
 184         /* Estimate the edit size by interpreting delta. */
 185         if (count_delta(delta, delta_size, &src_copied, &literal_added)) {
 186                 free(delta);
 187                 return 0;
 188         }
 189         free(delta);
 190
 191         /* Extent of damage */
 192         if (src->size + literal_added < src_copied)
 193                 delta_size = 0;
 194         else
 195                 delta_size = (src->size - src_copied) + literal_added;
 196
 197         /*
 198          * Now we will give some score to it.  100% edit gets 0 points
 199          * and 0% edit gets MAX_SCORE points.
 200          */
 201         score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
 202         if (score < 0) return 0;
 203         if (MAX_SCORE < score) return MAX_SCORE;
 204         return score;
 205 }
 206
 207 static void record_rename_pair(int dst_index, int src_index, int score)
 208 {
 209         struct diff_filespec *one, *two, *src, *dst;
 210         struct diff_filepair *dp;
 211
 212         if (rename_dst[dst_index].pair)
 213                 die("internal error: dst already matched.");
 214
 215         src = rename_src[src_index].one;
 216         one = alloc_filespec(src->path);
 217         fill_filespec(one, src->sha1, src->mode);
 218
 219         dst = rename_dst[dst_index].two;
 220         two = alloc_filespec(dst->path);
 221         fill_filespec(two, dst->sha1, dst->mode);
 222
 223         dp = diff_queue(NULL, one, two);
 224         dp->score = score;
 225         dp->source_stays = rename_src[src_index].src_path_left;
 226         rename_dst[dst_index].pair = dp;
 227 }
 228
 229 /*
 230  * We sort the rename similarity matrix with the score, in descending
 231  * order (the most similar first).
 232  */
 233 static int score_compare(const void *a_, const void *b_)
 234 {
 235         const struct diff_score *a = a_, *b = b_;
 236         return b->score - a->score;
 237 }
 238
 239 static int compute_stays(struct diff_queue_struct *q,
 240                          struct diff_filespec *one)
 241 {
 242         int i;
 243         for (i = 0; i < q->nr; i++) {
 244                 struct diff_filepair *p = q->queue[i];
 245                 if (strcmp(one->path, p->two->path))
 246                         continue;
 247                 if (DIFF_PAIR_RENAME(p)) {
 248                         return 0; /* something else is renamed into this */
 249                 }
 250         }
 251         return 1;
 252 }
 253
 254 void diffcore_rename(struct diff_options *options)
 255 {
 256         int detect_rename = options->detect_rename;
 257         int minimum_score = options->rename_score;
 258         int rename_limit = options->rename_limit;
 259         struct diff_queue_struct *q = &diff_queued_diff;
 260         struct diff_queue_struct outq;
 261         struct diff_score *mx;
 262         int i, j, rename_count;
 263         int num_create, num_src, dst_cnt;
 264
 265         if (!minimum_score)
 266                 minimum_score = DEFAULT_RENAME_SCORE;
 267         rename_count = 0;
 268
 269         for (i = 0; i < q->nr; i++) {
 270                 struct diff_filepair *p = q->queue[i];
 271                 if (!DIFF_FILE_VALID(p->one))
 272                         if (!DIFF_FILE_VALID(p->two))
 273                                 continue; /* unmerged */
 274                         else
 275                                 locate_rename_dst(p->two, 1);
 276                 else if (!DIFF_FILE_VALID(p->two)) {
 277                         /* If the source is a broken "delete", and
 278                          * they did not really want to get broken,
 279                          * that means the source actually stays.
 280                          */
 281                         int stays = (p->broken_pair && !p->score);
 282                         register_rename_src(p->one, stays);
 283                 }
 284                 else if (detect_rename == DIFF_DETECT_COPY)
 285                         register_rename_src(p->one, 1);
 286         }
 287         if (rename_dst_nr == 0 || rename_src_nr == 0 ||
 288             (0 < rename_limit && rename_limit < rename_dst_nr))
 289                 goto cleanup; /* nothing to do */
 290
 291         /* We really want to cull the candidates list early
 292          * with cheap tests in order to avoid doing deltas.
 293          */
 294         for (i = 0; i < rename_dst_nr; i++) {
 295                 struct diff_filespec *two = rename_dst[i].two;
 296                 for (j = 0; j < rename_src_nr; j++) {
 297                         struct diff_filespec *one = rename_src[j].one;
 298                         if (!is_exact_match(one, two))
 299                                 continue;
 300                         record_rename_pair(i, j, MAX_SCORE);
 301                         rename_count++;
 302                         break; /* we are done with this entry */
 303                 }
 304         }
 305
 306         /* Have we run out the created file pool?  If so we can avoid
 307          * doing the delta matrix altogether.
 308          */
 309         if (rename_count == rename_dst_nr)
 310                 goto cleanup;
 311
 312         if (minimum_score == MAX_SCORE)
 313                 goto cleanup;
 314
 315         num_create = (rename_dst_nr - rename_count);
 316         num_src = rename_src_nr;
 317         mx = xmalloc(sizeof(*mx) * num_create * num_src);
 318         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 319                 int base = dst_cnt * num_src;
 320                 struct diff_filespec *two = rename_dst[i].two;
 321                 if (rename_dst[i].pair)
 322                         continue; /* dealt with exact match already. */
 323                 for (j = 0; j < rename_src_nr; j++) {
 324                         struct diff_filespec *one = rename_src[j].one;
 325                         struct diff_score *m = &mx[base+j];
 326                         m->src = j;
 327                         m->dst = i;
 328                         m->score = estimate_similarity(one, two,
 329                                                        minimum_score);
 330                 }
 331                 dst_cnt++;
 332         }
 333         /* cost matrix sorted by most to least similar pair */
 334         qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
 335         for (i = 0; i < num_create * num_src; i++) {
 336                 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
 337                 if (dst->pair)
 338                         continue; /* already done, either exact or fuzzy. */
 339                 if (mx[i].score < minimum_score)
 340                         break; /* there is no more usable pair. */
 341                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
 342                 rename_count++;
 343         }
 344         free(mx);
 345
 346  cleanup:
 347         /* At this point, we have found some renames and copies and they
 348          * are recorded in rename_dst.  The original list is still in *q.
 349          */
 350         outq.queue = NULL;
 351         outq.nr = outq.alloc = 0;
 352         for (i = 0; i < q->nr; i++) {
 353                 struct diff_filepair *p = q->queue[i];
 354                 struct diff_filepair *pair_to_free = NULL;
 355
 356                 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
 357                         /*
 358                          * Creation
 359                          *
 360                          * We would output this create record if it has
 361                          * not been turned into a rename/copy already.
 362                          */
 363                         struct diff_rename_dst *dst =
 364                                 locate_rename_dst(p->two, 0);
 365                         if (dst && dst->pair) {
 366                                 diff_q(&outq, dst->pair);
 367                                 pair_to_free = p;
 368                         }
 369                         else
 370                                 /* no matching rename/copy source, so
 371                                  * record this as a creation.
 372                                  */
 373                                 diff_q(&outq, p);
 374                 }
 375                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
 376                         /*
 377                          * Deletion
 378                          *
 379                          * We would output this delete record if:
 380                          *
 381                          * (1) this is a broken delete and the counterpart
 382                          *     broken create remains in the output; or
 383                          * (2) this is not a broken delete, and rename_dst
 384                          *     does not have a rename/copy to move p->one->path
 385                          *     out of existence.
 386                          *
 387                          * Otherwise, the counterpart broken create
 388                          * has been turned into a rename-edit; or
 389                          * delete did not have a matching create to
 390                          * begin with.
 391                          */
 392                         if (DIFF_PAIR_BROKEN(p)) {
 393                                 /* broken delete */
 394                                 struct diff_rename_dst *dst =
 395                                         locate_rename_dst(p->one, 0);
 396                                 if (dst && dst->pair)
 397                                         /* counterpart is now rename/copy */
 398                                         pair_to_free = p;
 399                         }
 400                         else {
 401                                 for (j = 0; j < rename_dst_nr; j++) {
 402                                         if (!rename_dst[j].pair)
 403                                                 continue;
 404                                         if (strcmp(rename_dst[j].pair->
 405                                                    one->path,
 406                                                    p->one->path))
 407                                                 continue;
 408                                         break;
 409                                 }
 410                                 if (j < rename_dst_nr)
 411                                         /* this path remains */
 412                                         pair_to_free = p;
 413                         }
 414
 415                         if (pair_to_free)
 416                                 ;
 417                         else
 418                                 diff_q(&outq, p);
 419                 }
 420                 else if (!diff_unmodified_pair(p))
 421                         /* all the usual ones need to be kept */
 422                         diff_q(&outq, p);
 423                 else
 424                         /* no need to keep unmodified pairs */
 425                         pair_to_free = p;
 426
 427                 if (pair_to_free)
 428                         diff_free_filepair(pair_to_free);
 429         }
 430         diff_debug_queue("done copying original", &outq);
 431
 432         free(q->queue);
 433         *q = outq;
 434         diff_debug_queue("done collapsing", q);
 435
 436         /* We need to see which rename source really stays here;
 437          * earlier we only checked if the path is left in the result,
 438          * but even if a path remains in the result, if that is coming
 439          * from copying something else on top of it, then the original
 440          * source is lost and does not stay.
 441          */
 442         for (i = 0; i < q->nr; i++) {
 443                 struct diff_filepair *p = q->queue[i];
 444                 if (DIFF_PAIR_RENAME(p) && p->source_stays) {
 445                         /* If one appears as the target of a rename-copy,
 446                          * then mark p->source_stays = 0; otherwise
 447                          * leave it as is.
 448                          */
 449                         p->source_stays = compute_stays(q, p->one);
 450                 }
 451         }
 452
 453         for (i = 0; i < rename_dst_nr; i++) {
 454                 diff_free_filespec_data(rename_dst[i].two);
 455                 free(rename_dst[i].two);
 456         }
 457
 458         free(rename_dst);
 459         rename_dst = NULL;
 460         rename_dst_nr = rename_dst_alloc = 0;
 461         free(rename_src);
 462         rename_src = NULL;
 463         rename_src_nr = rename_src_alloc = 0;
 464         return;
 465 }