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