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