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 short score; /* to remember the break score */
  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                                                    unsigned short score)
  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].score = score;
  95         rename_src[first].src_path_left = src_path_left;
  96         return &(rename_src[first]);
  97 }
  98
  99 static int is_exact_match(struct diff_filespec *src, struct diff_filespec *dst)
 100 {
 101         if (src->sha1_valid && dst->sha1_valid &&
 102             !memcmp(src->sha1, dst->sha1, 20))
 103                 return 1;
 104         if (diff_populate_filespec(src, 1) || diff_populate_filespec(dst, 1))
 105                 return 0;
 106         if (src->size != dst->size)
 107                 return 0;
 108         if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
 109                 return 0;
 110         if (src->size == dst->size &&
 111             !memcmp(src->data, dst->data, src->size))
 112                 return 1;
 113         return 0;
 114 }
 115
 116 struct diff_score {
 117         int src; /* index in rename_src */
 118         int dst; /* index in rename_dst */
 119         int score;
 120 };
 121
 122 static int estimate_similarity(struct diff_filespec *src,
 123                                struct diff_filespec *dst,
 124                                int minimum_score)
 125 {
 126         /* src points at a file that existed in the original tree (or
 127          * optionally a file in the destination tree) and dst points
 128          * at a newly created file.  They may be quite similar, in which
 129          * case we want to say src is renamed to dst or src is copied into
 130          * dst, and then some edit has been applied to dst.
 131          *
 132          * Compare them and return how similar they are, representing
 133          * the score as an integer between 0 and MAX_SCORE.
 134          *
 135          * When there is an exact match, it is considered a better
 136          * match than anything else; the destination does not even
 137          * call into this function in that case.
 138          */
 139         unsigned long max_size, 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         max_size = ((src->size > dst->size) ? src->size : dst->size);
 151         base_size = ((src->size < dst->size) ? src->size : dst->size);
 152         delta_size = max_size - base_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
 169         delta_limit = base_size * (MAX_SCORE-minimum_score) / MAX_SCORE;
 170         if (diffcore_count_changes(src->data, src->size,
 171                                    dst->data, dst->size,
 172                                    &src->cnt_data, &dst->cnt_data,
 173                                    delta_limit,
 174                                    &src_copied, &literal_added))
 175                 return 0;
 176
 177         /* How similar are they?
 178          * what percentage of material in dst are from source?
 179          */
 180         if (!dst->size)
 181                 score = 0; /* should not happen */
 182         else
 183                 score = src_copied * MAX_SCORE / max_size;
 184         return score;
 185 }
 186
 187 static void record_rename_pair(int dst_index, int src_index, int score)
 188 {
 189         struct diff_filespec *one, *two, *src, *dst;
 190         struct diff_filepair *dp;
 191
 192         if (rename_dst[dst_index].pair)
 193                 die("internal error: dst already matched.");
 194
 195         src = rename_src[src_index].one;
 196         one = alloc_filespec(src->path);
 197         fill_filespec(one, src->sha1, src->mode);
 198
 199         dst = rename_dst[dst_index].two;
 200         two = alloc_filespec(dst->path);
 201         fill_filespec(two, dst->sha1, dst->mode);
 202
 203         dp = diff_queue(NULL, one, two);
 204         if (!strcmp(src->path, dst->path))
 205                 dp->score = rename_src[src_index].score;
 206         else
 207                 dp->score = score;
 208         dp->source_stays = rename_src[src_index].src_path_left;
 209         rename_dst[dst_index].pair = dp;
 210 }
 211
 212 /*
 213  * We sort the rename similarity matrix with the score, in descending
 214  * order (the most similar first).
 215  */
 216 static int score_compare(const void *a_, const void *b_)
 217 {
 218         const struct diff_score *a = a_, *b = b_;
 219         return b->score - a->score;
 220 }
 221
 222 static int compute_stays(struct diff_queue_struct *q,
 223                          struct diff_filespec *one)
 224 {
 225         int i;
 226         for (i = 0; i < q->nr; i++) {
 227                 struct diff_filepair *p = q->queue[i];
 228                 if (strcmp(one->path, p->two->path))
 229                         continue;
 230                 if (DIFF_PAIR_RENAME(p)) {
 231                         return 0; /* something else is renamed into this */
 232                 }
 233         }
 234         return 1;
 235 }
 236
 237 void diffcore_rename(struct diff_options *options)
 238 {
 239         int detect_rename = options->detect_rename;
 240         int minimum_score = options->rename_score;
 241         int rename_limit = options->rename_limit;
 242         struct diff_queue_struct *q = &diff_queued_diff;
 243         struct diff_queue_struct outq;
 244         struct diff_score *mx;
 245         int i, j, rename_count;
 246         int num_create, num_src, dst_cnt;
 247
 248         if (!minimum_score)
 249                 minimum_score = DEFAULT_RENAME_SCORE;
 250         rename_count = 0;
 251
 252         for (i = 0; i < q->nr; i++) {
 253                 struct diff_filepair *p = q->queue[i];
 254                 if (!DIFF_FILE_VALID(p->one))
 255                         if (!DIFF_FILE_VALID(p->two))
 256                                 continue; /* unmerged */
 257                         else
 258                                 locate_rename_dst(p->two, 1);
 259                 else if (!DIFF_FILE_VALID(p->two)) {
 260                         /* If the source is a broken "delete", and
 261                          * they did not really want to get broken,
 262                          * that means the source actually stays.
 263                          */
 264                         int stays = (p->broken_pair && !p->score);
 265                         register_rename_src(p->one, stays, p->score);
 266                 }
 267                 else if (detect_rename == DIFF_DETECT_COPY)
 268                         register_rename_src(p->one, 1, p->score);
 269         }
 270         if (rename_dst_nr == 0 || rename_src_nr == 0 ||
 271             (0 < rename_limit && rename_limit < rename_dst_nr))
 272                 goto cleanup; /* nothing to do */
 273
 274         /* We really want to cull the candidates list early
 275          * with cheap tests in order to avoid doing deltas.
 276          */
 277         for (i = 0; i < rename_dst_nr; i++) {
 278                 struct diff_filespec *two = rename_dst[i].two;
 279                 for (j = 0; j < rename_src_nr; j++) {
 280                         struct diff_filespec *one = rename_src[j].one;
 281                         if (!is_exact_match(one, two))
 282                                 continue;
 283                         record_rename_pair(i, j, MAX_SCORE);
 284                         rename_count++;
 285                         break; /* we are done with this entry */
 286                 }
 287         }
 288
 289         /* Have we run out the created file pool?  If so we can avoid
 290          * doing the delta matrix altogether.
 291          */
 292         if (rename_count == rename_dst_nr)
 293                 goto cleanup;
 294
 295         if (minimum_score == MAX_SCORE)
 296                 goto cleanup;
 297
 298         num_create = (rename_dst_nr - rename_count);
 299         num_src = rename_src_nr;
 300         mx = xmalloc(sizeof(*mx) * num_create * num_src);
 301         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 302                 int base = dst_cnt * num_src;
 303                 struct diff_filespec *two = rename_dst[i].two;
 304                 if (rename_dst[i].pair)
 305                         continue; /* dealt with exact match already. */
 306                 for (j = 0; j < rename_src_nr; j++) {
 307                         struct diff_filespec *one = rename_src[j].one;
 308                         struct diff_score *m = &mx[base+j];
 309                         m->src = j;
 310                         m->dst = i;
 311                         m->score = estimate_similarity(one, two,
 312                                                        minimum_score);
 313                 }
 314                 /* We do not need the text anymore */
 315                 diff_free_filespec_data(two);
 316                 dst_cnt++;
 317         }
 318         /* cost matrix sorted by most to least similar pair */
 319         qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
 320         for (i = 0; i < num_create * num_src; i++) {
 321                 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
 322                 if (dst->pair)
 323                         continue; /* already done, either exact or fuzzy. */
 324                 if (mx[i].score < minimum_score)
 325                         break; /* there is no more usable pair. */
 326                 record_rename_pair(mx[i].dst, mx[i].src, mx[i].score);
 327                 rename_count++;
 328         }
 329         free(mx);
 330
 331  cleanup:
 332         /* At this point, we have found some renames and copies and they
 333          * are recorded in rename_dst.  The original list is still in *q.
 334          */
 335         outq.queue = NULL;
 336         outq.nr = outq.alloc = 0;
 337         for (i = 0; i < q->nr; i++) {
 338                 struct diff_filepair *p = q->queue[i];
 339                 struct diff_filepair *pair_to_free = NULL;
 340
 341                 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
 342                         /*
 343                          * Creation
 344                          *
 345                          * We would output this create record if it has
 346                          * not been turned into a rename/copy already.
 347                          */
 348                         struct diff_rename_dst *dst =
 349                                 locate_rename_dst(p->two, 0);
 350                         if (dst && dst->pair) {
 351                                 diff_q(&outq, dst->pair);
 352                                 pair_to_free = p;
 353                         }
 354                         else
 355                                 /* no matching rename/copy source, so
 356                                  * record this as a creation.
 357                                  */
 358                                 diff_q(&outq, p);
 359                 }
 360                 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
 361                         /*
 362                          * Deletion
 363                          *
 364                          * We would output this delete record if:
 365                          *
 366                          * (1) this is a broken delete and the counterpart
 367                          *     broken create remains in the output; or
 368                          * (2) this is not a broken delete, and rename_dst
 369                          *     does not have a rename/copy to move p->one->path
 370                          *     out of existence.
 371                          *
 372                          * Otherwise, the counterpart broken create
 373                          * has been turned into a rename-edit; or
 374                          * delete did not have a matching create to
 375                          * begin with.
 376                          */
 377                         if (DIFF_PAIR_BROKEN(p)) {
 378                                 /* broken delete */
 379                                 struct diff_rename_dst *dst =
 380                                         locate_rename_dst(p->one, 0);
 381                                 if (dst && dst->pair)
 382                                         /* counterpart is now rename/copy */
 383                                         pair_to_free = p;
 384                         }
 385                         else {
 386                                 for (j = 0; j < rename_dst_nr; j++) {
 387                                         if (!rename_dst[j].pair)
 388                                                 continue;
 389                                         if (strcmp(rename_dst[j].pair->
 390                                                    one->path,
 391                                                    p->one->path))
 392                                                 continue;
 393                                         break;
 394                                 }
 395                                 if (j < rename_dst_nr)
 396                                         /* this path remains */
 397                                         pair_to_free = p;
 398                         }
 399
 400                         if (pair_to_free)
 401                                 ;
 402                         else
 403                                 diff_q(&outq, p);
 404                 }
 405                 else if (!diff_unmodified_pair(p))
 406                         /* all the usual ones need to be kept */
 407                         diff_q(&outq, p);
 408                 else
 409                         /* no need to keep unmodified pairs */
 410                         pair_to_free = p;
 411
 412                 if (pair_to_free)
 413                         diff_free_filepair(pair_to_free);
 414         }
 415         diff_debug_queue("done copying original", &outq);
 416
 417         free(q->queue);
 418         *q = outq;
 419         diff_debug_queue("done collapsing", q);
 420
 421         /* We need to see which rename source really stays here;
 422          * earlier we only checked if the path is left in the result,
 423          * but even if a path remains in the result, if that is coming
 424          * from copying something else on top of it, then the original
 425          * source is lost and does not stay.
 426          */
 427         for (i = 0; i < q->nr; i++) {
 428                 struct diff_filepair *p = q->queue[i];
 429                 if (DIFF_PAIR_RENAME(p) && p->source_stays) {
 430                         /* If one appears as the target of a rename-copy,
 431                          * then mark p->source_stays = 0; otherwise
 432                          * leave it as is.
 433                          */
 434                         p->source_stays = compute_stays(q, p->one);
 435                 }
 436         }
 437
 438         for (i = 0; i < rename_dst_nr; i++) {
 439                 diff_free_filespec_data(rename_dst[i].two);
 440                 free(rename_dst[i].two);
 441         }
 442
 443         free(rename_dst);
 444         rename_dst = NULL;
 445         rename_dst_nr = rename_dst_alloc = 0;
 446         free(rename_src);
 447         rename_src = NULL;
 448         rename_src_nr = rename_src_alloc = 0;
 449         return;
 450 }