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 static struct diff_rename_src {
  56         struct diff_filespec *one;
  57         unsigned src_used : 1;
  58 } *rename_src;
  59 static int rename_src_nr, rename_src_alloc;
  60
  61 static struct diff_rename_src *locate_rename_src(struct diff_filespec *one,
  62                                                  int insert_ok)
  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         /* not found */
  81         if (!insert_ok)
  82                 return NULL;
  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_used = 0;
  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) || diff_populate_filespec(dst))
 104                 /* this is an error but will be caught downstream */
 105                 return 0;
 106         if (src->size == dst->size &&
 107             !memcmp(src->data, dst->data, src->size))
 108                 return 1;
 109         return 0;
 110 }
 111
 112 struct diff_score {
 113         int src; /* index in rename_src */
 114         int dst; /* index in rename_dst */
 115         int score;
 116         int rank;
 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 10000, except
 131          * where they match exactly it is considered better than anything
 132          * else.
 133          */
 134         void *delta;
 135         unsigned long delta_size, base_size;
 136         int score;
 137
 138         /* We deal only with regular files.  Symlink renames are handled
 139          * only when they are exact matches --- in other words, no edits
 140          * after renaming.
 141          */
 142         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
 143                 return 0;
 144
 145         delta_size = ((src->size < dst->size) ?
 146                       (dst->size - src->size) : (src->size - dst->size));
 147         base_size = ((src->size < dst->size) ? src->size : dst->size);
 148
 149         /* We would not consider edits that change the file size so
 150          * drastically.  delta_size must be smaller than
 151          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
 152          * Note that base_size == 0 case is handled here already
 153          * and the final score computation below would not have a
 154          * divide-by-zero issue.
 155          */
 156         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 157                 return 0;
 158
 159         delta = diff_delta(src->data, src->size,
 160                            dst->data, dst->size,
 161                            &delta_size);
 162
 163         /* A delta that has a lot of literal additions would have
 164          * big delta_size no matter what else it does.
 165          */
 166         if (minimum_score < MAX_SCORE * delta_size / base_size)
 167                 return 0;
 168
 169         /* Estimate the edit size by interpreting delta. */
 170         delta_size = count_delta(delta, delta_size);
 171         free(delta);
 172         if (delta_size == UINT_MAX)
 173                 return 0;
 174
 175         /*
 176          * Now we will give some score to it.  100% edit gets 0 points
 177          * and 0% edit gets MAX_SCORE points.
 178          */
 179         score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
 180         if (score < 0) return 0;
 181         if (MAX_SCORE < score) return MAX_SCORE;
 182         return score;
 183 }
 184
 185 static void record_rename_pair(struct diff_queue_struct *renq,
 186                                int dst_index, int src_index, int score)
 187 {
 188         struct diff_filespec *one, *two, *src, *dst;
 189         struct diff_filepair *dp;
 190
 191         if (rename_dst[dst_index].pair)
 192                 die("internal error: dst already matched.");
 193
 194         src = rename_src[src_index].one;
 195         one = alloc_filespec(src->path);
 196         fill_filespec(one, src->sha1, src->mode);
 197
 198         dst = rename_dst[dst_index].two;
 199         two = alloc_filespec(dst->path);
 200         fill_filespec(two, dst->sha1, dst->mode);
 201
 202         dp = diff_queue(renq, one, two);
 203         dp->score = score;
 204
 205         rename_src[src_index].src_used = 1;
 206         rename_dst[dst_index].pair = dp;
 207 }
 208
 209 /*
 210  * We sort the rename similarity matrix with the score, in descending
 211  * order (more similar first).
 212  */
 213 static int score_compare(const void *a_, const void *b_)
 214 {
 215         const struct diff_score *a = a_, *b = b_;
 216         return b->score - a->score;
 217 }
 218
 219 int diff_scoreopt_parse(const char *opt)
 220 {
 221         int diglen, num, scale, i;
 222         if (opt[0] != '-' || (opt[1] != 'M' && opt[1] != 'C'))
 223                 return -1; /* that is not a -M nor -C option */
 224         diglen = strspn(opt+2, "0123456789");
 225         if (diglen == 0 || strlen(opt+2) != diglen)
 226                 return 0; /* use default */
 227         sscanf(opt+2, "%d", &num);
 228         for (i = 0, scale = 1; i < diglen; i++)
 229                 scale *= 10;
 230
 231         /* user says num divided by scale and we say internally that
 232          * is MAX_SCORE * num / scale.
 233          */
 234         return MAX_SCORE * num / scale;
 235 }
 236
 237 void diffcore_rename(int detect_rename, int minimum_score)
 238 {
 239         struct diff_queue_struct *q = &diff_queued_diff;
 240         struct diff_queue_struct renq, outq;
 241         struct diff_score *mx;
 242         int i, j;
 243         int num_create, num_src, dst_cnt;
 244
 245         if (!minimum_score)
 246                 minimum_score = DEFAULT_MINIMUM_SCORE;
 247         renq.queue = NULL;
 248         renq.nr = renq.alloc = 0;
 249
 250         for (i = 0; i < q->nr; i++) {
 251                 struct diff_filepair *p = q->queue[i];
 252                 if (!DIFF_FILE_VALID(p->one))
 253                         if (!DIFF_FILE_VALID(p->two))
 254                                 continue; /* unmerged */
 255                         else
 256                                 locate_rename_dst(p->two, 1);
 257                 else if (!DIFF_FILE_VALID(p->two))
 258                         locate_rename_src(p->one, 1);
 259                 else if (1 < detect_rename) /* find copy, too */
 260                         locate_rename_src(p->one, 1);
 261         }
 262         if (rename_dst_nr == 0)
 263                 goto cleanup; /* nothing to do */
 264
 265         /* We really want to cull the candidates list early
 266          * with cheap tests in order to avoid doing deltas.
 267          */
 268         for (i = 0; i < rename_dst_nr; i++) {
 269                 struct diff_filespec *two = rename_dst[i].two;
 270                 for (j = 0; j < rename_src_nr; j++) {
 271                         struct diff_filespec *one = rename_src[j].one;
 272                         if (!is_exact_match(one, two))
 273                                 continue;
 274                         record_rename_pair(&renq, i, j, MAX_SCORE);
 275                         break; /* we are done with this entry */
 276                 }
 277         }
 278         diff_debug_queue("done detecting exact", &renq);
 279
 280         /* Have we run out the created file pool?  If so we can avoid
 281          * doing the delta matrix altogether.
 282          */
 283         if (renq.nr == rename_dst_nr)
 284                 goto flush_rest;
 285
 286         num_create = (rename_dst_nr - renq.nr);
 287         num_src = rename_src_nr;
 288         mx = xmalloc(sizeof(*mx) * num_create * num_src);
 289         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 290                 int base = dst_cnt * num_src;
 291                 struct diff_filespec *two = rename_dst[i].two;
 292                 if (rename_dst[i].pair)
 293                         continue; /* dealt with exact match already. */
 294                 for (j = 0; j < rename_src_nr; j++) {
 295                         struct diff_filespec *one = rename_src[j].one;
 296                         struct diff_score *m = &mx[base+j];
 297                         m->src = j;
 298                         m->dst = i;
 299                         m->score = estimate_similarity(one, two,
 300                                                        minimum_score);
 301                 }
 302                 dst_cnt++;
 303         }
 304         /* cost matrix sorted by most to least similar pair */
 305         qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
 306         for (i = 0; i < num_create * num_src; i++) {
 307                 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
 308                 if (dst->pair)
 309                         continue; /* already done, either exact or fuzzy. */
 310                 if (mx[i].score < minimum_score)
 311                         break; /* there is not any more diffs applicable. */
 312                 record_rename_pair(&renq, mx[i].dst, mx[i].src, mx[i].score);
 313         }
 314         free(mx);
 315         diff_debug_queue("done detecting fuzzy", &renq);
 316
 317  flush_rest:
 318         /* At this point, we have found some renames and copies and they
 319          * are kept in renq.  The original list is still in *q.
 320          *
 321          * Scan the original list and move them into the outq; we will sort
 322          * outq and swap it into the queue supplied to pass that to
 323          * downstream, so we assign the sort keys in this loop.
 324          *
 325          * See comments at the top of record_rename_pair for numbers used
 326          * to assign rename_rank.
 327          */
 328         outq.queue = NULL;
 329         outq.nr = outq.alloc = 0;
 330         for (i = 0; i < q->nr; i++) {
 331                 struct diff_filepair *p = q->queue[i];
 332                 struct diff_rename_src *src = locate_rename_src(p->one, 0);
 333                 struct diff_rename_dst *dst = locate_rename_dst(p->two, 0);
 334                 struct diff_filepair *pair_to_free = NULL;
 335
 336                 if (dst) {
 337                         /* creation */
 338                         if (dst->pair) {
 339                                 /* renq has rename/copy already to produce
 340                                  * this file, so we do not emit the creation
 341                                  * record in the output.
 342                                  */
 343                                 diff_q(&outq, dst->pair);
 344                                 pair_to_free = p;
 345                         }
 346                         else
 347                                 /* no matching rename/copy source, so record
 348                                  * this as a creation.
 349                                  */
 350                                 diff_q(&outq, p);
 351                 }
 352                 else if (!diff_unmodified_pair(p))
 353                         /* all the other cases need to be recorded as is */
 354                         diff_q(&outq, p);
 355                 else {
 356                         /* unmodified pair needs to be recorded only if
 357                          * it is used as the source of rename/copy
 358                          */
 359                         if (src && src->src_used)
 360                                 diff_q(&outq, p);
 361                         else
 362                                 pair_to_free = p;
 363                 }
 364                 if (pair_to_free) {
 365                         diff_free_filespec_data(pair_to_free->one);
 366                         diff_free_filespec_data(pair_to_free->two);
 367                         free(pair_to_free);
 368                 }
 369         }
 370         diff_debug_queue("done copying original", &outq);
 371
 372         free(renq.queue);
 373         free(q->queue);
 374         *q = outq;
 375         diff_debug_queue("done collapsing", q);
 376
 377  cleanup:
 378         free(rename_dst);
 379         rename_dst = NULL;
 380         rename_dst_nr = rename_dst_alloc = 0;
 381         free(rename_src);
 382         rename_src = NULL;
 383         rename_src_nr = rename_src_alloc = 0;
 384         return;
 385 }