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 };
 117
 118 static int estimate_similarity(struct diff_filespec *src,
 119                                struct diff_filespec *dst,
 120                                int minimum_score)
 121 {
 122         /* src points at a file that existed in the original tree (or
 123          * optionally a file in the destination tree) and dst points
 124          * at a newly created file.  They may be quite similar, in which
 125          * case we want to say src is renamed to dst or src is copied into
 126          * dst, and then some edit has been applied to dst.
 127          *
 128          * Compare them and return how similar they are, representing
 129          * the score as an integer between 0 and 10000, except
 130          * where they match exactly it is considered better than anything
 131          * else.
 132          */
 133         void *delta;
 134         unsigned long delta_size, base_size;
 135         int score;
 136
 137         /* We deal only with regular files.  Symlink renames are handled
 138          * only when they are exact matches --- in other words, no edits
 139          * after renaming.
 140          */
 141         if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
 142                 return 0;
 143
 144         delta_size = ((src->size < dst->size) ?
 145                       (dst->size - src->size) : (src->size - dst->size));
 146         base_size = ((src->size < dst->size) ? src->size : dst->size);
 147
 148         /* We would not consider edits that change the file size so
 149          * drastically.  delta_size must be smaller than
 150          * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
 151          * Note that base_size == 0 case is handled here already
 152          * and the final score computation below would not have a
 153          * divide-by-zero issue.
 154          */
 155         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 156                 return 0;
 157
 158         delta = diff_delta(src->data, src->size,
 159                            dst->data, dst->size,
 160                            &delta_size);
 161
 162         /* A delta that has a lot of literal additions would have
 163          * big delta_size no matter what else it does.
 164          */
 165         if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
 166                 return 0;
 167
 168         /* Estimate the edit size by interpreting delta. */
 169         delta_size = count_delta(delta, delta_size);
 170         free(delta);
 171         if (delta_size == UINT_MAX)
 172                 return 0;
 173
 174         /*
 175          * Now we will give some score to it.  100% edit gets 0 points
 176          * and 0% edit gets MAX_SCORE points.
 177          */
 178         score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
 179         if (score < 0) return 0;
 180         if (MAX_SCORE < score) return MAX_SCORE;
 181         return score;
 182 }
 183
 184 static void record_rename_pair(struct diff_queue_struct *renq,
 185                                int dst_index, int src_index, int score)
 186 {
 187         struct diff_filespec *one, *two, *src, *dst;
 188         struct diff_filepair *dp;
 189
 190         if (rename_dst[dst_index].pair)
 191                 die("internal error: dst already matched.");
 192
 193         src = rename_src[src_index].one;
 194         one = alloc_filespec(src->path);
 195         fill_filespec(one, src->sha1, src->mode);
 196
 197         dst = rename_dst[dst_index].two;
 198         two = alloc_filespec(dst->path);
 199         fill_filespec(two, dst->sha1, dst->mode);
 200
 201         dp = diff_queue(renq, one, two);
 202         dp->score = score;
 203
 204         rename_src[src_index].src_used = 1;
 205         rename_dst[dst_index].pair = dp;
 206 }
 207
 208 /*
 209  * We sort the rename similarity matrix with the score, in descending
 210  * order (more similar first).
 211  */
 212 static int score_compare(const void *a_, const void *b_)
 213 {
 214         const struct diff_score *a = a_, *b = b_;
 215         return b->score - a->score;
 216 }
 217
 218 int diff_scoreopt_parse(const char *opt)
 219 {
 220         int diglen, num, scale, i;
 221         if (opt[0] != '-' || (opt[1] != 'M' && opt[1] != 'C'))
 222                 return -1; /* that is not a -M nor -C option */
 223         diglen = strspn(opt+2, "0123456789");
 224         if (diglen == 0 || strlen(opt+2) != diglen)
 225                 return 0; /* use default */
 226         sscanf(opt+2, "%d", &num);
 227         for (i = 0, scale = 1; i < diglen; i++)
 228                 scale *= 10;
 229
 230         /* user says num divided by scale and we say internally that
 231          * is MAX_SCORE * num / scale.
 232          */
 233         return MAX_SCORE * num / scale;
 234 }
 235
 236 void diffcore_rename(int detect_rename, int minimum_score)
 237 {
 238         struct diff_queue_struct *q = &diff_queued_diff;
 239         struct diff_queue_struct renq, outq;
 240         struct diff_score *mx;
 241         int i, j;
 242         int num_create, num_src, dst_cnt;
 243
 244         if (!minimum_score)
 245                 minimum_score = DEFAULT_MINIMUM_SCORE;
 246         renq.queue = NULL;
 247         renq.nr = renq.alloc = 0;
 248
 249         for (i = 0; i < q->nr; i++) {
 250                 struct diff_filepair *p = q->queue[i];
 251                 if (!DIFF_FILE_VALID(p->one))
 252                         if (!DIFF_FILE_VALID(p->two))
 253                                 continue; /* unmerged */
 254                         else
 255                                 locate_rename_dst(p->two, 1);
 256                 else if (!DIFF_FILE_VALID(p->two))
 257                         locate_rename_src(p->one, 1);
 258                 else if (1 < detect_rename) /* find copy, too */
 259                         locate_rename_src(p->one, 1);
 260         }
 261         if (rename_dst_nr == 0)
 262                 goto cleanup; /* nothing to do */
 263
 264         /* We really want to cull the candidates list early
 265          * with cheap tests in order to avoid doing deltas.
 266          */
 267         for (i = 0; i < rename_dst_nr; i++) {
 268                 struct diff_filespec *two = rename_dst[i].two;
 269                 for (j = 0; j < rename_src_nr; j++) {
 270                         struct diff_filespec *one = rename_src[j].one;
 271                         if (!is_exact_match(one, two))
 272                                 continue;
 273                         record_rename_pair(&renq, i, j, MAX_SCORE);
 274                         break; /* we are done with this entry */
 275                 }
 276         }
 277         diff_debug_queue("done detecting exact", &renq);
 278
 279         /* Have we run out the created file pool?  If so we can avoid
 280          * doing the delta matrix altogether.
 281          */
 282         if (renq.nr == rename_dst_nr)
 283                 goto flush_rest;
 284
 285         num_create = (rename_dst_nr - renq.nr);
 286         num_src = rename_src_nr;
 287         mx = xmalloc(sizeof(*mx) * num_create * num_src);
 288         for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
 289                 int base = dst_cnt * num_src;
 290                 struct diff_filespec *two = rename_dst[i].two;
 291                 if (rename_dst[i].pair)
 292                         continue; /* dealt with exact match already. */
 293                 for (j = 0; j < rename_src_nr; j++) {
 294                         struct diff_filespec *one = rename_src[j].one;
 295                         struct diff_score *m = &mx[base+j];
 296                         m->src = j;
 297                         m->dst = i;
 298                         m->score = estimate_similarity(one, two,
 299                                                        minimum_score);
 300                 }
 301                 dst_cnt++;
 302         }
 303         /* cost matrix sorted by most to least similar pair */
 304         qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
 305         for (i = 0; i < num_create * num_src; i++) {
 306                 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
 307                 if (dst->pair)
 308                         continue; /* already done, either exact or fuzzy. */
 309                 if (mx[i].score < minimum_score)
 310                         break; /* there is not any more diffs applicable. */
 311                 record_rename_pair(&renq, mx[i].dst, mx[i].src, mx[i].score);
 312         }
 313         free(mx);
 314         diff_debug_queue("done detecting fuzzy", &renq);
 315
 316  flush_rest:
 317         /* At this point, we have found some renames and copies and they
 318          * are kept in renq.  The original list is still in *q.
 319          *
 320          * Scan the original list and move them into the outq; we will sort
 321          * outq and swap it into the queue supplied to pass that to
 322          * downstream, so we assign the sort keys in this loop.
 323          *
 324          * See comments at the top of record_rename_pair for numbers used
 325          * to assign rename_rank.
 326          */
 327         outq.queue = NULL;
 328         outq.nr = outq.alloc = 0;
 329         for (i = 0; i < q->nr; i++) {
 330                 struct diff_filepair *p = q->queue[i];
 331                 struct diff_rename_src *src = locate_rename_src(p->one, 0);
 332                 struct diff_rename_dst *dst = locate_rename_dst(p->two, 0);
 333                 struct diff_filepair *pair_to_free = NULL;
 334
 335                 if (dst) {
 336                         /* creation */
 337                         if (dst->pair) {
 338                                 /* renq has rename/copy already to produce
 339                                  * this file, so we do not emit the creation
 340                                  * record in the output.
 341                                  */
 342                                 diff_q(&outq, dst->pair);
 343                                 pair_to_free = p;
 344                         }
 345                         else
 346                                 /* no matching rename/copy source, so record
 347                                  * this as a creation.
 348                                  */
 349                                 diff_q(&outq, p);
 350                 }
 351                 else if (!diff_unmodified_pair(p))
 352                         /* all the other cases need to be recorded as is */
 353                         diff_q(&outq, p);
 354                 else {
 355                         /* unmodified pair needs to be recorded only if
 356                          * it is used as the source of rename/copy
 357                          */
 358                         if (src && src->src_used)
 359                                 diff_q(&outq, p);
 360                         else
 361                                 pair_to_free = p;
 362                 }
 363                 if (pair_to_free)
 364                         diff_free_filepair(pair_to_free);
 365         }
 366         diff_debug_queue("done copying original", &outq);
 367
 368         free(renq.queue);
 369         free(q->queue);
 370         *q = outq;
 371         diff_debug_queue("done collapsing", q);
 372
 373  cleanup:
 374         free(rename_dst);
 375         rename_dst = NULL;
 376         rename_dst_nr = rename_dst_alloc = 0;
 377         free(rename_src);
 378         rename_src = NULL;
 379         rename_src_nr = rename_src_alloc = 0;
 380         return;
 381 }