diffcore-rename: split out the delta counting code.
[git/git.git] / 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 }