Fix delta "sliding window" 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 #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_stays : 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_stays)
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_stays = src_stays;
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 int score;
140
141 /* We deal only with regular files. Symlink renames are handled
142 * only when they are exact matches --- in other words, no edits
143 * after renaming.
144 */
145 if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
146 return 0;
147
148 delta_size = ((src->size < dst->size) ?
149 (dst->size - src->size) : (src->size - dst->size));
150 base_size = ((src->size < dst->size) ? src->size : dst->size);
151
152 /* We would not consider edits that change the file size so
153 * drastically. delta_size must be smaller than
154 * (MAX_SCORE-minimum_score)/MAX_SCORE * min(src->size, dst->size).
155 *
156 * Note that base_size == 0 case is handled here already
157 * and the final score computation below would not have a
158 * divide-by-zero issue.
159 */
160 if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
161 return 0;
162
163 if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
164 return 0; /* error but caught downstream */
165
166 delta = diff_delta(src->data, src->size,
167 dst->data, dst->size,
168 &delta_size);
169
170 /* A delta that has a lot of literal additions would have
171 * big delta_size no matter what else it does.
172 */
173 if (base_size * (MAX_SCORE-minimum_score) < delta_size * MAX_SCORE)
174 return 0;
175
176 /* Estimate the edit size by interpreting delta. */
177 if (count_delta(delta, delta_size, &src_copied, &literal_added)) {
178 free(delta);
179 return 0;
180 }
181 free(delta);
182
183 /* Extent of damage */
184 if (src->size + literal_added < src_copied)
185 delta_size = 0;
186 else
187 delta_size = (src->size - src_copied) + literal_added;
188
189 /*
190 * Now we will give some score to it. 100% edit gets 0 points
191 * and 0% edit gets MAX_SCORE points.
192 */
193 score = MAX_SCORE - (MAX_SCORE * delta_size / base_size);
194 if (score < 0) return 0;
195 if (MAX_SCORE < score) return MAX_SCORE;
196 return score;
197 }
198
199 static void record_rename_pair(struct diff_queue_struct *renq,
200 int dst_index, int src_index, int score)
201 {
202 struct diff_filespec *one, *two, *src, *dst;
203 struct diff_filepair *dp;
204
205 if (rename_dst[dst_index].pair)
206 die("internal error: dst already matched.");
207
208 src = rename_src[src_index].one;
209 one = alloc_filespec(src->path);
210 fill_filespec(one, src->sha1, src->mode);
211
212 dst = rename_dst[dst_index].two;
213 two = alloc_filespec(dst->path);
214 fill_filespec(two, dst->sha1, dst->mode);
215
216 dp = diff_queue(renq, one, two);
217 dp->score = score;
218 dp->source_stays = rename_src[src_index].src_stays;
219 rename_dst[dst_index].pair = dp;
220 }
221
222 /*
223 * We sort the rename similarity matrix with the score, in descending
224 * order (the most similar first).
225 */
226 static int score_compare(const void *a_, const void *b_)
227 {
228 const struct diff_score *a = a_, *b = b_;
229 return b->score - a->score;
230 }
231
232 void diffcore_rename(int detect_rename, int minimum_score)
233 {
234 struct diff_queue_struct *q = &diff_queued_diff;
235 struct diff_queue_struct renq, outq;
236 struct diff_score *mx;
237 int i, j;
238 int num_create, num_src, dst_cnt;
239
240 if (!minimum_score)
241 minimum_score = DEFAULT_RENAME_SCORE;
242 renq.queue = NULL;
243 renq.nr = renq.alloc = 0;
244
245 for (i = 0; i < q->nr; i++) {
246 struct diff_filepair *p = q->queue[i];
247 if (!DIFF_FILE_VALID(p->one))
248 if (!DIFF_FILE_VALID(p->two))
249 continue; /* unmerged */
250 else
251 locate_rename_dst(p->two, 1);
252 else if (!DIFF_FILE_VALID(p->two)) {
253 /* If the source is a broken "delete", and
254 * they did not really want to get broken,
255 * that means the source actually stays.
256 */
257 int stays = (p->broken_pair && !p->score);
258 register_rename_src(p->one, stays);
259 }
260 else if (detect_rename == DIFF_DETECT_COPY)
261 register_rename_src(p->one, 1);
262 }
263 if (rename_dst_nr == 0)
264 goto cleanup; /* nothing to do */
265
266 /* We really want to cull the candidates list early
267 * with cheap tests in order to avoid doing deltas.
268 */
269 for (i = 0; i < rename_dst_nr; i++) {
270 struct diff_filespec *two = rename_dst[i].two;
271 for (j = 0; j < rename_src_nr; j++) {
272 struct diff_filespec *one = rename_src[j].one;
273 if (!is_exact_match(one, two))
274 continue;
275 record_rename_pair(&renq, i, j, MAX_SCORE);
276 break; /* we are done with this entry */
277 }
278 }
279 diff_debug_queue("done detecting exact", &renq);
280
281 /* Have we run out the created file pool? If so we can avoid
282 * doing the delta matrix altogether.
283 */
284 if (renq.nr == rename_dst_nr)
285 goto cleanup;
286
287 num_create = (rename_dst_nr - renq.nr);
288 num_src = rename_src_nr;
289 mx = xmalloc(sizeof(*mx) * num_create * num_src);
290 for (dst_cnt = i = 0; i < rename_dst_nr; i++) {
291 int base = dst_cnt * num_src;
292 struct diff_filespec *two = rename_dst[i].two;
293 if (rename_dst[i].pair)
294 continue; /* dealt with exact match already. */
295 for (j = 0; j < rename_src_nr; j++) {
296 struct diff_filespec *one = rename_src[j].one;
297 struct diff_score *m = &mx[base+j];
298 m->src = j;
299 m->dst = i;
300 m->score = estimate_similarity(one, two,
301 minimum_score);
302 }
303 dst_cnt++;
304 }
305 /* cost matrix sorted by most to least similar pair */
306 qsort(mx, num_create * num_src, sizeof(*mx), score_compare);
307 for (i = 0; i < num_create * num_src; i++) {
308 struct diff_rename_dst *dst = &rename_dst[mx[i].dst];
309 if (dst->pair)
310 continue; /* already done, either exact or fuzzy. */
311 if (mx[i].score < minimum_score)
312 break; /* there is no more usable pair. */
313 record_rename_pair(&renq, mx[i].dst, mx[i].src, mx[i].score);
314 }
315 free(mx);
316 diff_debug_queue("done detecting fuzzy", &renq);
317
318 cleanup:
319 /* At this point, we have found some renames and copies and they
320 * are kept in renq. The original list is still in *q.
321 */
322 outq.queue = NULL;
323 outq.nr = outq.alloc = 0;
324 for (i = 0; i < q->nr; i++) {
325 struct diff_filepair *p = q->queue[i];
326 struct diff_filepair *pair_to_free = NULL;
327
328 if (!DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two)) {
329 /*
330 * Creation
331 *
332 * We would output this create record if it has
333 * not been turned into a rename/copy already.
334 */
335 struct diff_rename_dst *dst =
336 locate_rename_dst(p->two, 0);
337 if (dst && dst->pair) {
338 diff_q(&outq, dst->pair);
339 pair_to_free = p;
340 }
341 else
342 /* no matching rename/copy source, so
343 * record this as a creation.
344 */
345 diff_q(&outq, p);
346 }
347 else if (DIFF_FILE_VALID(p->one) && !DIFF_FILE_VALID(p->two)) {
348 /*
349 * Deletion
350 *
351 * We would output this delete record if:
352 *
353 * (1) this is a broken delete and the counterpart
354 * broken create remains in the output; or
355 * (2) this is not a broken delete, and renq does
356 * not have a rename/copy to move p->one->path
357 * out.
358 *
359 * Otherwise, the counterpart broken create
360 * has been turned into a rename-edit; or
361 * delete did not have a matching create to
362 * begin with.
363 */
364 if (DIFF_PAIR_BROKEN(p)) {
365 /* broken delete */
366 struct diff_rename_dst *dst =
367 locate_rename_dst(p->one, 0);
368 if (dst && dst->pair)
369 /* counterpart is now rename/copy */
370 pair_to_free = p;
371 }
372 else {
373 for (j = 0; j < renq.nr; j++)
374 if (!strcmp(renq.queue[j]->one->path,
375 p->one->path))
376 break;
377 if (j < renq.nr)
378 /* this path remains */
379 pair_to_free = p;
380 }
381
382 if (pair_to_free)
383 ;
384 else
385 diff_q(&outq, p);
386 }
387 else if (!diff_unmodified_pair(p))
388 /* all the usual ones need to be kept */
389 diff_q(&outq, p);
390 else
391 /* no need to keep unmodified pairs */
392 pair_to_free = p;
393
394 if (pair_to_free)
395 diff_free_filepair(pair_to_free);
396 }
397 diff_debug_queue("done copying original", &outq);
398
399 free(renq.queue);
400 free(q->queue);
401 *q = outq;
402 diff_debug_queue("done collapsing", q);
403
404 free(rename_dst);
405 rename_dst = NULL;
406 rename_dst_nr = rename_dst_alloc = 0;
407 free(rename_src);
408 rename_src = NULL;
409 rename_src_nr = rename_src_alloc = 0;
410 return;
411 }