Revert "Add deltifier test."
[git/git.git] / diffcore-break.c
CommitLineData
f345b0a0
JH
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
eeaa4603
JH
10static int should_break(struct diff_filespec *src,
11 struct diff_filespec *dst,
12 int break_score,
13 int *merge_score_p)
f345b0a0
JH
14{
15 /* dst is recorded as a modification of src. Are they so
16 * different that we are better off recording this as a pair
eeaa4603 17 * of delete and create?
f345b0a0 18 *
eeaa4603
JH
19 * There are two criteria used in this algorithm. For the
20 * purposes of helping later rename/copy, we take both delete
21 * and insert into account and estimate the amount of "edit".
22 * If the edit is very large, we break this pair so that
23 * rename/copy can pick the pieces up to match with other
24 * files.
25 *
26 * On the other hand, we would want to ignore inserts for the
27 * pure "complete rewrite" detection. As long as most of the
28 * existing contents were removed from the file, it is a
29 * complete rewrite, and if sizable chunk from the original
30 * still remains in the result, it is not a rewrite. It does
31 * not matter how much or how little new material is added to
32 * the file.
33 *
34 * The score we leave for such a broken filepair uses the
35 * latter definition so that later clean-up stage can find the
36 * pieces that should not have been broken according to the
37 * latter definition after rename/copy runs, and merge the
38 * broken pair that have a score lower than given criteria
39 * back together. The break operation itself happens
40 * according to the former definition.
41 *
42 * The minimum_edit parameter tells us when to break (the
43 * amount of "edit" required for us to consider breaking the
44 * pair). We leave the amount of deletion in *merge_score_p
45 * when we return.
46 *
47 * The value we return is 1 if we want the pair to be broken,
48 * or 0 if we do not.
f345b0a0
JH
49 */
50 void *delta;
355e76a4 51 unsigned long delta_size, base_size, src_copied, literal_added;
eeaa4603
JH
52 int to_break = 0;
53
54 *merge_score_p = 0; /* assume no deletion --- "do not break"
55 * is the default.
56 */
f345b0a0
JH
57
58 if (!S_ISREG(src->mode) || !S_ISREG(dst->mode))
59 return 0; /* leave symlink rename alone */
60
eeaa4603 61 if (diff_populate_filespec(src, 0) || diff_populate_filespec(dst, 0))
f345b0a0
JH
62 return 0; /* error but caught downstream */
63
f78c79c5 64 base_size = ((src->size < dst->size) ? src->size : dst->size);
f345b0a0 65
f345b0a0
JH
66 delta = diff_delta(src->data, src->size,
67 dst->data, dst->size,
3c849742 68 &delta_size, 0);
d28c8af6
JH
69 if (!delta)
70 return 0; /* error but caught downstream */
f345b0a0 71
f345b0a0 72 /* Estimate the edit size by interpreting delta. */
eeaa4603
JH
73 if (count_delta(delta, delta_size,
74 &src_copied, &literal_added)) {
355e76a4 75 free(delta);
eeaa4603 76 return 0; /* we cannot tell */
355e76a4 77 }
f345b0a0 78 free(delta);
355e76a4 79
eeaa4603
JH
80 /* Compute merge-score, which is "how much is removed
81 * from the source material". The clean-up stage will
82 * merge the surviving pair together if the score is
83 * less than the minimum, after rename/copy runs.
84 */
85 if (src->size <= src_copied)
f78c79c5
JH
86 ; /* all copied, nothing removed */
87 else {
eeaa4603 88 delta_size = src->size - src_copied;
f78c79c5
JH
89 *merge_score_p = delta_size * MAX_SCORE / src->size;
90 }
eeaa4603
JH
91
92 /* Extent of damage, which counts both inserts and
93 * deletes.
94 */
95 if (src->size + literal_added <= src_copied)
96 delta_size = 0; /* avoid wrapping around */
355e76a4
JH
97 else
98 delta_size = (src->size - src_copied) + literal_added;
eeaa4603
JH
99
100 /* We break if the edit exceeds the minimum.
101 * i.e. (break_score / MAX_SCORE < delta_size / base_size)
102 */
103 if (break_score * base_size < delta_size * MAX_SCORE)
104 to_break = 1;
f345b0a0 105
eeaa4603 106 return to_break;
f345b0a0
JH
107}
108
eeaa4603 109void diffcore_break(int break_score)
f345b0a0
JH
110{
111 struct diff_queue_struct *q = &diff_queued_diff;
112 struct diff_queue_struct outq;
eeaa4603
JH
113
114 /* When the filepair has this much edit (insert and delete),
115 * it is first considered to be a rewrite and broken into a
116 * create and delete filepair. This is to help breaking a
117 * file that had too much new stuff added, possibly from
118 * moving contents from another file, so that rename/copy can
119 * match it with the other file.
120 *
121 * int break_score; we reuse incoming parameter for this.
122 */
123
124 /* After a pair is broken according to break_score and
125 * subjected to rename/copy, both of them may survive intact,
126 * due to lack of suitable rename/copy peer. Or, the caller
127 * may be calling us without using rename/copy. When that
128 * happens, we merge the broken pieces back into one
129 * modification together if the pair did not have more than
130 * this much delete. For this computation, we do not take
131 * insert into account at all. If you start from a 100-line
132 * file and delete 97 lines of it, it does not matter if you
133 * add 27 lines to it to make a new 30-line file or if you add
134 * 997 lines to it to make a 1000-line file. Either way what
135 * you did was a rewrite of 97%. On the other hand, if you
136 * delete 3 lines, keeping 97 lines intact, it does not matter
137 * if you add 3 lines to it to make a new 100-line file or if
138 * you add 903 lines to it to make a new 1000-line file.
139 * Either way you did a lot of additions and not a rewrite.
140 * This merge happens to catch the latter case. A merge_score
141 * of 80% would be a good default value (a broken pair that
142 * has score lower than merge_score will be merged back
143 * together).
144 */
145 int merge_score;
f345b0a0
JH
146 int i;
147
eeaa4603
JH
148 /* See comment on DEFAULT_BREAK_SCORE and
149 * DEFAULT_MERGE_SCORE in diffcore.h
150 */
151 merge_score = (break_score >> 16) & 0xFFFF;
152 break_score = (break_score & 0xFFFF);
153
154 if (!break_score)
155 break_score = DEFAULT_BREAK_SCORE;
156 if (!merge_score)
157 merge_score = DEFAULT_MERGE_SCORE;
f345b0a0
JH
158
159 outq.nr = outq.alloc = 0;
160 outq.queue = NULL;
161
162 for (i = 0; i < q->nr; i++) {
163 struct diff_filepair *p = q->queue[i];
164 int score;
165
166 /* We deal only with in-place edit of non directory.
167 * We do not break anything else.
168 */
169 if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) &&
170 !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) &&
171 !strcmp(p->one->path, p->two->path)) {
eeaa4603 172 if (should_break(p->one, p->two,
f78c79c5
JH
173 break_score, &score) &&
174 MINIMUM_BREAK_SIZE <= p->one->size) {
f345b0a0
JH
175 /* Split this into delete and create */
176 struct diff_filespec *null_one, *null_two;
177 struct diff_filepair *dp;
178
eeaa4603
JH
179 /* Set score to 0 for the pair that
180 * needs to be merged back together
181 * should they survive rename/copy.
182 * Also we do not want to break very
183 * small files.
184 */
f78c79c5 185 if (score < merge_score)
eeaa4603
JH
186 score = 0;
187
f345b0a0
JH
188 /* deletion of one */
189 null_one = alloc_filespec(p->one->path);
190 dp = diff_queue(&outq, p->one, null_one);
191 dp->score = score;
192 dp->broken_pair = 1;
193
194 /* creation of two */
195 null_two = alloc_filespec(p->two->path);
196 dp = diff_queue(&outq, null_two, p->two);
197 dp->score = score;
198 dp->broken_pair = 1;
199
200 free(p); /* not diff_free_filepair(), we are
201 * reusing one and two here.
202 */
203 continue;
204 }
205 }
206 diff_q(&outq, p);
207 }
208 free(q->queue);
209 *q = outq;
210
211 return;
212}
eeaa4603
JH
213
214static void merge_broken(struct diff_filepair *p,
215 struct diff_filepair *pp,
216 struct diff_queue_struct *outq)
217{
218 /* p and pp are broken pairs we want to merge */
366175ef 219 struct diff_filepair *c = p, *d = pp, *dp;
eeaa4603
JH
220 if (DIFF_FILE_VALID(p->one)) {
221 /* this must be a delete half */
222 d = p; c = pp;
223 }
224 /* Sanity check */
225 if (!DIFF_FILE_VALID(d->one))
226 die("internal error in merge #1");
227 if (DIFF_FILE_VALID(d->two))
228 die("internal error in merge #2");
229 if (DIFF_FILE_VALID(c->one))
230 die("internal error in merge #3");
231 if (!DIFF_FILE_VALID(c->two))
232 die("internal error in merge #4");
233
366175ef
JH
234 dp = diff_queue(outq, d->one, c->two);
235 dp->score = p->score;
19397b45
JH
236 diff_free_filespec_data(d->two);
237 diff_free_filespec_data(c->one);
eeaa4603
JH
238 free(d);
239 free(c);
240}
241
242void diffcore_merge_broken(void)
243{
244 struct diff_queue_struct *q = &diff_queued_diff;
245 struct diff_queue_struct outq;
246 int i, j;
247
248 outq.nr = outq.alloc = 0;
249 outq.queue = NULL;
250
251 for (i = 0; i < q->nr; i++) {
252 struct diff_filepair *p = q->queue[i];
253 if (!p)
254 /* we already merged this with its peer */
255 continue;
256 else if (p->broken_pair &&
eeaa4603
JH
257 !strcmp(p->one->path, p->two->path)) {
258 /* If the peer also survived rename/copy, then
259 * we merge them back together.
260 */
261 for (j = i + 1; j < q->nr; j++) {
262 struct diff_filepair *pp = q->queue[j];
263 if (pp->broken_pair &&
eeaa4603
JH
264 !strcmp(pp->one->path, pp->two->path) &&
265 !strcmp(p->one->path, pp->two->path)) {
266 /* Peer survived. Merge them */
267 merge_broken(p, pp, &outq);
268 q->queue[j] = NULL;
269 break;
270 }
271 }
272 if (q->nr <= j)
273 /* The peer did not survive, so we keep
274 * it in the output.
275 */
276 diff_q(&outq, p);
277 }
278 else
279 diff_q(&outq, p);
280 }
281 free(q->queue);
282 *q = outq;
283
284 return;
285}