Darwin: Ignore missing /sw/lib
[git/git.git] / diffcore-break.c
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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
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10static int should_break(struct diff_filespec *src,
11 struct diff_filespec *dst,
12 int break_score,
13 int *merge_score_p)
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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 *
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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.
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49 */
50 void *delta;
355e76a4 51 unsigned long delta_size, base_size, src_copied, literal_added;
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52 int to_break = 0;
53
54 *merge_score_p = 0; /* assume no deletion --- "do not break"
55 * is the default.
56 */
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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))
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62 return 0; /* error but caught downstream */
63
f78c79c5 64 base_size = ((src->size < dst->size) ? src->size : dst->size);
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65 if (base_size < MINIMUM_BREAK_SIZE)
66 return 0; /* we do not break too small filepair */
f345b0a0 67
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68 delta = diff_delta(src->data, src->size,
69 dst->data, dst->size,
3c849742 70 &delta_size, 0);
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71 if (!delta)
72 return 0; /* error but caught downstream */
f345b0a0 73
f345b0a0 74 /* Estimate the edit size by interpreting delta. */
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75 if (count_delta(delta, delta_size,
76 &src_copied, &literal_added)) {
355e76a4 77 free(delta);
eeaa4603 78 return 0; /* we cannot tell */
355e76a4 79 }
f345b0a0 80 free(delta);
355e76a4 81
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82 /* Compute merge-score, which is "how much is removed
83 * from the source material". The clean-up stage will
84 * merge the surviving pair together if the score is
85 * less than the minimum, after rename/copy runs.
86 */
87 if (src->size <= src_copied)
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88 ; /* all copied, nothing removed */
89 else {
eeaa4603 90 delta_size = src->size - src_copied;
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91 *merge_score_p = delta_size * MAX_SCORE / src->size;
92 }
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93
94 /* Extent of damage, which counts both inserts and
95 * deletes.
96 */
97 if (src->size + literal_added <= src_copied)
98 delta_size = 0; /* avoid wrapping around */
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99 else
100 delta_size = (src->size - src_copied) + literal_added;
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101
102 /* We break if the edit exceeds the minimum.
103 * i.e. (break_score / MAX_SCORE < delta_size / base_size)
104 */
105 if (break_score * base_size < delta_size * MAX_SCORE)
106 to_break = 1;
f345b0a0 107
eeaa4603 108 return to_break;
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109}
110
eeaa4603 111void diffcore_break(int break_score)
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112{
113 struct diff_queue_struct *q = &diff_queued_diff;
114 struct diff_queue_struct outq;
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115
116 /* When the filepair has this much edit (insert and delete),
117 * it is first considered to be a rewrite and broken into a
118 * create and delete filepair. This is to help breaking a
119 * file that had too much new stuff added, possibly from
120 * moving contents from another file, so that rename/copy can
121 * match it with the other file.
122 *
123 * int break_score; we reuse incoming parameter for this.
124 */
125
126 /* After a pair is broken according to break_score and
127 * subjected to rename/copy, both of them may survive intact,
128 * due to lack of suitable rename/copy peer. Or, the caller
129 * may be calling us without using rename/copy. When that
130 * happens, we merge the broken pieces back into one
131 * modification together if the pair did not have more than
132 * this much delete. For this computation, we do not take
133 * insert into account at all. If you start from a 100-line
134 * file and delete 97 lines of it, it does not matter if you
135 * add 27 lines to it to make a new 30-line file or if you add
136 * 997 lines to it to make a 1000-line file. Either way what
137 * you did was a rewrite of 97%. On the other hand, if you
138 * delete 3 lines, keeping 97 lines intact, it does not matter
139 * if you add 3 lines to it to make a new 100-line file or if
140 * you add 903 lines to it to make a new 1000-line file.
141 * Either way you did a lot of additions and not a rewrite.
142 * This merge happens to catch the latter case. A merge_score
143 * of 80% would be a good default value (a broken pair that
144 * has score lower than merge_score will be merged back
145 * together).
146 */
147 int merge_score;
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148 int i;
149
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150 /* See comment on DEFAULT_BREAK_SCORE and
151 * DEFAULT_MERGE_SCORE in diffcore.h
152 */
153 merge_score = (break_score >> 16) & 0xFFFF;
154 break_score = (break_score & 0xFFFF);
155
156 if (!break_score)
157 break_score = DEFAULT_BREAK_SCORE;
158 if (!merge_score)
159 merge_score = DEFAULT_MERGE_SCORE;
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160
161 outq.nr = outq.alloc = 0;
162 outq.queue = NULL;
163
164 for (i = 0; i < q->nr; i++) {
165 struct diff_filepair *p = q->queue[i];
166 int score;
167
168 /* We deal only with in-place edit of non directory.
169 * We do not break anything else.
170 */
171 if (DIFF_FILE_VALID(p->one) && DIFF_FILE_VALID(p->two) &&
172 !S_ISDIR(p->one->mode) && !S_ISDIR(p->two->mode) &&
173 !strcmp(p->one->path, p->two->path)) {
eeaa4603 174 if (should_break(p->one, p->two,
0532a5e4 175 break_score, &score)) {
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176 /* Split this into delete and create */
177 struct diff_filespec *null_one, *null_two;
178 struct diff_filepair *dp;
179
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180 /* Set score to 0 for the pair that
181 * needs to be merged back together
182 * should they survive rename/copy.
183 * Also we do not want to break very
184 * small files.
185 */
f78c79c5 186 if (score < merge_score)
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187 score = 0;
188
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189 /* deletion of one */
190 null_one = alloc_filespec(p->one->path);
191 dp = diff_queue(&outq, p->one, null_one);
192 dp->score = score;
193 dp->broken_pair = 1;
194
195 /* creation of two */
196 null_two = alloc_filespec(p->two->path);
197 dp = diff_queue(&outq, null_two, p->two);
198 dp->score = score;
199 dp->broken_pair = 1;
200
201 free(p); /* not diff_free_filepair(), we are
202 * reusing one and two here.
203 */
204 continue;
205 }
206 }
207 diff_q(&outq, p);
208 }
209 free(q->queue);
210 *q = outq;
211
212 return;
213}
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214
215static void merge_broken(struct diff_filepair *p,
216 struct diff_filepair *pp,
217 struct diff_queue_struct *outq)
218{
219 /* p and pp are broken pairs we want to merge */
366175ef 220 struct diff_filepair *c = p, *d = pp, *dp;
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221 if (DIFF_FILE_VALID(p->one)) {
222 /* this must be a delete half */
223 d = p; c = pp;
224 }
225 /* Sanity check */
226 if (!DIFF_FILE_VALID(d->one))
227 die("internal error in merge #1");
228 if (DIFF_FILE_VALID(d->two))
229 die("internal error in merge #2");
230 if (DIFF_FILE_VALID(c->one))
231 die("internal error in merge #3");
232 if (!DIFF_FILE_VALID(c->two))
233 die("internal error in merge #4");
234
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235 dp = diff_queue(outq, d->one, c->two);
236 dp->score = p->score;
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237 diff_free_filespec_data(d->two);
238 diff_free_filespec_data(c->one);
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239 free(d);
240 free(c);
241}
242
243void diffcore_merge_broken(void)
244{
245 struct diff_queue_struct *q = &diff_queued_diff;
246 struct diff_queue_struct outq;
247 int i, j;
248
249 outq.nr = outq.alloc = 0;
250 outq.queue = NULL;
251
252 for (i = 0; i < q->nr; i++) {
253 struct diff_filepair *p = q->queue[i];
254 if (!p)
255 /* we already merged this with its peer */
256 continue;
257 else if (p->broken_pair &&
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258 !strcmp(p->one->path, p->two->path)) {
259 /* If the peer also survived rename/copy, then
260 * we merge them back together.
261 */
262 for (j = i + 1; j < q->nr; j++) {
263 struct diff_filepair *pp = q->queue[j];
264 if (pp->broken_pair &&
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265 !strcmp(pp->one->path, pp->two->path) &&
266 !strcmp(p->one->path, pp->two->path)) {
267 /* Peer survived. Merge them */
268 merge_broken(p, pp, &outq);
269 q->queue[j] = NULL;
270 break;
271 }
272 }
273 if (q->nr <= j)
274 /* The peer did not survive, so we keep
275 * it in the output.
276 */
277 diff_q(&outq, p);
278 }
279 else
280 diff_q(&outq, p);
281 }
282 free(q->queue);
283 *q = outq;
284
285 return;
286}