Merge branch 'rb/hpe'
[git.git] / xdiff / xpatience.c
blobf3573d9f00e77ab551b7f109f29356721165ff47
1 /*
2 * LibXDiff by Davide Libenzi ( File Differential Library )
3 * Copyright (C) 2003-2016 Davide Libenzi, Johannes E. Schindelin
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; either
8 * version 2.1 of the License, or (at your option) any later version.
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, see
17 * <http://www.gnu.org/licenses/>.
19 * Davide Libenzi <davidel@xmailserver.org>
22 #include "xinclude.h"
23 #include "xtypes.h"
24 #include "xdiff.h"
27 * The basic idea of patience diff is to find lines that are unique in
28 * both files. These are intuitively the ones that we want to see as
29 * common lines.
31 * The maximal ordered sequence of such line pairs (where ordered means
32 * that the order in the sequence agrees with the order of the lines in
33 * both files) naturally defines an initial set of common lines.
35 * Now, the algorithm tries to extend the set of common lines by growing
36 * the line ranges where the files have identical lines.
38 * Between those common lines, the patience diff algorithm is applied
39 * recursively, until no unique line pairs can be found; these line ranges
40 * are handled by the well-known Myers algorithm.
43 #define NON_UNIQUE ULONG_MAX
46 * This is a hash mapping from line hash to line numbers in the first and
47 * second file.
49 struct hashmap {
50 int nr, alloc;
51 struct entry {
52 unsigned long hash;
54 * 0 = unused entry, 1 = first line, 2 = second, etc.
55 * line2 is NON_UNIQUE if the line is not unique
56 * in either the first or the second file.
58 unsigned long line1, line2;
60 * "next" & "previous" are used for the longest common
61 * sequence;
62 * initially, "next" reflects only the order in file1.
64 struct entry *next, *previous;
67 * If 1, this entry can serve as an anchor. See
68 * Documentation/diff-options.txt for more information.
70 unsigned anchor : 1;
71 } *entries, *first, *last;
72 /* were common records found? */
73 unsigned long has_matches;
74 mmfile_t *file1, *file2;
75 xdfenv_t *env;
76 xpparam_t const *xpp;
79 static int is_anchor(xpparam_t const *xpp, const char *line)
81 int i;
82 for (i = 0; i < xpp->anchors_nr; i++) {
83 if (!strncmp(line, xpp->anchors[i], strlen(xpp->anchors[i])))
84 return 1;
86 return 0;
89 /* The argument "pass" is 1 for the first file, 2 for the second. */
90 static void insert_record(xpparam_t const *xpp, int line, struct hashmap *map,
91 int pass)
93 xrecord_t **records = pass == 1 ?
94 map->env->xdf1.recs : map->env->xdf2.recs;
95 xrecord_t *record = records[line - 1], *other;
97 * After xdl_prepare_env() (or more precisely, due to
98 * xdl_classify_record()), the "ha" member of the records (AKA lines)
99 * is _not_ the hash anymore, but a linearized version of it. In
100 * other words, the "ha" member is guaranteed to start with 0 and
101 * the second record's ha can only be 0 or 1, etc.
103 * So we multiply ha by 2 in the hope that the hashing was
104 * "unique enough".
106 int index = (int)((record->ha << 1) % map->alloc);
108 while (map->entries[index].line1) {
109 other = map->env->xdf1.recs[map->entries[index].line1 - 1];
110 if (map->entries[index].hash != record->ha ||
111 !xdl_recmatch(record->ptr, record->size,
112 other->ptr, other->size,
113 map->xpp->flags)) {
114 if (++index >= map->alloc)
115 index = 0;
116 continue;
118 if (pass == 2)
119 map->has_matches = 1;
120 if (pass == 1 || map->entries[index].line2)
121 map->entries[index].line2 = NON_UNIQUE;
122 else
123 map->entries[index].line2 = line;
124 return;
126 if (pass == 2)
127 return;
128 map->entries[index].line1 = line;
129 map->entries[index].hash = record->ha;
130 map->entries[index].anchor = is_anchor(xpp, map->env->xdf1.recs[line - 1]->ptr);
131 if (!map->first)
132 map->first = map->entries + index;
133 if (map->last) {
134 map->last->next = map->entries + index;
135 map->entries[index].previous = map->last;
137 map->last = map->entries + index;
138 map->nr++;
142 * This function has to be called for each recursion into the inter-hunk
143 * parts, as previously non-unique lines can become unique when being
144 * restricted to a smaller part of the files.
146 * It is assumed that env has been prepared using xdl_prepare().
148 static int fill_hashmap(mmfile_t *file1, mmfile_t *file2,
149 xpparam_t const *xpp, xdfenv_t *env,
150 struct hashmap *result,
151 int line1, int count1, int line2, int count2)
153 result->file1 = file1;
154 result->file2 = file2;
155 result->xpp = xpp;
156 result->env = env;
158 /* We know exactly how large we want the hash map */
159 result->alloc = count1 * 2;
160 result->entries = (struct entry *)
161 xdl_malloc(result->alloc * sizeof(struct entry));
162 if (!result->entries)
163 return -1;
164 memset(result->entries, 0, result->alloc * sizeof(struct entry));
166 /* First, fill with entries from the first file */
167 while (count1--)
168 insert_record(xpp, line1++, result, 1);
170 /* Then search for matches in the second file */
171 while (count2--)
172 insert_record(xpp, line2++, result, 2);
174 return 0;
178 * Find the longest sequence with a smaller last element (meaning a smaller
179 * line2, as we construct the sequence with entries ordered by line1).
181 static int binary_search(struct entry **sequence, int longest,
182 struct entry *entry)
184 int left = -1, right = longest;
186 while (left + 1 < right) {
187 int middle = left + (right - left) / 2;
188 /* by construction, no two entries can be equal */
189 if (sequence[middle]->line2 > entry->line2)
190 right = middle;
191 else
192 left = middle;
194 /* return the index in "sequence", _not_ the sequence length */
195 return left;
199 * The idea is to start with the list of common unique lines sorted by
200 * the order in file1. For each of these pairs, the longest (partial)
201 * sequence whose last element's line2 is smaller is determined.
203 * For efficiency, the sequences are kept in a list containing exactly one
204 * item per sequence length: the sequence with the smallest last
205 * element (in terms of line2).
207 static struct entry *find_longest_common_sequence(struct hashmap *map)
209 struct entry **sequence = xdl_malloc(map->nr * sizeof(struct entry *));
210 int longest = 0, i;
211 struct entry *entry;
214 * If not -1, this entry in sequence must never be overridden.
215 * Therefore, overriding entries before this has no effect, so
216 * do not do that either.
218 int anchor_i = -1;
220 for (entry = map->first; entry; entry = entry->next) {
221 if (!entry->line2 || entry->line2 == NON_UNIQUE)
222 continue;
223 i = binary_search(sequence, longest, entry);
224 entry->previous = i < 0 ? NULL : sequence[i];
225 ++i;
226 if (i <= anchor_i)
227 continue;
228 sequence[i] = entry;
229 if (entry->anchor) {
230 anchor_i = i;
231 longest = anchor_i + 1;
232 } else if (i == longest) {
233 longest++;
237 /* No common unique lines were found */
238 if (!longest) {
239 xdl_free(sequence);
240 return NULL;
243 /* Iterate starting at the last element, adjusting the "next" members */
244 entry = sequence[longest - 1];
245 entry->next = NULL;
246 while (entry->previous) {
247 entry->previous->next = entry;
248 entry = entry->previous;
250 xdl_free(sequence);
251 return entry;
254 static int match(struct hashmap *map, int line1, int line2)
256 xrecord_t *record1 = map->env->xdf1.recs[line1 - 1];
257 xrecord_t *record2 = map->env->xdf2.recs[line2 - 1];
258 return xdl_recmatch(record1->ptr, record1->size,
259 record2->ptr, record2->size, map->xpp->flags);
262 static int patience_diff(mmfile_t *file1, mmfile_t *file2,
263 xpparam_t const *xpp, xdfenv_t *env,
264 int line1, int count1, int line2, int count2);
266 static int walk_common_sequence(struct hashmap *map, struct entry *first,
267 int line1, int count1, int line2, int count2)
269 int end1 = line1 + count1, end2 = line2 + count2;
270 int next1, next2;
272 for (;;) {
273 /* Try to grow the line ranges of common lines */
274 if (first) {
275 next1 = first->line1;
276 next2 = first->line2;
277 while (next1 > line1 && next2 > line2 &&
278 match(map, next1 - 1, next2 - 1)) {
279 next1--;
280 next2--;
282 } else {
283 next1 = end1;
284 next2 = end2;
286 while (line1 < next1 && line2 < next2 &&
287 match(map, line1, line2)) {
288 line1++;
289 line2++;
292 /* Recurse */
293 if (next1 > line1 || next2 > line2) {
294 struct hashmap submap;
296 memset(&submap, 0, sizeof(submap));
297 if (patience_diff(map->file1, map->file2,
298 map->xpp, map->env,
299 line1, next1 - line1,
300 line2, next2 - line2))
301 return -1;
304 if (!first)
305 return 0;
307 while (first->next &&
308 first->next->line1 == first->line1 + 1 &&
309 first->next->line2 == first->line2 + 1)
310 first = first->next;
312 line1 = first->line1 + 1;
313 line2 = first->line2 + 1;
315 first = first->next;
319 static int fall_back_to_classic_diff(struct hashmap *map,
320 int line1, int count1, int line2, int count2)
322 xpparam_t xpp;
323 xpp.flags = map->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
325 return xdl_fall_back_diff(map->env, &xpp,
326 line1, count1, line2, count2);
330 * Recursively find the longest common sequence of unique lines,
331 * and if none was found, ask xdl_do_diff() to do the job.
333 * This function assumes that env was prepared with xdl_prepare_env().
335 static int patience_diff(mmfile_t *file1, mmfile_t *file2,
336 xpparam_t const *xpp, xdfenv_t *env,
337 int line1, int count1, int line2, int count2)
339 struct hashmap map;
340 struct entry *first;
341 int result = 0;
343 /* trivial case: one side is empty */
344 if (!count1) {
345 while(count2--)
346 env->xdf2.rchg[line2++ - 1] = 1;
347 return 0;
348 } else if (!count2) {
349 while(count1--)
350 env->xdf1.rchg[line1++ - 1] = 1;
351 return 0;
354 memset(&map, 0, sizeof(map));
355 if (fill_hashmap(file1, file2, xpp, env, &map,
356 line1, count1, line2, count2))
357 return -1;
359 /* are there any matching lines at all? */
360 if (!map.has_matches) {
361 while(count1--)
362 env->xdf1.rchg[line1++ - 1] = 1;
363 while(count2--)
364 env->xdf2.rchg[line2++ - 1] = 1;
365 xdl_free(map.entries);
366 return 0;
369 first = find_longest_common_sequence(&map);
370 if (first)
371 result = walk_common_sequence(&map, first,
372 line1, count1, line2, count2);
373 else
374 result = fall_back_to_classic_diff(&map,
375 line1, count1, line2, count2);
377 xdl_free(map.entries);
378 return result;
381 int xdl_do_patience_diff(mmfile_t *file1, mmfile_t *file2,
382 xpparam_t const *xpp, xdfenv_t *env)
384 if (xdl_prepare_env(file1, file2, xpp, env) < 0)
385 return -1;
387 /* environment is cleaned up in xdl_diff() */
388 return patience_diff(file1, file2, xpp, env,
389 1, env->xdf1.nrec, 1, env->xdf2.nrec);