Merge branch 'pk/subsub-fetch-fix'
[git] / xdiff / xhistogram.c
1 /*
2  * Copyright (C) 2010, Google Inc.
3  * and other copyright owners as documented in JGit's IP log.
4  *
5  * This program and the accompanying materials are made available
6  * under the terms of the Eclipse Distribution License v1.0 which
7  * accompanies this distribution, is reproduced below, and is
8  * available at http://www.eclipse.org/org/documents/edl-v10.php
9  *
10  * All rights reserved.
11  *
12  * Redistribution and use in source and binary forms, with or
13  * without modification, are permitted provided that the following
14  * conditions are met:
15  *
16  * - Redistributions of source code must retain the above copyright
17  *   notice, this list of conditions and the following disclaimer.
18  *
19  * - Redistributions in binary form must reproduce the above
20  *   copyright notice, this list of conditions and the following
21  *   disclaimer in the documentation and/or other materials provided
22  *   with the distribution.
23  *
24  * - Neither the name of the Eclipse Foundation, Inc. nor the
25  *   names of its contributors may be used to endorse or promote
26  *   products derived from this software without specific prior
27  *   written permission.
28  *
29  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
30  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
31  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
33  * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
34  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
35  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
36  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
37  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
38  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
40  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
41  * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
42  */
43
44 #include "xinclude.h"
45
46 #define MAX_PTR UINT_MAX
47 #define MAX_CNT UINT_MAX
48
49 #define LINE_END(n) (line##n + count##n - 1)
50 #define LINE_END_PTR(n) (*line##n + *count##n - 1)
51
52 struct histindex {
53         struct record {
54                 unsigned int ptr, cnt;
55                 struct record *next;
56         } **records, /* an occurrence */
57           **line_map; /* map of line to record chain */
58         chastore_t rcha;
59         unsigned int *next_ptrs;
60         unsigned int table_bits,
61                      records_size,
62                      line_map_size;
63
64         unsigned int max_chain_length,
65                      key_shift,
66                      ptr_shift;
67
68         unsigned int cnt,
69                      has_common;
70
71         xdfenv_t *env;
72         xpparam_t const *xpp;
73 };
74
75 struct region {
76         unsigned int begin1, end1;
77         unsigned int begin2, end2;
78 };
79
80 #define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
81
82 #define NEXT_PTR(index, ptr) \
83         (index->next_ptrs[(ptr) - index->ptr_shift])
84
85 #define CNT(index, ptr) \
86         ((LINE_MAP(index, ptr))->cnt)
87
88 #define REC(env, s, l) \
89         (env->xdf##s.recs[l - 1])
90
91 static int cmp_recs(xpparam_t const *xpp,
92         xrecord_t *r1, xrecord_t *r2)
93 {
94         return r1->ha == r2->ha &&
95                 xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
96                             xpp->flags);
97 }
98
99 #define CMP_ENV(xpp, env, s1, l1, s2, l2) \
100         (cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
101
102 #define CMP(i, s1, l1, s2, l2) \
103         (cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
104
105 #define TABLE_HASH(index, side, line) \
106         XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
107
108 static int scanA(struct histindex *index, int line1, int count1)
109 {
110         unsigned int ptr, tbl_idx;
111         unsigned int chain_len;
112         struct record **rec_chain, *rec;
113
114         for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
115                 tbl_idx = TABLE_HASH(index, 1, ptr);
116                 rec_chain = index->records + tbl_idx;
117                 rec = *rec_chain;
118
119                 chain_len = 0;
120                 while (rec) {
121                         if (CMP(index, 1, rec->ptr, 1, ptr)) {
122                                 /*
123                                  * ptr is identical to another element. Insert
124                                  * it onto the front of the existing element
125                                  * chain.
126                                  */
127                                 NEXT_PTR(index, ptr) = rec->ptr;
128                                 rec->ptr = ptr;
129                                 /* cap rec->cnt at MAX_CNT */
130                                 rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
131                                 LINE_MAP(index, ptr) = rec;
132                                 goto continue_scan;
133                         }
134
135                         rec = rec->next;
136                         chain_len++;
137                 }
138
139                 if (chain_len == index->max_chain_length)
140                         return -1;
141
142                 /*
143                  * This is the first time we have ever seen this particular
144                  * element in the sequence. Construct a new chain for it.
145                  */
146                 if (!(rec = xdl_cha_alloc(&index->rcha)))
147                         return -1;
148                 rec->ptr = ptr;
149                 rec->cnt = 1;
150                 rec->next = *rec_chain;
151                 *rec_chain = rec;
152                 LINE_MAP(index, ptr) = rec;
153
154 continue_scan:
155                 ; /* no op */
156         }
157
158         return 0;
159 }
160
161 static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
162         int line1, int count1, int line2, int count2)
163 {
164         unsigned int b_next = b_ptr + 1;
165         struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
166         unsigned int as, ae, bs, be, np, rc;
167         int should_break;
168
169         for (; rec; rec = rec->next) {
170                 if (rec->cnt > index->cnt) {
171                         if (!index->has_common)
172                                 index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
173                         continue;
174                 }
175
176                 as = rec->ptr;
177                 if (!CMP(index, 1, as, 2, b_ptr))
178                         continue;
179
180                 index->has_common = 1;
181                 for (;;) {
182                         should_break = 0;
183                         np = NEXT_PTR(index, as);
184                         bs = b_ptr;
185                         ae = as;
186                         be = bs;
187                         rc = rec->cnt;
188
189                         while (line1 < as && line2 < bs
190                                 && CMP(index, 1, as - 1, 2, bs - 1)) {
191                                 as--;
192                                 bs--;
193                                 if (1 < rc)
194                                         rc = XDL_MIN(rc, CNT(index, as));
195                         }
196                         while (ae < LINE_END(1) && be < LINE_END(2)
197                                 && CMP(index, 1, ae + 1, 2, be + 1)) {
198                                 ae++;
199                                 be++;
200                                 if (1 < rc)
201                                         rc = XDL_MIN(rc, CNT(index, ae));
202                         }
203
204                         if (b_next <= be)
205                                 b_next = be + 1;
206                         if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
207                                 lcs->begin1 = as;
208                                 lcs->begin2 = bs;
209                                 lcs->end1 = ae;
210                                 lcs->end2 = be;
211                                 index->cnt = rc;
212                         }
213
214                         if (np == 0)
215                                 break;
216
217                         while (np <= ae) {
218                                 np = NEXT_PTR(index, np);
219                                 if (np == 0) {
220                                         should_break = 1;
221                                         break;
222                                 }
223                         }
224
225                         if (should_break)
226                                 break;
227
228                         as = np;
229                 }
230         }
231         return b_next;
232 }
233
234 static int fall_back_to_classic_diff(xpparam_t const *xpp, xdfenv_t *env,
235                 int line1, int count1, int line2, int count2)
236 {
237         xpparam_t xpparam;
238
239         memset(&xpparam, 0, sizeof(xpparam));
240         xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
241
242         return xdl_fall_back_diff(env, &xpparam,
243                                   line1, count1, line2, count2);
244 }
245
246 static inline void free_index(struct histindex *index)
247 {
248         xdl_free(index->records);
249         xdl_free(index->line_map);
250         xdl_free(index->next_ptrs);
251         xdl_cha_free(&index->rcha);
252 }
253
254 static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
255                     struct region *lcs,
256                     int line1, int count1, int line2, int count2)
257 {
258         int b_ptr;
259         int sz, ret = -1;
260         struct histindex index;
261
262         memset(&index, 0, sizeof(index));
263
264         index.env = env;
265         index.xpp = xpp;
266
267         index.records = NULL;
268         index.line_map = NULL;
269         /* in case of early xdl_cha_free() */
270         index.rcha.head = NULL;
271
272         index.table_bits = xdl_hashbits(count1);
273         sz = index.records_size = 1 << index.table_bits;
274         sz *= sizeof(struct record *);
275         if (!(index.records = (struct record **) xdl_malloc(sz)))
276                 goto cleanup;
277         memset(index.records, 0, sz);
278
279         sz = index.line_map_size = count1;
280         sz *= sizeof(struct record *);
281         if (!(index.line_map = (struct record **) xdl_malloc(sz)))
282                 goto cleanup;
283         memset(index.line_map, 0, sz);
284
285         sz = index.line_map_size;
286         sz *= sizeof(unsigned int);
287         if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
288                 goto cleanup;
289         memset(index.next_ptrs, 0, sz);
290
291         /* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
292         if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
293                 goto cleanup;
294
295         index.ptr_shift = line1;
296         index.max_chain_length = 64;
297
298         if (scanA(&index, line1, count1))
299                 goto cleanup;
300
301         index.cnt = index.max_chain_length + 1;
302
303         for (b_ptr = line2; b_ptr <= LINE_END(2); )
304                 b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);
305
306         if (index.has_common && index.max_chain_length < index.cnt)
307                 ret = 1;
308         else
309                 ret = 0;
310
311 cleanup:
312         free_index(&index);
313         return ret;
314 }
315
316 static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
317         int line1, int count1, int line2, int count2)
318 {
319         struct region lcs;
320         int lcs_found;
321         int result;
322 redo:
323         result = -1;
324
325         if (count1 <= 0 && count2 <= 0)
326                 return 0;
327
328         if (LINE_END(1) >= MAX_PTR)
329                 return -1;
330
331         if (!count1) {
332                 while(count2--)
333                         env->xdf2.rchg[line2++ - 1] = 1;
334                 return 0;
335         } else if (!count2) {
336                 while(count1--)
337                         env->xdf1.rchg[line1++ - 1] = 1;
338                 return 0;
339         }
340
341         memset(&lcs, 0, sizeof(lcs));
342         lcs_found = find_lcs(xpp, env, &lcs, line1, count1, line2, count2);
343         if (lcs_found < 0)
344                 goto out;
345         else if (lcs_found)
346                 result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
347         else {
348                 if (lcs.begin1 == 0 && lcs.begin2 == 0) {
349                         while (count1--)
350                                 env->xdf1.rchg[line1++ - 1] = 1;
351                         while (count2--)
352                                 env->xdf2.rchg[line2++ - 1] = 1;
353                         result = 0;
354                 } else {
355                         result = histogram_diff(xpp, env,
356                                                 line1, lcs.begin1 - line1,
357                                                 line2, lcs.begin2 - line2);
358                         if (result)
359                                 goto out;
360                         /*
361                          * result = histogram_diff(xpp, env,
362                          *            lcs.end1 + 1, LINE_END(1) - lcs.end1,
363                          *            lcs.end2 + 1, LINE_END(2) - lcs.end2);
364                          * but let's optimize tail recursion ourself:
365                         */
366                         count1 = LINE_END(1) - lcs.end1;
367                         line1 = lcs.end1 + 1;
368                         count2 = LINE_END(2) - lcs.end2;
369                         line2 = lcs.end2 + 1;
370                         goto redo;
371                 }
372         }
373 out:
374         return result;
375 }
376
377 int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
378         xpparam_t const *xpp, xdfenv_t *env)
379 {
380         if (xdl_prepare_env(file1, file2, xpp, env) < 0)
381                 return -1;
382
383         return histogram_diff(xpp, env,
384                 env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
385                 env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
386 }