freshlybakedca.ke
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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
52struct 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
75struct 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
91static int cmp_recs(xrecord_t *r1, xrecord_t *r2)
92{
93 return r1->ha == r2->ha;
94
95}
96
97#define CMP(i, s1, l1, s2, l2) \
98 (cmp_recs(REC(i->env, s1, l1), REC(i->env, s2, l2)))
99
100#define TABLE_HASH(index, side, line) \
101 XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
102
103static int scanA(struct histindex *index, int line1, int count1)
104{
105 unsigned int ptr, tbl_idx;
106 unsigned int chain_len;
107 struct record **rec_chain, *rec;
108
109 for (ptr = LINE_END(1); (unsigned int)line1 <= ptr; ptr--) {
110 tbl_idx = TABLE_HASH(index, 1, ptr);
111 rec_chain = index->records + tbl_idx;
112 rec = *rec_chain;
113
114 chain_len = 0;
115 while (rec) {
116 if (CMP(index, 1, rec->ptr, 1, ptr)) {
117 /*
118 * ptr is identical to another element. Insert
119 * it onto the front of the existing element
120 * chain.
121 */
122 NEXT_PTR(index, ptr) = rec->ptr;
123 rec->ptr = ptr;
124 /* cap rec->cnt at MAX_CNT */
125 rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
126 LINE_MAP(index, ptr) = rec;
127 goto continue_scan;
128 }
129
130 rec = rec->next;
131 chain_len++;
132 }
133
134 if (chain_len == index->max_chain_length)
135 return -1;
136
137 /*
138 * This is the first time we have ever seen this particular
139 * element in the sequence. Construct a new chain for it.
140 */
141 if (!(rec = xdl_cha_alloc(&index->rcha)))
142 return -1;
143 rec->ptr = ptr;
144 rec->cnt = 1;
145 rec->next = *rec_chain;
146 *rec_chain = rec;
147 LINE_MAP(index, ptr) = rec;
148
149continue_scan:
150 ; /* no op */
151 }
152
153 return 0;
154}
155
156static int try_lcs(struct histindex *index, struct region *lcs, int b_ptr,
157 int line1, int count1, int line2, int count2)
158{
159 unsigned int b_next = b_ptr + 1;
160 struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
161 unsigned int as, ae, bs, be, np, rc;
162 int should_break;
163
164 for (; rec; rec = rec->next) {
165 if (rec->cnt > index->cnt) {
166 if (!index->has_common)
167 index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
168 continue;
169 }
170
171 as = rec->ptr;
172 if (!CMP(index, 1, as, 2, b_ptr))
173 continue;
174
175 index->has_common = 1;
176 for (;;) {
177 should_break = 0;
178 np = NEXT_PTR(index, as);
179 bs = b_ptr;
180 ae = as;
181 be = bs;
182 rc = rec->cnt;
183
184 while ((unsigned int)line1 < as && (unsigned int)line2 < bs
185 && CMP(index, 1, as - 1, 2, bs - 1)) {
186 as--;
187 bs--;
188 if (1 < rc)
189 rc = XDL_MIN(rc, CNT(index, as));
190 }
191 while (ae < (unsigned int)LINE_END(1) && be < (unsigned int)LINE_END(2)
192 && CMP(index, 1, ae + 1, 2, be + 1)) {
193 ae++;
194 be++;
195 if (1 < rc)
196 rc = XDL_MIN(rc, CNT(index, ae));
197 }
198
199 if (b_next <= be)
200 b_next = be + 1;
201 if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
202 lcs->begin1 = as;
203 lcs->begin2 = bs;
204 lcs->end1 = ae;
205 lcs->end2 = be;
206 index->cnt = rc;
207 }
208
209 if (np == 0)
210 break;
211
212 while (np <= ae) {
213 np = NEXT_PTR(index, np);
214 if (np == 0) {
215 should_break = 1;
216 break;
217 }
218 }
219
220 if (should_break)
221 break;
222
223 as = np;
224 }
225 }
226 return b_next;
227}
228
229static int fall_back_to_classic_diff(xpparam_t const *xpp, xdfenv_t *env,
230 int line1, int count1, int line2, int count2)
231{
232 xpparam_t xpparam;
233
234 memset(&xpparam, 0, sizeof(xpparam));
235 xpparam.flags = xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
236
237 return xdl_fall_back_diff(env, &xpparam,
238 line1, count1, line2, count2);
239}
240
241static inline void free_index(struct histindex *index)
242{
243 xdl_free(index->records);
244 xdl_free(index->line_map);
245 xdl_free(index->next_ptrs);
246 xdl_cha_free(&index->rcha);
247}
248
249static int find_lcs(xpparam_t const *xpp, xdfenv_t *env,
250 struct region *lcs,
251 int line1, int count1, int line2, int count2)
252{
253 int b_ptr;
254 int ret = -1;
255 struct histindex index;
256
257 memset(&index, 0, sizeof(index));
258
259 index.env = env;
260 index.xpp = xpp;
261
262 index.records = NULL;
263 index.line_map = NULL;
264 /* in case of early xdl_cha_free() */
265 index.rcha.head = NULL;
266
267 index.table_bits = xdl_hashbits(count1);
268 index.records_size = 1 << index.table_bits;
269 if (!XDL_CALLOC_ARRAY(index.records, index.records_size))
270 goto cleanup;
271
272 index.line_map_size = count1;
273 if (!XDL_CALLOC_ARRAY(index.line_map, index.line_map_size))
274 goto cleanup;
275
276 if (!XDL_CALLOC_ARRAY(index.next_ptrs, index.line_map_size))
277 goto cleanup;
278
279 /* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
280 if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
281 goto cleanup;
282
283 index.ptr_shift = line1;
284 index.max_chain_length = 64;
285
286 if (scanA(&index, line1, count1))
287 goto cleanup;
288
289 index.cnt = index.max_chain_length + 1;
290
291 for (b_ptr = line2; b_ptr <= LINE_END(2); )
292 b_ptr = try_lcs(&index, lcs, b_ptr, line1, count1, line2, count2);
293
294 if (index.has_common && index.max_chain_length < index.cnt)
295 ret = 1;
296 else
297 ret = 0;
298
299cleanup:
300 free_index(&index);
301 return ret;
302}
303
304static int histogram_diff(xpparam_t const *xpp, xdfenv_t *env,
305 int line1, int count1, int line2, int count2)
306{
307 struct region lcs;
308 int lcs_found;
309 int result;
310redo:
311 result = -1;
312
313 if (count1 <= 0 && count2 <= 0)
314 return 0;
315
316 if ((unsigned int)LINE_END(1) >= MAX_PTR)
317 return -1;
318
319 if (!count1) {
320 while(count2--)
321 env->xdf2.changed[line2++ - 1] = true;
322 return 0;
323 } else if (!count2) {
324 while(count1--)
325 env->xdf1.changed[line1++ - 1] = true;
326 return 0;
327 }
328
329 memset(&lcs, 0, sizeof(lcs));
330 lcs_found = find_lcs(xpp, env, &lcs, line1, count1, line2, count2);
331 if (lcs_found < 0)
332 goto out;
333 else if (lcs_found)
334 result = fall_back_to_classic_diff(xpp, env, line1, count1, line2, count2);
335 else {
336 if (lcs.begin1 == 0 && lcs.begin2 == 0) {
337 while (count1--)
338 env->xdf1.changed[line1++ - 1] = true;
339 while (count2--)
340 env->xdf2.changed[line2++ - 1] = true;
341 result = 0;
342 } else {
343 result = histogram_diff(xpp, env,
344 line1, lcs.begin1 - line1,
345 line2, lcs.begin2 - line2);
346 if (result)
347 goto out;
348 /*
349 * result = histogram_diff(xpp, env,
350 * lcs.end1 + 1, LINE_END(1) - lcs.end1,
351 * lcs.end2 + 1, LINE_END(2) - lcs.end2);
352 * but let's optimize tail recursion ourself:
353 */
354 count1 = LINE_END(1) - lcs.end1;
355 line1 = lcs.end1 + 1;
356 count2 = LINE_END(2) - lcs.end2;
357 line2 = lcs.end2 + 1;
358 goto redo;
359 }
360 }
361out:
362 return result;
363}
364
365int xdl_do_histogram_diff(xpparam_t const *xpp, xdfenv_t *env)
366{
367 return histogram_diff(xpp, env,
368 env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
369 env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
370}