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 #include "xtypes.h"
46 #include "xdiff.h"
47 
48 #define MAX_PTR	UINT_MAX
49 #define MAX_CNT	UINT_MAX
50 
51 #define LINE_END(n) (line##n + count##n - 1)
52 #define LINE_END_PTR(n) (*line##n + *count##n - 1)
53 
54 struct histindex {
55 	struct record {
56 		unsigned int ptr, cnt;
57 		struct record *next;
58 	} **records, /* an occurrence */
59 	  **line_map; /* map of line to record chain */
60 	chastore_t rcha;
61 	unsigned int *next_ptrs;
62 	unsigned int table_bits,
63 		     records_size,
64 		     line_map_size;
65 
66 	unsigned int max_chain_length,
67 		     key_shift,
68 		     ptr_shift;
69 
70 	unsigned int cnt,
71 		     has_common;
72 
73 	xdfenv_t *env;
74 	xpparam_t const *xpp;
75 };
76 
77 struct region {
78 	unsigned int begin1, end1;
79 	unsigned int begin2, end2;
80 };
81 
82 #define LINE_MAP(i, a) (i->line_map[(a) - i->ptr_shift])
83 
84 #define NEXT_PTR(index, ptr) \
85 	(index->next_ptrs[(ptr) - index->ptr_shift])
86 
87 #define CNT(index, ptr) \
88 	((LINE_MAP(index, ptr))->cnt)
89 
90 #define REC(env, s, l) \
91 	(env->xdf##s.recs[l - 1])
92 
cmp_recs(xpparam_t const * xpp,xrecord_t * r1,xrecord_t * r2)93 static int cmp_recs(xpparam_t const *xpp,
94 	xrecord_t *r1, xrecord_t *r2)
95 {
96 	return r1->ha == r2->ha &&
97 		xdl_recmatch(r1->ptr, r1->size, r2->ptr, r2->size,
98 			    xpp->flags);
99 }
100 
101 #define CMP_ENV(xpp, env, s1, l1, s2, l2) \
102 	(cmp_recs(xpp, REC(env, s1, l1), REC(env, s2, l2)))
103 
104 #define CMP(i, s1, l1, s2, l2) \
105 	(cmp_recs(i->xpp, REC(i->env, s1, l1), REC(i->env, s2, l2)))
106 
107 #define TABLE_HASH(index, side, line) \
108 	XDL_HASHLONG((REC(index->env, side, line))->ha, index->table_bits)
109 
scanA(struct histindex * index,unsigned int line1,unsigned int count1)110 static int scanA(struct histindex *index, unsigned int line1, unsigned int count1)
111 {
112 	unsigned int ptr;
113 	unsigned int tbl_idx;
114 	unsigned int chain_len;
115 	struct record **rec_chain, *rec;
116 
117 	for (ptr = LINE_END(1); line1 <= ptr; ptr--) {
118 		tbl_idx = TABLE_HASH(index, 1, ptr);
119 		rec_chain = index->records + tbl_idx;
120 		rec = *rec_chain;
121 
122 		chain_len = 0;
123 		while (rec) {
124 			if (CMP(index, 1, rec->ptr, 1, ptr)) {
125 				/*
126 				 * ptr is identical to another element. Insert
127 				 * it onto the front of the existing element
128 				 * chain.
129 				 */
130 				NEXT_PTR(index, ptr) = rec->ptr;
131 				rec->ptr = ptr;
132 				/* cap rec->cnt at MAX_CNT */
133 				rec->cnt = XDL_MIN(MAX_CNT, rec->cnt + 1);
134 				LINE_MAP(index, ptr) = rec;
135 				goto continue_scan;
136 			}
137 
138 			rec = rec->next;
139 			chain_len++;
140 		}
141 
142 		if (chain_len == index->max_chain_length)
143 			return -1;
144 
145 		/*
146 		 * This is the first time we have ever seen this particular
147 		 * element in the sequence. Construct a new chain for it.
148 		 */
149 		if (!(rec = xdl_cha_alloc(&index->rcha)))
150 			return -1;
151 		rec->ptr = ptr;
152 		rec->cnt = 1;
153 		rec->next = *rec_chain;
154 		*rec_chain = rec;
155 		LINE_MAP(index, ptr) = rec;
156 
157 continue_scan:
158 		; /* no op */
159 	}
160 
161 	return 0;
162 }
163 
try_lcs(struct histindex * index,struct region * lcs,unsigned int b_ptr,unsigned int line1,unsigned int count1,unsigned int line2,unsigned int count2)164 static int try_lcs(
165 	struct histindex *index, struct region *lcs, unsigned int b_ptr,
166 	unsigned int line1, unsigned int count1,
167 	unsigned int line2, unsigned int count2)
168 {
169 	unsigned int b_next = b_ptr + 1;
170 	struct record *rec = index->records[TABLE_HASH(index, 2, b_ptr)];
171 	unsigned int as, ae, bs, be, np, rc;
172 	int should_break;
173 
174 	for (; rec; rec = rec->next) {
175 		if (rec->cnt > index->cnt) {
176 			if (!index->has_common)
177 				index->has_common = CMP(index, 1, rec->ptr, 2, b_ptr);
178 			continue;
179 		}
180 
181 		as = rec->ptr;
182 		if (!CMP(index, 1, as, 2, b_ptr))
183 			continue;
184 
185 		index->has_common = 1;
186 		for (;;) {
187 			should_break = 0;
188 			np = NEXT_PTR(index, as);
189 			bs = b_ptr;
190 			ae = as;
191 			be = bs;
192 			rc = rec->cnt;
193 
194 			while (line1 < as && line2 < bs
195 				&& CMP(index, 1, as - 1, 2, bs - 1)) {
196 				as--;
197 				bs--;
198 				if (1 < rc)
199 					rc = XDL_MIN(rc, CNT(index, as));
200 			}
201 			while (ae < LINE_END(1) && be < LINE_END(2)
202 				&& CMP(index, 1, ae + 1, 2, be + 1)) {
203 				ae++;
204 				be++;
205 				if (1 < rc)
206 					rc = XDL_MIN(rc, CNT(index, ae));
207 			}
208 
209 			if (b_next <= be)
210 				b_next = be + 1;
211 			if (lcs->end1 - lcs->begin1 < ae - as || rc < index->cnt) {
212 				lcs->begin1 = as;
213 				lcs->begin2 = bs;
214 				lcs->end1 = ae;
215 				lcs->end2 = be;
216 				index->cnt = rc;
217 			}
218 
219 			if (np == 0)
220 				break;
221 
222 			while (np <= ae) {
223 				np = NEXT_PTR(index, np);
224 				if (np == 0) {
225 					should_break = 1;
226 					break;
227 				}
228 			}
229 
230 			if (should_break)
231 				break;
232 
233 			as = np;
234 		}
235 	}
236 	return b_next;
237 }
238 
find_lcs(struct histindex * index,struct region * lcs,unsigned int line1,unsigned int count1,unsigned int line2,unsigned int count2)239 static int find_lcs(
240 	struct histindex *index, struct region *lcs,
241 	unsigned int line1, unsigned int count1,
242 	unsigned int line2, unsigned int count2)
243 {
244 	unsigned int b_ptr;
245 
246 	if (scanA(index, line1, count1))
247 		return -1;
248 
249 	index->cnt = index->max_chain_length + 1;
250 
251 	for (b_ptr = line2; b_ptr <= LINE_END(2); )
252 		b_ptr = try_lcs(index, lcs, b_ptr, line1, count1, line2, count2);
253 
254 	return index->has_common && index->max_chain_length < index->cnt;
255 }
256 
fall_back_to_classic_diff(struct histindex * index,int line1,int count1,int line2,int count2)257 static int fall_back_to_classic_diff(struct histindex *index,
258 		int line1, int count1, int line2, int count2)
259 {
260 	xpparam_t xpp;
261 	xpp.flags = index->xpp->flags & ~XDF_DIFF_ALGORITHM_MASK;
262 
263 	return xdl_fall_back_diff(index->env, &xpp,
264 				  line1, count1, line2, count2);
265 }
266 
histogram_diff(xpparam_t const * xpp,xdfenv_t * env,unsigned int line1,unsigned int count1,unsigned int line2,unsigned int count2)267 static int histogram_diff(
268 	xpparam_t const *xpp, xdfenv_t *env,
269 	unsigned int line1, unsigned int count1,
270 	unsigned int line2, unsigned int count2)
271 {
272 	struct histindex index;
273 	struct region lcs;
274 	size_t sz;
275 	int result = -1;
276 
277 	if (count1 <= 0 && count2 <= 0)
278 		return 0;
279 
280 	if (LINE_END(1) >= MAX_PTR)
281 		return -1;
282 
283 	if (!count1) {
284 		while(count2--)
285 			env->xdf2.rchg[line2++ - 1] = 1;
286 		return 0;
287 	} else if (!count2) {
288 		while(count1--)
289 			env->xdf1.rchg[line1++ - 1] = 1;
290 		return 0;
291 	}
292 
293 	memset(&index, 0, sizeof(index));
294 
295 	index.env = env;
296 	index.xpp = xpp;
297 
298 	index.records = NULL;
299 	index.line_map = NULL;
300 	/* in case of early xdl_cha_free() */
301 	index.rcha.head = NULL;
302 
303 	index.table_bits = xdl_hashbits(count1);
304 	sz = index.records_size = 1 << index.table_bits;
305 	GIT_ERROR_CHECK_ALLOC_MULTIPLY(&sz, sz, sizeof(struct record *));
306 
307 	if (!(index.records = (struct record **) xdl_malloc(sz)))
308 		goto cleanup;
309 	memset(index.records, 0, sz);
310 
311 	sz = index.line_map_size = count1;
312 	sz *= sizeof(struct record *);
313 	if (!(index.line_map = (struct record **) xdl_malloc(sz)))
314 		goto cleanup;
315 	memset(index.line_map, 0, sz);
316 
317 	sz = index.line_map_size;
318 	sz *= sizeof(unsigned int);
319 	if (!(index.next_ptrs = (unsigned int *) xdl_malloc(sz)))
320 		goto cleanup;
321 	memset(index.next_ptrs, 0, sz);
322 
323 	/* lines / 4 + 1 comes from xprepare.c:xdl_prepare_ctx() */
324 	if (xdl_cha_init(&index.rcha, sizeof(struct record), count1 / 4 + 1) < 0)
325 		goto cleanup;
326 
327 	index.ptr_shift = line1;
328 	index.max_chain_length = 64;
329 
330 	memset(&lcs, 0, sizeof(lcs));
331 	if (find_lcs(&index, &lcs, line1, count1, line2, count2))
332 		result = fall_back_to_classic_diff(&index, line1, count1, line2, count2);
333 	else {
334 		if (lcs.begin1 == 0 && lcs.begin2 == 0) {
335 			while (count1--)
336 				env->xdf1.rchg[line1++ - 1] = 1;
337 			while (count2--)
338 				env->xdf2.rchg[line2++ - 1] = 1;
339 			result = 0;
340 		} else {
341 			result = histogram_diff(xpp, env,
342 						line1, lcs.begin1 - line1,
343 						line2, lcs.begin2 - line2);
344 			if (result)
345 				goto cleanup;
346 			result = histogram_diff(xpp, env,
347 						lcs.end1 + 1, LINE_END(1) - lcs.end1,
348 						lcs.end2 + 1, LINE_END(2) - lcs.end2);
349 			if (result)
350 				goto cleanup;
351 		}
352 	}
353 
354 cleanup:
355 	xdl_free(index.records);
356 	xdl_free(index.line_map);
357 	xdl_free(index.next_ptrs);
358 	xdl_cha_free(&index.rcha);
359 
360 	return result;
361 }
362 
xdl_do_histogram_diff(mmfile_t * file1,mmfile_t * file2,xpparam_t const * xpp,xdfenv_t * env)363 int xdl_do_histogram_diff(mmfile_t *file1, mmfile_t *file2,
364 	xpparam_t const *xpp, xdfenv_t *env)
365 {
366 	if (xdl_prepare_env(file1, file2, xpp, env) < 0)
367 		return -1;
368 
369 	return histogram_diff(xpp, env,
370 		env->xdf1.dstart + 1, env->xdf1.dend - env->xdf1.dstart + 1,
371 		env->xdf2.dstart + 1, env->xdf2.dend - env->xdf2.dstart + 1);
372 }
373